Why won't my meter check this?

[John Fields]

On Fri, 28 Mar 2014 18:14:03 -0500, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <7m3bj91kjksudlthedibu14djgja9a3mq4@4ax.com>,
jfields@austininstruments.com says...
Consequently, I posted a circuit which would allow him to vary the
current through the diode while watching the drop across it on the
meter supplying the current.

What's wrong with that?

---
Oops...

I just spotted a glaring technical error in the next to last
sentence; can you tell what it is?




A dog always smells their own stench first!

Jamie

---
The better to fend off the smart fellers.

 

[Jim Thompson]

On Fri, 28 Mar 2014 18:18:20 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Fri, 28 Mar 2014 18:14:03 -0500, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <7m3bj91kjksudlthedibu14djgja9a3mq4@4ax.com>,
jfields@austininstruments.com says...
Consequently, I posted a circuit which would allow him to vary the
current through the diode while watching the drop across it on the
meter supplying the current.

What's wrong with that?

---
Oops...

I just spotted a glaring technical error in the next to last
sentence; can you tell what it is?




A dog always smells their own stench first!

Jamie

---
The better to fend off the smart fellers.

Jamie is a Larkin sycophant, _and_ infinitely incompetent... need one
say anything more?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Maynard A. Philbrook Jr.]

In article <oi4cj9tg0vebgvi8ogvflm5lpgukre57sj@4ax.com>, To-Email-Use-
The-Envelope-Icon@On-My-Web-Site.com says...

Oops...

I just spotted a glaring technical error in the next to last
sentence; can you tell what it is?




A dog always smells their own stench first!

Jamie

---
The better to fend off the smart fellers.

Jamie is a Larkin sycophant, _and_ infinitely incompetent... need one
say anything more?

...Jim Thompson
--

So by your own admission, you'd expect the audience to
take that as a highly accurate non conflicting judgment?

I am not "Wag the Dog" but I sure see a few that think they
are.

Jamie

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403251458190.11074@darkstar.example.org...

On Tue, 25 Mar 2014, etpm@whidbey.com wrote:

I have a DVM made by Extech that has the diode check function. When
checking a regular diode the function works. But when I try an LED it
shows open both ways. And when I try to measure resistance the meter
shows open both ways. Is it possible that the LEDs just need more
current before than the meter provides they will conduct?
Thanks,
Eric

LEDs need more voltage, and the more esoteric the color, the higher the
voltage.

Allegedly; the green LED is a pretty good 2V reference.

In the late 80'S one of the Thorn Consumer Electronics TVs used one for a
reference on the CRT base panel.

 

[Ian Field]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:ckg8j91rlm8jvvs2ohds3e3c27s05vn4r8@4ax.com...

On Thu, 27 Mar 2014 18:16:15 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"John Fields"
"Phil Allison"

etpm@whidbey.com

I don't know what the voltage diode test function uses.


** It uses a fixed current ( like 1mA) - then it reads the voltage.

I'll check it.

** With what ?

---

+------ + +------+
| -->||---[R]---|mA |
| | | |
| COM|---------|COM |
+-------+ +------+
DIODE 2mA
TEST

** You over snipped the post and CHANGED the meaning !!!

The OP said he was going test the *VOLTAGE* of his Extech meter.

I asked " with what " - because he seems to have only one meter.

Capice ???


.... Phil



Put the meter on the diode test range.

Connect it to an electrolytic capacitor for an hour maybe. 100 uF
ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

 

[John Fields]

On Sat, 29 Mar 2014 21:39:39 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:ckg8j91rlm8jvvs2ohds3e3c27s05vn4r8@4ax.com...
On Thu, 27 Mar 2014 18:16:15 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"John Fields"
"Phil Allison"

etpm@whidbey.com

I don't know what the voltage diode test function uses.


** It uses a fixed current ( like 1mA) - then it reads the voltage.

I'll check it.

** With what ?

---

+------ + +------+
| -->||---[R]---|mA |
| | | |
| COM|---------|COM |
+-------+ +------+
DIODE 2mA
TEST

** You over snipped the post and CHANGED the meaning !!!

The OP said he was going test the *VOLTAGE* of his Extech meter.

I asked " with what " - because he seems to have only one meter.

Capice ???


.... Phil



Put the meter on the diode test range.

Connect it to an electrolytic capacitor for an hour maybe. 100 uF
ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

---
Depending on what's being used to make the shutdown decision,
whether it has auto shutdown or not may be irrelevant.

Try it.

