bigal_scorpio
Active Member
Hi to all,
I have just made a voltmeter from this site ICL7107 / ICL7106 - Digital Voltmeter
It is working ok in a fashion, but seems to be varying in its measured results when compared to both my DMMs.
I have changed the input resistor to 10k to give 2v scale as this is all I will be measuring but low end measurements tend to be small and the upper end towards 2v seem to be too high!
The author says to adjust the voltage between pins 35 and 36 on th 7107 to 1v but when I do the readings on the display are vastly wrong, over double those from my DMMs.
If I adjust the pot to measure a battery say 1.544v to agree with both my DMMs then the readings from a dead battery say .734v on my DMMs would show as .453v on the 7107s display.
I have used 1% resistors throughout and good spec caps. Is there some likely cause to this problem that I should be looking for or are the 7107s that innacurate (seems unlikely)?
Any ideas guys?
Thanks Al
I have just made a voltmeter from this site ICL7107 / ICL7106 - Digital Voltmeter
It is working ok in a fashion, but seems to be varying in its measured results when compared to both my DMMs.
I have changed the input resistor to 10k to give 2v scale as this is all I will be measuring but low end measurements tend to be small and the upper end towards 2v seem to be too high!
The author says to adjust the voltage between pins 35 and 36 on th 7107 to 1v but when I do the readings on the display are vastly wrong, over double those from my DMMs.
If I adjust the pot to measure a battery say 1.544v to agree with both my DMMs then the readings from a dead battery say .734v on my DMMs would show as .453v on the 7107s display.
I have used 1% resistors throughout and good spec caps. Is there some likely cause to this problem that I should be looking for or are the 7107s that innacurate (seems unlikely)?
Any ideas guys?
Thanks Al