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" <[email protected]> To: "Jeremy Nichols" <[email protected]>, "Volt-Nuts" <[email protected]> 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) _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
