I’m testing batteries at a battery storage construction site with a Fluke 87V looking for 50.5 VDC (~0.01%). I’m looking for a solution that produces audible indication so I don’t have to look a the DMM each time I probe for verification. TIA
Thanks to everyone for their thoughts on this and I will read all your replies just as soon as I correct my typo that should have read 0.1% tolerance and for all practical matters it could go be 0.2% and still work for what I’m doing. I apologize folksWelcome to AAC!
That's a tall order. 0.01% is an extremely tight specification. Are you sure you really need it that accurate? Even the Fluke87's rated accuracy is 'only' 0.05%. on its DC setting.
I think all components in any designed measuring circuit would need individual tolerances even tighter than 0.01%, or the calibration of the overall system would need a similar accuracy, and the whole measuring set-up would need to be accurately temperature-controlled and electromagnetically screened. So the sourcing of suitable components is going to be a challenge and the system cost could be high. What is your budget for this?
Now that’s funny. Not just because it’s funny but because it’s got the additional Gary Larson sting that it would work for me. Aaaarrrgghh. I knew this was coming when I got in here.Look up "talking voltmeter for the blind".
But to get 0.01% accuracy, you would likely need a precision bench multimeter, not a hand-held one.
However I think that degree of accuracy is much higher than you need to measure battery voltages.
True, but the spec has changed ...Even with 10 turns post it will be hard to set to within 0.01%.
That is a range of +/-1 in 500, or +/-0.2%. I know that's not the same as the setpoint accuracy he mentions, but it does give a starting point for the two trip points. Because he accepts the idea of using the voltmeter to calibrate the comparators (as opposed to the comparator circuits being inherently accurate), the only real issue is stability. If the temperature coefficients of the trip points voltage divider string are tightly matched, then the problem reduces toOops not to beep at <50.4 or >50.6
Oh, I see.but the spec has changed ...