Another question...

D

Dave

Guest
The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a voltage
meter that comes with some resistors used for setting it to the proper range
for whatever the user wants. And it only has two pins for input (I haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is it
likely that this does its job through the use of comparators, or some such,
and maybe it really doesn't contain an A/D converter chip? Or can I likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

Thanks.

Dave
 
On Tue, 1 Apr 2008, Dave wrote:

The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a voltage
meter that comes with some resistors used for setting it to the proper range
for whatever the user wants. And it only has two pins for input (I haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is it
likely that this does its job through the use of comparators, or some such,
and maybe it really doesn't contain an A/D converter chip? Or can I likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Who knows what he means. If it's a digital meter, then of courese
Click to expand...
there's some sort of analog to digital conversion. The specifics of
how it's done (which may confuse people like the salesman) doesn't matter
to the end user.

A panel meter is just that, a meter intended for mounting on a panel.
They had them in the days of analog meters, they have them in the
days of digital meters. All it means is a fixed range meter.

Any DMM has that sort of thing deep inside it, the difference being the
DMM is multi-range and multi-function so it adds switching ahead of the
"panel meter"/fixed range meter to divide input voltage to a range that
the meter can handle, and adds things like a current source for measuring
resistors and semiconductor junctions, and adds some sort of AC to DC
conversion circuitry to allow for measuring AC voltages, and adds a shunt
resistor so you can measure the voltage drop across that shunt resistor to
measure current through a circuit.

As long as the voltage range of the panel meter is sensitive enough for
your needs, then it should be fine. If you need really find sensitivity,
you may need to look further. If you need to measure larger voltages,
then that's taken care of with a couple of resistors acting as a voltage
divider.

Of course, for hobby use the only real advantage of buying a digital
panel meter is size. SInce you can get DMMs for as low as ten dollars,
that may be the cheapest way to get a digital meter, placing it behind
your project panel and treating it as a fixed range panel meter. But the
actual panel meter is bound to be smaller.

Michael
 
"Dave" <db5151@hotmail.com> wrote in message
news:jtednb1FFZ28pG_anZ2dnUVZ_jqdnZ2d@internetamerica...
The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage
meter that comes with some resistors used for setting it to the proper
range
for whatever the user wants. And it only has two pins for input (I
haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is
it
likely that this does its job through the use of comparators, or some
such,
and maybe it really doesn't contain an A/D converter chip? Or can I
likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

Thanks.

Dave
Click to expand...
It has to have an A/D converter to convert the 0 to 200mv analog input to
digital.. Most likely it is a single chip solution using a microprocessor
or some sort of custom array. Included in the processor is a 10bit A/D to do
the conversion. In the processor code, the digital data is converted to BCD
for driving the LCD digit segments in a matrix. The segments are driven by
switched AC voltage also generated by the processor. RAM in the processor
holds the converted value indefinitely for continuous display. Look up
tables are likely used to determine what segments to display for a given
conversion value.

There is a lot going on but it is all done in processor code. This cheap
meter illustrates the power of processors in modern electronics. If this
were done with discrete hardware components, A/D, flip-flops, gates, RAM,
display drivers and the rest it would be on a large board costing hundreds
of dollars.
 
On Tue, 1 Apr 2008, Bob Eld wrote:

"Dave" <db5151@hotmail.com> wrote in message
news:jtednb1FFZ28pG_anZ2dnUVZ_jqdnZ2d@internetamerica...
The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage
meter that comes with some resistors used for setting it to the proper
range
for whatever the user wants. And it only has two pins for input (I
haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is
it
likely that this does its job through the use of comparators, or some
such,
and maybe it really doesn't contain an A/D converter chip? Or can I
likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

Thanks.

Dave

It has to have an A/D converter to convert the 0 to 200mv analog input to
digital.. Most likely it is a single chip solution using a microprocessor
or some sort of custom array. Included in the processor is a 10bit A/D to do
the conversion. In the processor code, the digital data is converted to BCD
for driving the LCD digit segments in a matrix. The segments are driven by
switched AC voltage also generated by the processor. RAM in the processor
holds the converted value indefinitely for continuous display. Look up
tables are likely used to determine what segments to display for a given
conversion value.

