Error of % + digits?...

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Commander Kinsey]

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never go through them. And what idiot turns the dial while it\'s connected?!

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Commander Kinsey]

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never go through them. And what idiot turns the dial while it\'s connected?!

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Commander Kinsey]

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never go through them. And what idiot turns the dial while it\'s connected?!

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

> And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery (or some other low
impedance high current voltage source).

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

> And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery (or some other low
impedance high current voltage source).

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong.com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

> And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery (or some other low
impedance high current voltage source).

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

 

[Commander Kinsey]

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org..jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong..com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances..

Then don\'t make them like that.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

Then have a gap which is connected to nothing.

And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery

Wrong. You adjust the dial to what you want to do, not remembering what you were measuring yesterday. Having only one thing to change makes it way easier to get it right.

> (or some other low impedance high current voltage source).

It only has to get over 20 amps to fuck the meter.

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

Meters should always auto range. Mine all do, and I\'ve never even considered adjusting the dial while it\'s connected. I\'m not going to change between resistance, current, and volts and want to leave it connected to the same thing.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\".

No, because you save on an extra socket.

And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

Latching relays use very little indeed, like the one in my room thermostat. 2 AA batteries last years.

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

Then they\'re fools, because now \"user can obtain short circuit by forgetting he was measuring current yesterday, or because a colleague was without him knowing\". If it was selected on the dial, there is no possibility to make a mistake. You select what you want and that\'s what you get. It\'s illogical to have one thing pointing at volts while another thing is expecting current!

Anyway, a simple fuse would solve all this. All you lose if you make a mistake is a fuse, not the internal workings of the meter, the test leads, the thing you\'re testing, and possibly your face.

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage.

Nope. I pick up a multimeter and set it to what I\'m about to measure. Same way as I don\'t drive into my house because I left my car in forward gear yesterday.

It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

People make mistakes. The best equipment prevents this. My VW Golf for example would not allow me to select 1st gear when going 100mph. It was quite clever in fact. I could do that on purpose and it would drop one gear at a time to slow the car as quickly as possible to assist the brakes in an emergency. And yes I did try it a few times, one time I scared the shit out of the passenger (who had never seen an automatic gearbox before).

 

[Commander Kinsey]

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org..jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong..com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances..

Then don\'t make them like that.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

Then have a gap which is connected to nothing.

And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery

Wrong. You adjust the dial to what you want to do, not remembering what you were measuring yesterday. Having only one thing to change makes it way easier to get it right.

> (or some other low impedance high current voltage source).

It only has to get over 20 amps to fuck the meter.

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

Meters should always auto range. Mine all do, and I\'ve never even considered adjusting the dial while it\'s connected. I\'m not going to change between resistance, current, and volts and want to leave it connected to the same thing.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\".

No, because you save on an extra socket.

And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

Latching relays use very little indeed, like the one in my room thermostat. 2 AA batteries last years.

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

Then they\'re fools, because now \"user can obtain short circuit by forgetting he was measuring current yesterday, or because a colleague was without him knowing\". If it was selected on the dial, there is no possibility to make a mistake. You select what you want and that\'s what you get. It\'s illogical to have one thing pointing at volts while another thing is expecting current!

Anyway, a simple fuse would solve all this. All you lose if you make a mistake is a fuse, not the internal workings of the meter, the test leads, the thing you\'re testing, and possibly your face.

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage.

Nope. I pick up a multimeter and set it to what I\'m about to measure. Same way as I don\'t drive into my house because I left my car in forward gear yesterday.

It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

People make mistakes. The best equipment prevents this. My VW Golf for example would not allow me to select 1st gear when going 100mph. It was quite clever in fact. I could do that on purpose and it would drop one gear at a time to slow the car as quickly as possible to assist the brakes in an emergency. And yes I did try it a few times, one time I scared the shit out of the passenger (who had never seen an automatic gearbox before).

 

[Commander Kinsey]

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 17 Jul 2020 15:02:16 +0100, Rich <rich@example.invalid> wrote:

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org..jp> wrote:
On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rheilly@bigslong..com> wrote:

On 2/07/2020 10:41 pm, Ralph Mowery wrote:
For a real scare you should see some of the safety movies that
Fluke put out. They show under test conditions what can hapen to
inexpensive meters and their meters under different conditions like
having the meter set for amps and putting across a 480 volt circuit
that has plenty of amps .

Ahh the old \"Leaving it on amps\" trick. How many of us can say they
never did it ?

I find it crazy that you can select volts and have the wires in the
amps holes. The switch should change the contacts. I\'ve broken a
meter doing that, just measuring the voltage on a car battery. £100
meter, but UNFUSED FFS! At least the mA range was fused, but they
couldn\'t be bothered putting in a 20A fuse for the big range....

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never
go through them.

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no \"end of the dial\" in those instances..

Then don\'t make them like that.

And even with an \'end of the dial\' there is still the possibility of
landing \'off by one\' while turning the dial.

Then have a gap which is connected to nothing.

And what idiot turns the dial while it\'s connected?!

The same idiot who\'d leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery

Wrong. You adjust the dial to what you want to do, not remembering what you were measuring yesterday. Having only one thing to change makes it way easier to get it right.

> (or some other low impedance high current voltage source).

It only has to get over 20 amps to fuck the meter.

