For the 1528-4403-ND panel meter, what is the DC input impedance and what are the size and locations of the holes required for mounting it?
Thank you for your inquiry.
I checked Adafruit’s website, I don’t see any further information there available for this meter.
As they’re a community driven educational supplier, you’d be encouraged to ask Adafruit for further details for this product on their forum located here
Thank you but “been there and done that.” I was hoping that you, as a bigger purchaser, might have more leverage.
Since the analog meter market ended up on life support a couple decades ago it’s gotten very hard to even find most meters and a center zero voltmeter is like hen’s teeth.
If this was for a one off project then I’d buy it and determine the impedance using a resistance decade connected in parallel.
If this was for one of my employers products, we’d never consider a part from Adafruit since it can disappear from the market at any moment. Instead we’d go to our normal supplier, Hoyt Electrical Instrument Works. https://www.hoytmeter.com/
I’d expect to pay about 10X the Adafruit price if we ordered 100 pieces.
These are the measurements (in inches) that I made on one of these meters with my calipers.
My Fluke DMM says the DC input resistance is approximately 30k ohms and that agrees with some voltage/current measurements that I made into the meter.
1Kohm/V = 1mA FS, a common mA FS value, sounds good for a low cost voltmeter, higher end ones are 20Kohm/V = 0.05mA/50uA FS.
From its (center/idle) zero current/voltage position to its full current/voltage position, this meter only spans 15 volts so 15v/30k = 0.5mA FS and that is indeed what I measured while pushing +15v at it. The polarity of the current and the swing of the meter changed when -15v was instead pushed at it, but the current still topped at 0.5mA.
The +/- get combined in traditional meter specification terminology because everything is based on full scale (FS). It’s 0.5ma HS (half scale).