Hello everyone.

I'm working on a project for automatic vegetable growing system and designing a PCB for a device that will have the possibility to measure pH probe readings of water using AD795 operational amplifier.
The thing I'm confused about is the output of the AD759 - the supply voltage is +15 and -15 volts and in the datasheet it sais that the op amp outputs 1V/pH unit. Does this mean I can trust the datasheet and the output is positive voltage in the range of 0-14 volts? I plan to use a voltage divider and then feed the output to an ADC.

Would appreciate any help. I'm not too good at analog electronics and this is the part that is keeping me stuck.

 

Yes if you input a positive voltage from ground at pin3 +input , you get a positive voltage out, maximum supply is 36V (+/-18v).

 

The circuit will output 0 V at pH of 7 with a standard combination probe. The gain is incorrect for a standard probe and the sign of the slope is wrong (probe output is about -59 mV/pH at 25 °C relative to pH 7; i.e. at pH 0 the output is about +400 mV and at pH 14 it is about -400 mV).

I have only skimmed it, but Texas Instruments AN-1852 Designing With pH Electrodes looks like it should be helpful.

 

Thanks for the input guys. I'll take a look at the Texas Instruments guide and later let you know of how it went.