Panel Meter for Negative Voltage
Does anyone know of an available 3-1/2 to 5 digit inexpensive LED panel
meter of the type offered by many eBay sellers that will read negative
voltage? Or, both negative and positive voltage? I have +5 to +12 vdc
available to power the meter but I need it to display negative voltage.
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
All of the cheap 3-digit panel meters I’ve purchased have the ability to
read/display positive and negative voltages.
On Mon, Sep 7, 2020 at 12:12 PM Larry McDavid lmcdavid@lmceng.com wrote:
Does anyone know of an available 3-1/2 to 5 digit inexpensive LED panel
meter of the type offered by many eBay sellers that will read negative
voltage? Or, both negative and positive voltage? I have +5 to +12 vdc
available to power the meter but I need it to display negative voltage.
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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--
Jeremy Nichols
Sent from my iPad 6.
That is not my experience. I bought several kinds on eBay after
inquiring and being assured by the seller that the meter would measure
and display a negative voltage, only to find on receipt that the meter,
powered from +5 vdc, displays zero, close to zero or a nonsensical value
when the sense lead is connected to a voltage negative with respect to
the return for the meter power.
And, on close inspection, the display has no LED segment to indicate a
negative voltage.
The other dirty little secret about these cheap meters is that their
response or settling time can be two seconds!
Has anyone actually got such an inexpensive panel meter that measures,
displays the negative voltage and indicates that the voltage is
negative? If so, please refer me to the sales listing.
Larry
On 9/7/2020 12:53 PM, Jeremy Nichols wrote:
All of the cheap 3-digit panel meters I’ve purchased have the ability to
read/display positive and negative voltages.
...
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
There are (at least) a couple different kind: two-lead meters and
three-lead meters. The two-lead kind use the same voltage for power as the
voltage they’re measuring. They can measure only positive voltages above
some minimum amount.
I checked one of my three-lead meters measuring a 10-Volt Standard. It uses
a power supply voltage between 3.5 and 30 Volts and can measure 0.000 to
33.000 Volts. I guess it therefore can be called a 5-digit Voltmeter.
However, it cannot measure negative Volts so I was wrong. My apologies! I
would post a photograph but can’t find a reference to whether that is
allowed.
On Mon, Sep 7, 2020 at 1:46 PM Larry McDavid lmcdavid@lmceng.com wrote:
That is not my experience. I bought several kinds on eBay after
inquiring and being assured by the seller that the meter would measure
and display a negative voltage, only to find on receipt that the meter,
powered from +5 vdc, displays zero, close to zero or a nonsensical value
when the sense lead is connected to a voltage negative with respect to
the return for the meter power.
And, on close inspection, the display has no LED segment to indicate a
negative voltage.
The other dirty little secret about these cheap meters is that their
response or settling time can be two seconds!
Has anyone actually got such an inexpensive panel meter that measures,
displays the negative voltage and indicates that the voltage is
negative? If so, please refer me to the sales listing.
Larry
On 9/7/2020 12:53 PM, Jeremy Nichols wrote:
All of the cheap 3-digit panel meters I’ve purchased have the ability to
read/display positive and negative voltages.
...
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
--
Jeremy Nichols
Sent from my iPad 6.
Larry,
Circuit Specialists has several 3-1/2 digit panel meter models that will satisfy your need. They have both LED display models and LCD display models. Examples are:
LED models:
[ https://www.circuitspecialists.com/digital-panel-meter-cx102a.html | https://www.circuitspecialists.com/digital-panel-meter-cx102a.html ]
https://www.circuitspecialists.com/digital-panel-meter-pm-1029a.html
LCD models:
https://www.circuitspecialists.com/lcd-panel-meter-pm-128a.html
https://www.circuitspecialists.com/lcd-panel-meter-pm-138.html
https://www.circuitspecialists.com/lcd-panel-meter-pm-1028a.html
eBay and AliExpress have similar meters; look for those that use separate power supply wires They usually specify a 9V power source for operation, but there aree models (a bit more expensive) that can use a 5V power source. These have a negative voltage generator circuit .built into the meter for teh A/D converter. See the datasheet for the ICL7106/ICL7107 A/;D Converter for details [ https://datasheets.maximintegrated.com/en/ds/ICL7106-ICL7107.pdf | https://datasheets.maximintegrated.com/en/ds/ICL7106-ICL7107.pdf ] .
You're wondering about LED models that don't seem to have a minus sign on the display; since the most significant digit on a 3-1/2 digit meter can only display a "1" digit or a blanked digit, the middle segment is used for the minus sign. This method eliminates the need for a special +/- sign LED digit.. LCD models have the minus sign on the display.
Cheers,
Dave M
From: "Larry McDavid" lmcdavid@lmceng.com
To: "Jeremy Nichols" jn6wfo@gmail.com, "Volt-Nuts" volt-nuts@lists.febo.com
Sent: Monday, September 7, 2020 3:46:59 PM
Subject: Re: [volt-nuts] Panel Meter for Negative Voltage
That is not my experience. I bought several kinds on eBay after
inquiring and being assured by the seller that the meter would measure
and display a negative voltage, only to find on receipt that the meter,
powered from +5 vdc, displays zero, close to zero or a nonsensical value
when the sense lead is connected to a voltage negative with respect to
the return for the meter power.
And, on close inspection, the display has no LED segment to indicate a
negative voltage.
The other dirty little secret about these cheap meters is that their
response or settling time can be two seconds!
Has anyone actually got such an inexpensive panel meter that measures,
displays the negative voltage and indicates that the voltage is
negative? If so, please refer me to the sales listing.
Larry
On 9/7/2020 12:53 PM, Jeremy Nichols wrote:
All of the cheap 3-digit panel meters I’ve purchased have the ability to
read/display positive and negative voltages.
...
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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