 

[John Fields]

On Sat, 29 Mar 2014 21:36:30 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403251458190.11074@darkstar.example.org...
On Tue, 25 Mar 2014, etpm@whidbey.com wrote:

I have a DVM made by Extech that has the diode check function. When
checking a regular diode the function works. But when I try an LED it
shows open both ways. And when I try to measure resistance the meter
shows open both ways. Is it possible that the LEDs just need more
current before than the meter provides they will conduct?
Thanks,
Eric

LEDs need more voltage, and the more esoteric the color, the higher the
voltage.

Allegedly; the green LED is a pretty good 2V reference.

---
It's just a diode working in quadrant I of the VI curve, so it's no
better a "reference" than any other forward-biased diode, it just
happens to conveniently drop 2V with a peculiar current forced
through it.

 

[Michael Black]

On Sat, 29 Mar 2014, Ian Field wrote:

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403251458190.11074@darkstar.example.org...
On Tue, 25 Mar 2014, etpm@whidbey.com wrote:

I have a DVM made by Extech that has the diode check function. When
checking a regular diode the function works. But when I try an LED it
shows open both ways. And when I try to measure resistance the meter
shows open both ways. Is it possible that the LEDs just need more
current before than the meter provides they will conduct?
Thanks,
Eric

LEDs need more voltage, and the more esoteric the color, the higher the
voltage.

Allegedly; the green LED is a pretty good 2V reference.

In the late 80'S one of the Thorn Consumer Electronics TVs used one for a
reference on the CRT base panel.

I remember that sort of thing, I don't remember if they were said to be a
good reference or just a handy low voltage "zener".

I am reminded of an article that was about a radio synthesizer, and the
author suggested using a common switching diode as the varactor, since the
runing range was fairly small. But then he warns "I had endless problems
with 60Hz modulation, until I realized that the glass cased switching
diode was under the desk lamp and was being modulated by it. A switch to
a non-clear cased diode, or just a bit of electrical tape, solved the
problem".

Michael

 

[Michael Black]

On Sat, 29 Mar 2014, Ian Field wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:ckg8j91rlm8jvvs2ohds3e3c27s05vn4r8@4ax.com...
On Thu, 27 Mar 2014 18:16:15 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"John Fields"
"Phil Allison"

etpm@whidbey.com

I don't know what the voltage diode test function uses.


** It uses a fixed current ( like 1mA) - then it reads the voltage.

I'll check it.

** With what ?

---

+------ + +------+
| -->||---[R]---|mA |
| | | |
| COM|---------|COM |
+-------+ +------+
DIODE 2mA
TEST

** You over snipped the post and CHANGED the meaning !!!

The OP said he was going test the *VOLTAGE* of his Extech meter.

I asked " with what " - because he seems to have only one meter.

Capice ???


.... Phil



Put the meter on the diode test range.

Connect it to an electrolytic capacitor for an hour maybe. 100 uF ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael

 

[Maynard A. Philbrook Jr.]

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...

Connect it to an electrolytic capacitor for an hour maybe. 100 uF ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael

Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403300045330.21634@darkstar.example.org...

On Sat, 29 Mar 2014, Ian Field wrote:



"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403251458190.11074@darkstar.example.org...
On Tue, 25 Mar 2014, etpm@whidbey.com wrote:

I have a DVM made by Extech that has the diode check function. When
checking a regular diode the function works. But when I try an LED it
shows open both ways. And when I try to measure resistance the meter
shows open both ways. Is it possible that the LEDs just need more
current before than the meter provides they will conduct?
Thanks,
Eric

LEDs need more voltage, and the more esoteric the color, the higher the
voltage.

Allegedly; the green LED is a pretty good 2V reference.

In the late 80'S one of the Thorn Consumer Electronics TVs used one for
a reference on the CRT base panel.
I remember that sort of thing, I don't remember if they were said to be a
good reference or just a handy low voltage "zener".

According to the service manual; there was something in particular about a
green LED as a reference as the reason TCE used it.

Green LEDs are a favourite for the base stabiliser in single transistor
current sources - but then lots of people use red LEDs as well.

 

[John Fields]

On Sun, 30 Mar 2014 09:31:25 -0500, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...
Connect it to an electrolytic capacitor for an hour maybe. 100 uF ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael



Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

---
So you could be in the middle of a reading or recording a trend and
the thing would just turn off?

John Fields

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1403300043530.21634@darkstar.example.org...

On Sat, 29 Mar 2014, Ian Field wrote:



"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message news:ckg8j91rlm8jvvs2ohds3e3c27s05vn4r8@4ax.com...
On Thu, 27 Mar 2014 18:16:15 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"John Fields"
"Phil Allison"

etpm@whidbey.com

I don't know what the voltage diode test function uses.


