how to connect to get gain?

[chenjk09]

Hi everyone,

i used the AD624AZ in my ECG circuit and i have few questions to my circuit,
i go though the data sheet of it but i still have few things to ask like :

1- how to check the gain using multisim.
2- how to connect the to check the gain using multisim.
3- data sheet said that the gain to be 1000 can be set on pin's 13,12,3 and 12,16.

Attached file error I connect I think is wrong

I want to get the result of shown in attached file correct.

thanx in advance
Regard's

 

[audioguru]

You are not measuring the signal gain of a heatbeat that has out-of-phase signals on the inputs.
Instead you are measuring the common-mode rejection because you have the same signal phase on both inputs.
Your measurement is very good at about -140dB.

 

[chenjk09]

sorry i'm new to multisim.. i set different AC supply input and??

 

[audioguru]

Why are you feeding the same 120VAC into both inputs?? It is 120 times too much. The inputs might pickup 1V of common-mode mains hum if their shielding is poor.
A heartbeat is about 1mV (0.001V) with opposite phase on the inputs.

 

[chenjk09]

how should i connect to get the gain output shown in correct.jpg?
i not sure how is the conncetion is correct to check the gain.

 

[audioguru]

Why are you measuring the common-mode rejection instead of measuring the signal gain?

 

[chenjk09]

I want to measure the CMRR for Instrumentation Amplifier. The small ac signal voltage (less than 5 mV) detected by the sensor on the electrodes will be accompanied by a large ac common-mode component (up to 1.5 V) and a large variable dc component (300 mV). The common-mode rejection specified by the AAMI (Association for the Advancement of Medical Instrumentation) is 89 dB minimum for standard ECG and 60 dB minimum for ambulatory recorders. The CMRR of AD624 with gain of 1000 is shown on correct.jpg. The equation of the CMRR:

CMRR = differential gain / common mode gain = Adm/Acm


i not sure how to connect using Multisim 11.0
my error.jpg i know is wrong connection.

 

[audioguru]

Sorry, I am not a student and am not a teacher. I think they are the only people who use Multisim.