I am attempting to build an instrumentation amplifier circuit as part of a “home made EKG” project, but I am having a strange problem with the output of the circuit.
For the second time now, I have attempted to build a circuit and have tested it using a function generator at school. Using an oscilloscope, I find that a sine wave from the generator is in fact amplified according to the correct gain equations, thus suggesting the circuit is working correctly.
However, once I bring the circuit home to test the EKG portion, somehow the circuit no longer functions. Instead, I have connected it to a function generator and only receive a constant, unvarying high voltage output line on an oscilloscope. I have tried pressing down the IC op-amp chip I am using, an LM324, to no avail; I have even varied the voltage supply, although I am using the exact same supply (9v to 15 v battery eliminator) used at school when the circuit functions. I would appreciate some help, as I am getting somewhat frustrated - I have built several such circuits, even swapping out different ICs, and tested them at school only to find that the circuit no longe works at home.
Some ideas: as I am using a different function generator at home, could this one somehow be shorting/breaking the IC chip?
Could surrounding computers or other electronic devices be creating noise? I have tried turning off power supply strips to the devices to no avail.