** It uses a fixed current ( like 1mA) - then it reads the voltage.

I'll check it.

** With what ?

---

+------ + +------+
| -->||---[R]---|mA |
| | | |
| COM|---------|COM |
+-------+ +------+
DIODE 2mA
TEST

** You over snipped the post and CHANGED the meaning !!!

The OP said he was going test the *VOLTAGE* of his Extech meter.

I asked " with what " - because he seems to have only one meter.

Capice ???


.... Phil



Put the meter on the diode test range.

Connect it to an electrolytic capacitor for an hour maybe. 100 uF
ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.
My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

The meter I use most often has various buttons for data-hold etc, if I push
one of those periodically it resets the PWR timeout.

Might be worth looking into those "ready to use" Ni-Mh batteries that are
claimed to hold 75% for a year, won't last as long as alkaline (before
needing recharge) - but should be safe from leaks.

 

[Ian Field]

"Maynard A. Philbrook Jr." <jamie_ka1lpa@charter.net> wrote in message
news:MPG.2da1f4cba9d11c41989833@news.eternal-september.org...

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...
Connect it to an electrolytic capacitor for an hour maybe. 100 uF
ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something
off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael



Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on,

My old Taylor analogue grew an extra button when the 30V high-Ohms range
battery became unobtainable.

That battery compartment is now occupied by a blocking oscillator/inverter
that runs from the low-Ohms range D cell.

 

[John Larkin]

On Sun, 30 Mar 2014 11:29:04 -0500, John Fields <jfields@austininstruments.com>
wrote:

On Sun, 30 Mar 2014 09:31:25 -0500, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...
Connect it to an electrolytic capacitor for an hour maybe. 100 uF ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael



Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

---
So you could be in the middle of a reading or recording a trend and
the thing would just turn off?

John Fields

Most of the handhelds do that nowadays.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Ian Field]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:llkgj9dildt5gs7nvn3lnqf4njcdpfimdp@4ax.com...

On Sun, 30 Mar 2014 11:29:04 -0500, John Fields
jfields@austininstruments.com
wrote:

On Sun, 30 Mar 2014 09:31:25 -0500, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...
Connect it to an electrolytic capacitor for an hour maybe. 100 uF
ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something
off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael



Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

---
So you could be in the middle of a reading or recording a trend and
the thing would just turn off?

John Fields

Most of the handhelds do that nowadays.

Mine is *supposed* to remain active if there's a varying reading in
progress - not the most reliable feature!

 

[Maynard A. Philbrook Jr.]

In article <echgj9972ogofl51u2fr692i6k0vfb6f37@4ax.com>,
jfields@austininstruments.com says...

Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

---
So you could be in the middle of a reading or recording a trend and
the thing would just turn off?

John Fields

absolutely.

Jamie

 

[Maynard A. Philbrook Jr.]

In article <llkgj9dildt5gs7nvn3lnqf4njcdpfimdp@4ax.com>,
jjlarkin@highNOTlandTHIStechnologyPART.com says...

On Sun, 30 Mar 2014 11:29:04 -0500, John Fields <jfields@austininstruments.com
wrote:

On Sun, 30 Mar 2014 09:31:25 -0500, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <alpine.LNX.2.02.1403300043530.21634@darkstar.example.org>,
et472@ncf.ca says...
Connect it to an electrolytic capacitor for an hour maybe. 100 uF ballpark.

All my DMMs have auto shutdown after a few minutes - YMMV.

My good one doesn't, as I discovered this week when I pulled something off
it and discovered I'd left it on, and now the batteries dead. I swear I
wear out the batteries that way on that DMM a lot.

Luckily, the batteries didn't leak.

Michael



Years ago I had a meter that I would forget and leave on, so I modified
the circuit with a permanent magnetic latching relay, it would turn off
automatically for me, and I simply added a push button when needed to
turn it back on, via the other side of the magnetic relay..

I used a 555 timer into a scaler IC.

Jamie

---
So you could be in the middle of a reading or recording a trend and
the thing would just turn off?

John Fields

Most of the handhelds do that nowadays.

You see what he's missing here is, simply depressing
the same button would reset the scaler back to 0 and
all I had to do was hold it down to turn off the meter.

Jamie

 

[Maynard A. Philbrook Jr.]

In article <3wYZu.87306$Iu4.76181@fx12.am4>,
gangprobing.alien@ntlworld.com says...

John Fields

Most of the handhelds do that nowadays.

Mine is *supposed* to remain active if there's a varying reading in
progress - not the most reliable feature!

Most do reset their timers if it's obvious the
unit is being used..

My Fluke 289 hand meter allows you to customize
the why that works. Time set or just stay on..


Jamie