OP AMP with gain of 2000?

[steinless]

The load is a high impedance analogue input unit for some PLC.

When i say grounded my load, i connected both the lower end of the load and pin 5 both together with ground. When i do so, the readings fall to zero. Thats with a resistor to simulate the load. Have not tried with the load before.

For the capacitor, i used the largest value i could find...im going to try a lower value to see.

Th gain is fine i think i initally thought i need a larger value for the I/O to sense. But it seems to be alright. So i only need to stablise it.

The scopes ground? I never conected anything to it. For the voltage part, i got the idea from one of the samples. Pic 2. Arent they using like 3v for reference?

What i have now is PIC 1(the uglier one).

 

[Roff]

How did you measure the output in order to get the odd half-wave waveform? you obviously used a scope. Where did you connect scope GND?
Just because pins on different ICs have the same name (Ref), it does not mean you should connect them together.
Pic 2 is using a non-zero volt reference on the AD620 because they have used GND as the negative supply for the AD620, and its output will not swing to GND, so they shifted it and the A/D low-side reference positive with the voltage divider.
You have bipolar supplies, so you can use GND for the AD620 reference and for the A/D low-side reference. The A/D high-side reference can be whatever positive voltage you choose that is within the specified A/D range, but you must somehow protect the A/D from overvoltage from the AD620.

 

[Optikon]

The load is a high impedance analogue input unit for some PLC.

When i say grounded my load, i connected both the lower end of the load and pin 5 both together with ground. When i do so, the readings fall to zero. Thats with a resistor to simulate the load. Have not tried with the load before.

For the capacitor, i used the largest value i could find...im going to try a lower value to see.

Th gain is fine i think i initally thought i need a larger value for the I/O to sense. But it seems to be alright. So i only need to stablise it.

The scopes ground? I never conected anything to it. For the voltage part, i got the idea from one of the samples. Pic 2. Arent they using like 3v for reference?

What i have now is PIC 1(the uglier one).

If you have it connected as shown in the uglier picture, you need to tie the ref point (on both converter and ad620) to a low impedance point like power supply ground. That is if your A/d is not driving the reference (some have ref out pins) but I suspect it is an input. The diagram as-is looks like REF (on both parts) is floating.

 

[Optikon]

Not to throw too much into the pot at once, but you aren't still trying to get a gain of 2000 out of that first stage are you?