Hi guys i need you help
Im trying to build an EMG circuit which amplifies the electrical signals obtained from muscles to an output voltage that can be of easy operation with microcontrollers.
Im using a INA114 instrumentation amplifier and lf351 opamps along with the required R and C to be used as a high pass and low pass filter.
Ive tried it once it was working, but after that it stopped working. I always get some arbitrary values and wasnt been able to fix this problem.
I tried powering the In-amp via single supply as well as dual supply;nothing works.
IVE ATTACHED the exact circuit diagram ive used in my project.(in the attachment the input and the gain resistor has been put wrong, but i corrected it in my circuit)
So to start debugging i was checking the out put of the In-amp, regardless of the input the output is showing a constant 1.18V. Im not able to find any solution to this. Can you please help

 

hi,
As it was once working, have you tried a new INA114.?
Its possible you have blown the IA, I dont see any ESD limiting resistors on the inputs,

E

 

i was just wondering that as everything was calculated, and the input also was under normal range, why will the IA get ruined? If ESD was the case can you guide me to the proper resistor values to prevent electrostatic discharge(esd) as EMG signals are very small (0-10mV)

and another thing is my circuit correct?

 

hi,
Check the pin connections, you are showing pin #8 as -V, it should be pin #4.
Also please mark the 'other' pins on your circuit diagram.
E

 

what i actually put in my circuit blueprint, has been rectified in the circuit that i have actually used of all pin connection errors. There is no error on that part i can assure u that. please tell me more on how to prevent ESD. i think that is causing all the problem.

 

hi a,
Look at this clip from a IA d/s.

E