Possible malfunction of a quarter bridge amplifier

[Jimbo bob]

Hi dear enthusiasts ,

One of my friends very kindly made me a strain gauge bridge amplifier around 6 months ago. I had a little play with it and put it aside. I have attached a picture of the amplifier circuit. The circuit was used to amplify the output voltage of a quarter bridge. My friend’s instructions were to supply the amplifier circuit with 8V-12V (i.e. through Vin and Gnd). Then I should have a 5V excitation voltage (between V+ and V-) which I can supply to my quarter bridge. The output of the bridge in connected to S+ and S- terminals of the amplifier circuit. Then, an amplified output voltage can be measured between Gnd and Vout which should be between 0V to 5V.

Recently, I decided to test this circuit again, but I keep getting 5V from Vout using a digital multimeter.

I would really appreciate it if someone could guide me on how to troubleshoot this circuit and determine whether the outcome I am getting is expected or the circuit is faulty.

Many Many thanks in advanced

 

[Harald Kapp]

A circuit diagram would make it muuuuch easier to understand the circuit.
One possibility is that your amplifier has run into clipping due to too much offset.

 

[Jimbo bob]

A circuit diagram would make it muuuuch easier to understand the circuit.
One possibility is that your amplifier has run into clipping due to too much offset.

Thanks Harald. You are absolutely right about a circuit diagram making things quite easier. Unfortunately, I was not able to obtain such diagram for the time being. If the amplifier has run into clipping, then reducing the offset using the potentiometer on the circuit should possibly fix things up, correct? I will give it a try.

Thanks again