Noninverting op amp doesn't work on a highly resistive load

[yungman]

Did you use FR4 for the boards?

It's better to use teflon or other special material, technique using guard ring also common, BUT I actually cut groove around the critical junctions ( actually cut all the way through) on the pcb to avoid creepage. I have been using this technique for high impedance and high voltage isolation. There's similarity between the two, surface creepage is a very a important thing. This technique allow me to use cheaper material and not as critical in cleaning...I am born cheap,cheap is my middle name!

I used round can opamps at the time, I created footprints that had pins farther apart so I can cut groove around pin 2 ( this is standard pin out of opamps, 2 is -ve input, 3 is positive, 6 is output, 4 is -V, 7 is +V). I made the trace of the -ve input as short as possible as shown. I layout my own pcb, I don't want to hear complain from the pcb designers that it's too hard, too much trouble... From my experience with HV, high impedance and high speed RF, pcb layout is where you win or loss the war, I layout all my pcbs.

Some people use standoff for the -ve input of opamp too. I tend NOT to do that if I can help it. Cost money to custom assemble.

 

[Vitina]

I am seeing many attempts to help answer a question that is simply bait.

The circuit given was from the application data without substantial detail.

And how is the output being used,, a "rad" meter?, a programable electrostatic device at a few hundred volts?, a smoke detector than uses a nominal 100-1000meg ohms.

And there may be confusion as to where the load resistor is being used as in the comment on not seeing RL as needed, (from the ap data circuit).

Many tried to explain that sometimes simply taking the measurement disrupts the measurement. Did someone say...

[Post edited slightly by a Mentor after a PM discussion]