There is a lot going on but it is all done in processor code. This cheap
meter illustrates the power of processors in modern electronics. If this
were done with discrete hardware components, A/D, flip-flops, gates, RAM,
display drivers and the rest it would be on a large board costing hundreds
of dollars.

But wait.
Click to expand...

Thirty years ago I bought an Intersil evaluation kit for their just
released digital voltmeter IC, I guess it was the 7107. I paid fifty
dollars for it in Canada, and when built it made a nice panel meter.

That was a big step forward, it did allow for a DVM at a much lower
cost at the time. But it sure wasn't a CPU in there, it just better
integrated what had come before.

Even before that, there were multiple IC sets that went together
to make a DVM, the Intersil just moved forward a tad.

Now, they may use CPUs in there now if there is some good reason to
make it changeable by changing the code, but thirty years ago you
could get a DVM in a single IC. And that IC, or others like it,
are what's inside most DMMs, which is precisely why they got cheap.

I paid about eighty dollars for my first DMM in 1984, and that was
about as cheap as they came back then. You can now get them for
ten dollars, which is the result of thirty years of volume and
displacement of analog meters.

Michael
 
"Dave" <db5151@hotmail.com> schreef in bericht
news:jtednb1FFZ28pG_anZ2dnUVZ_jqdnZ2d@internetamerica...
The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage meter that comes with some resistors used for setting it to the
proper range for whatever the user wants. And it only has two pins for
input (I haven't actually seen it yet, so I am quoting what he told me.)
*He* says it doesn't contain an A/D converter, it's just a meter (?) My
question: is it likely that this does its job through the use of
comparators, or some such, and maybe it really doesn't contain an A/D
converter chip? Or can I likely buy this, break into and modify it, and
then use it as the readout for my transistor tester, showing the gain of
the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

Thanks.

Dave
Click to expand...
Just read the specs. The thing is bound to convert a voltage up to 200mVdc
into a 3 1/2-digit LCD-display reading about 2-3 times/second. So whatever
the salesman claims, the thing is converting analog to digital. The specs
tell nothing about how it is done but why should you care as long as the
thing does what it's meant to do? Don't blame the salesman too much. He is
hired to sell, not to know much about the things he sells except for its
pricetags.

petrus bitbyter
 
On Tue, 1 Apr 2008 08:31:02 -0500, "Dave" <db5151@hotmail.com> wrote:

The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a voltage
meter that comes with some resistors used for setting it to the proper range
for whatever the user wants. And it only has two pins for input (I haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is it
likely that this does its job through the use of comparators, or some such,
and maybe it really doesn't contain an A/D converter chip? Or can I likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...
Click to expand...
---
The salesman is wrong, and I'd be willing to bet that the ADC in the
meter is an ICL7106 or one of the tens of millions of second-sourced
copies which have been sold since Intersil introduced the chip.

JF
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:nqk4v3tqkhfudtup4h4b2j5pmosv6a4vps@4ax.com...
On Tue, 1 Apr 2008 08:31:02 -0500, "Dave" <db5151@hotmail.com> wrote:

The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage
meter that comes with some resistors used for setting it to the proper
range
for whatever the user wants. And it only has two pins for input (I
haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is
it
likely that this does its job through the use of comparators, or some
such,
and maybe it really doesn't contain an A/D converter chip? Or can I
likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

---
The salesman is wrong, and I'd be willing to bet that the ADC in the
meter is an ICL7106 or one of the tens of millions of second-sourced
copies which have been sold since Intersil introduced the chip.

JF
Click to expand...
Hey John,

Found out the meter is a Velleman, and called there to speak with Scott, who
tells me it looks like it has a PIC chip, but that is covered with epoxy or
something, so that's out. It is actually made in Europe, he thinks. They
have an economy model which he sent me some info on, and it uses a 7107 (LED
display.) If nothing else, I could use that, even if I would rather have a
7106.

Thanks all for the input and feedback. Not sure yet exactly which path I am
going to take.

Regards,

Dave
 
Michael Black wrote:

<snip>

You can now get them for
ten dollars, which is the result of thirty years of volume and
displacement of analog meters.
Click to expand...
$2.99 at Harbor Freight, when they go on sale.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90899

On sale now. :)

Ed

Michael
Click to expand...
 
