You cannot measure "a couple of volts" with this circuit; it is designed=20
for +/-200mV fullscale.  It 'probably' won't damage it to try it as=20
there is a 1Meg input resistor.  But at anything it thinks is over=20
200mV, it will display + or - 1 with the other digits blank. Your=20
circuit will probably show this even if it is working properly if you=20
leave the input floating.

To trouble shoot further, get a good datasheet such as the one from=20
Intersil. Maxim's is a photo-copy and sux.  Then go to Intersil's=20
website and get some of the ap-notes on using it. In particular, get=20
from this page:
http://www.intersil.com/content/intersil/en/products/other-analog/special-a=
nalog/integrating-display-output-a-d-converters/ICL7107.html

this document:
http://www.intersil.com/content/dam/Intersil/documents/an05/an052.pdf

which shows a wealth of trouble shooting and debugging info. Read it=20
carefully.

And remember - your circuit will do what you indicate that it's doing=20
for input voltages over 200mV.


On 5/4/2014 5:55 PM, Richard R. Pope wrote:
> Don, Robert,
>       I put a 1M resistor across the IN LOW and IN HIGH connections. When
> I first hook up power the display comes up showing 1333 and then it
> clears and shows -1, the other digits are blank, and. the - sign is
> flashing. The reference voltage is set at exactly 100mV. If I try to
> measure 100 mV the - sign stops flashing. When I try to measure a couple
> of volts the minus sign goes out. I have tried 3 different chips. I have
> gone over my connections and the wiring more times than I can count. I
> am so frustrated. Any ideas? Here is the link again:
> http://www.electronics-circuits.com/tech/wp-content/uploads/2012/10/del20=
009.png
> I'm not using the circuitry on the left with the individual LEDs. Please
> help?
> Thanks,
> rich!

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.