Help with pH circuit

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cgw94

Joined Jun 11, 2020
41
Hi all,

I posted a similar question a little while ago here

I have since acquired all materials to make this circuit shown below. Full walk through http://www.66pacific.com/ph/simplest-ph.aspx
1601494926838.png

My circuit is exactly the same and I do not get a reading.

When I connected a single 9v battery instead of 2 i was able to get a constant 1.4 volts across the pins. I am using pins 1 2 3 4 5. I measure across pins 1 and 4.

Ive been troubleshooting all day today and i cant seem to figure out what i am doing wrong. I started a new thread because the old one was answered and it seems to have gone off on a tangent.

My end goal with this circuit is to have it light up an LED when Acid is detected.
 

drc_567

Joined Dec 29, 2008
885
... Not quite sure if this is relevant, but is the op-amp powered up before the input voltage is applied? ... Read something about how the op-amp could be damaged if voltage is applied at the input prior to the placement of DC power at the appropriate pins.
 
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