Please see the attachment for my circuit.I have 2 74cn op amp, a signal generator, a dc power supply.
Now I want to measure the voltage across the 2 resistors R with 2 differential amplifier.
I measure voltages and make my ref point to be 'com' in the dc power supply. and I connect 'com' and 'gnd' together.
I wonder if the 2 amplifiers can work well.Because the inverting input signal of the upper amplifier is the non-inverting input of the lower amplifier.
If so, how can i resolve this problem?
I work it on a breadboard but have not tested it yet

 

There is nothing wrong with having two op amps on the same breadboard. The 741 op amp is usually characterized at supply voltages of +/- 15V.

 

That circuit looks like it will work if you feed the amplifiers with the right voltage and keep the gain low enough to avoid clipping of the outputs.

 

thanks for the reply!!
What do u mean by keeping the gain low enough to avoid clipping ?
I set the gain to be 100 with R1=R2=1k;Rf=100k

 

That circuit looks like it will work if you feed the amplifiers with the right voltage and keep the gain low enough to avoid clipping of the outputs.

What do u mean by keeping the gain low enough to avoid clipping ?
I set the gain to be 100 with R1=R2=1k;Rf=100k

 

If the voltage across the resistors on the left is 5 volts and the gain is 100, then the amplifiers will try to output 500 volts. This is impossible because they can not survive a power supply of 500 volts. This will cause clipping of the wave on the output of the amplifiers.