Voltmeter not liner

[House91320]

i have this curcet http://www.eleccircuit.com/icl7107-icl7106-digital-voltmeter/ and the voltage is fine at one end but way out on the other. for exampel an imput of 1 volt is corect on the meter but an imput of 19 is off by 10.

[bilko]

I assume that you are using the 1M ohm input resistor

From the details posted on the website ...

The voltmeter can also be configured to measure different voltage ranges and display higher voltage resolution. Replacing 1M with 100K resistor will allow to measure 0 – 19.99V voltages with 0.01V (10mV) accuracy.

[House91320]

i should have mentioned i am using the 100k

[bilko]

What do you get when you measure between pin 36 and ground ?

[House91320]

2 its suppose to be one isnt it

[bilko]

Yes according to the docs

[House91320]

i am looking at the docs and it says a differences of 1v between 35 and 36

[qno]

Note that the 7107 has a differential input.
Both inputs need to be between 1.5 and VCC-1V.

In short you can not use this chip when the powersupply and the measurement ground are the same.
Use a floating power supply.

[bilko]

In short you can not use this chip when the powersupply and the measurement ground are the same.
Use a floating power supply.

It is OK to use this chip in single ended mode, tie pin 30 (in Lo) to ground. Check Intersil application notes Fig 12.