Michael Black wrote:
Thirty years ago I bought an Intersil evaluation kit for their just
released digital voltmeter IC, I guess it was the 7107. I paid fifty
dollars for it in Canada, and when built it made a nice panel meter.

That was a big step forward, it did allow for a DVM at a much lower
cost at the time. But it sure wasn't a CPU in there, it just better
integrated what had come before.

Even before that, there were multiple IC sets that went together
to make a DVM, the Intersil just moved forward a tad.

Now, they may use CPUs in there now if there is some good reason to
make it changeable by changing the code, but thirty years ago you
could get a DVM in a single IC. And that IC, or others like it,
are what's inside most DMMs, which is precisely why they got cheap.

I paid about eighty dollars for my first DMM in 1984, and that was
about as cheap as they came back then. You can now get them for
ten dollars, which is the result of thirty years of volume and
displacement of analog meters.
Click to expand...

You can buy a DMM at Harbor Freight for $2.95, when you catch them on
sale.


--
aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file
* drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

http://improve-usenet.org/index.html
 
On Tue, 01 Apr 2008 11:22:15 -0500, Dave wrote:
"John Fields" <jfields@austininstruments.com> wrote in message
news:nqk4v3tqkhfudtup4h4b2j5pmosv6a4vps@4ax.com...
On Tue, 1 Apr 2008 08:31:02 -0500, "Dave" <db5151@hotmail.com> wrote:

The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage
meter that comes with some resistors used for setting it to the proper
range
for whatever the user wants. And it only has two pins for input (I
haven't
actually seen it yet, so I am quoting what he told me.) *He* says it
doesn't contain an A/D converter, it's just a meter (?) My question: is
it
likely that this does its job through the use of comparators, or some
such,
and maybe it really doesn't contain an A/D converter chip? Or can I
likely
buy this, break into and modify it, and then use it as the readout for my
transistor tester, showing the gain of the device under test?

http://www.ace4parts.com/Products/PMLCD--LCD-PANEL-METER__PMLCD.aspx

Any thoughts are appreciated...

The salesman is wrong, and I'd be willing to bet that the ADC in the
meter is an ICL7106 or one of the tens of millions of second-sourced
copies which have been sold since Intersil introduced the chip.

Found out the meter is a Velleman, and called there to speak with Scott, who
tells me it looks like it has a PIC chip, but that is covered with epoxy or
something, so that's out. It is actually made in Europe, he thinks. They
have an economy model which he sent me some info on, and it uses a 7107 (LED
display.) If nothing else, I could use that, even if I would rather have a
7106.

Thanks all for the input and feedback. Not sure yet exactly which path I am
going to take.
Click to expand...
Another idea is that when you used such a technical term as "ADC", he
thought you meant a digital output, which it no doubt doesn't have.

Cheers!
Rich
 
"Dave the Dickhead "

The following link shows an LCD meter carried by my local parts depot. It
says "panel meter" and the sales associate tells me it is actually a
voltage meter that comes with some resistors used for setting it to the
proper range for whatever the user wants. And it only has two pins for
input (I haven't actually seen it yet, so I am quoting what he told me.)
*He* says it doesn't contain an A/D converter, it's just a meter (?) My
question: is it likely that this does its job through the use of
comparators, or some such, and maybe it really doesn't contain an A/D
converter chip?
Click to expand...

** It almost certainly uses a " dual slope integrating ADC "

http://www.analog.com/en/content/0,2886,760%255F788%255F94663,00.html

Around since the 1950s, available in IC form ( Intersil 7106/7 ) since the
mid 1970s.

Simply converts a DC voltage into a precise time interval, which is then
used to gate a counter on and off.

Voltages are not converted to binary numbers, so in a sense, it is more
analogue than digital.



...... Phil
 
"Bob Eld Retard "

It has to have an A/D converter to convert the 0 to 200mv analog input to
digital..
Click to expand...

** Yep - a " dual slope integrating ADC" .

http://www.analog.com/en/content/0,2886,760%255F788%255F94663,00.html

Most likely it is a single chip solution using a microprocessor
or some sort of custom array.
Click to expand...

** Bollocks.



....... Phil
 
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