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

Meters should always auto range. Mine all do, and I\'ve never even considered adjusting the dial while it\'s connected. I\'m not going to change between resistance, current, and volts and want to leave it connected to the same thing.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\".

No, because you save on an extra socket.

And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

Latching relays use very little indeed, like the one in my room thermostat. 2 AA batteries last years.

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

Then they\'re fools, because now \"user can obtain short circuit by forgetting he was measuring current yesterday, or because a colleague was without him knowing\". If it was selected on the dial, there is no possibility to make a mistake. You select what you want and that\'s what you get. It\'s illogical to have one thing pointing at volts while another thing is expecting current!

Anyway, a simple fuse would solve all this. All you lose if you make a mistake is a fuse, not the internal workings of the meter, the test leads, the thing you\'re testing, and possibly your face.

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage.

Nope. I pick up a multimeter and set it to what I\'m about to measure. Same way as I don\'t drive into my house because I left my car in forward gear yesterday.

It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

People make mistakes. The best equipment prevents this. My VW Golf for example would not allow me to select 1st gear when going 100mph. It was quite clever in fact. I could do that on purpose and it would drop one gear at a time to slow the car as quickly as possible to assist the brakes in an emergency. And yes I did try it a few times, one time I scared the shit out of the passenger (who had never seen an automatic gearbox before).

 

[Ralph Mowery]

In article <ret1h6$stk$1@dont-email.me>, rich@example.invalid says...

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
\'real\' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

 

[Ralph Mowery]

In article <ret1h6$stk$1@dont-email.me>, rich@example.invalid says...

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
\'real\' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

 

[Commander Kinsey]

On Fri, 17 Jul 2020 23:07:43 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote:

In article <ret1h6$stk$1@dont-email.me>, rich@example.invalid says...

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
\'real\' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

Better to use something that draws bit of current, like one of those screwdrivers that lights a neon through your capacitance.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

With a bad fuse it doesn\'t blow up?

 

[Commander Kinsey]

On Fri, 17 Jul 2020 23:07:43 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote:

In article <ret1h6$stk$1@dont-email.me>, rich@example.invalid says...

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
\'real\' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

Better to use something that draws bit of current, like one of those screwdrivers that lights a neon through your capacitance.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

With a bad fuse it doesn\'t blow up?

 

[Ralph Mowery]

In article <ret1h6$stk$1@dont-email.me>, rich@example.invalid says...

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that \"relay\". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of \"user must
deliberately move lead to obtain short circuit through meter\".

As well, the user who\'d leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don\'t pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
\'real\' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:
As well, the user who\'d leave the leads plugged into amps, and then
try to measure voltage on car battery or other high current source
is also just as likely to leave the range switch in the amps setting
(after having measured current somewhere) and subsequently try to
measure voltage.

Nope. I pick up a multimeter and set it to what I\'m about to
measure. Same way as I don\'t drive into my house because I left my
car in forward gear yesterday.

Interesting....

Yet you said this yesterday:

From: \"Commander Kinsey\" <CFKinsey@military.org.jp>
Date: Thu, 16 Jul 2020 20:09:20 +0100
Message-ID: <op.0nu3hup8wdg98l@glass>

....

I find it crazy that you can select volts and have the wires in the
amps holes. ... I\'ve broken a meter doing that, just measuring the
voltage on a car battery. A £100 meter, but UNFUSED FFS!

....

One aspect of \"set it to what I\'m about to measure\" should normally
include: \"are the leads in the correct jacks\".

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:
As well, the user who\'d leave the leads plugged into amps, and then
try to measure voltage on car battery or other high current source
is also just as likely to leave the range switch in the amps setting
(after having measured current somewhere) and subsequently try to
measure voltage.

Nope. I pick up a multimeter and set it to what I\'m about to
measure. Same way as I don\'t drive into my house because I left my
car in forward gear yesterday.

Interesting....

Yet you said this yesterday:

From: \"Commander Kinsey\" <CFKinsey@military.org.jp>
Date: Thu, 16 Jul 2020 20:09:20 +0100
Message-ID: <op.0nu3hup8wdg98l@glass>

....

I find it crazy that you can select volts and have the wires in the
amps holes. ... I\'ve broken a meter doing that, just measuring the
voltage on a car battery. A £100 meter, but UNFUSED FFS!

....

One aspect of \"set it to what I\'m about to measure\" should normally
include: \"are the leads in the correct jacks\".

 

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKinsey@military.org.jp> wrote:

On Fri, 17 Jul 2020 21:26:15 +0100, Rich <rich@example.invalid> wrote:
As well, the user who\'d leave the leads plugged into amps, and then
try to measure voltage on car battery or other high current source
is also just as likely to leave the range switch in the amps setting
(after having measured current somewhere) and subsequently try to
measure voltage.

Nope. I pick up a multimeter and set it to what I\'m about to
measure. Same way as I don\'t drive into my house because I left my
car in forward gear yesterday.

Interesting....

Yet you said this yesterday:

From: \"Commander Kinsey\" <CFKinsey@military.org.jp>
Date: Thu, 16 Jul 2020 20:09:20 +0100
Message-ID: <op.0nu3hup8wdg98l@glass>

....

I find it crazy that you can select volts and have the wires in the
amps holes. ... I\'ve broken a meter doing that, just measuring the
voltage on a car battery. A £100 meter, but UNFUSED FFS!

....

One aspect of \"set it to what I\'m about to measure\" should normally
include: \"are the leads in the correct jacks\".