AD624 with ECG i need help plzzzz urgent

[wavestorm1986]

good day to all
i used the AD624AZ in my ECG circuit and i have few questions to my circuit means that i already got the results and i only need to understand more the idea of how AD624 is working, i go though the data sheet of it but i still have few things to ask like :

1- how much the gain of the circuit below.
2-it's 16 pins there are few pins is not connected why like this .
3- data sheet said that the gain can be set on pin's 13,12,11 !! why then using 3,11,13.
4- if i want to boost the signal more,i mean the voltage i have to use a pull up resistance so what's the best value for that.

i will post the result and and the simulation using multisim 10, any help will be THANKFUL

thanx in advance
Regard's

 

[nuclearrambo]

AD 624 is an instrumentation amplifier. you can read about it here Instrumentation amplifier - Wikipedia, the free encyclopedia
Probably a modification of basic difference amplifier.

EDIT: i am sorry i didnt read the ful post. Above text is totally useless. Sry.

 

[wavestorm1986]

nuclearrambo
thank u for the response
but i already read the data sheet and i pass by the link u post it. if u do not mind i just hope u can help me to know the list i post it

thanx in advance

 

[ericgibbs]

nuclearrambo
thank u for the response
but i already read the data sheet and i pass by the link u post it. if u do not mind i just hope u can help me to know the list i post it

thanx in advance

hi,
Pins 11,12, & 13 are for setting the FIXED gains as shown on the datasheet.
Pins 3 & 16 are for adding a fixed or variable resistor in order to further control the gain.

Pins 14 & 15 a for Nulling the amplifier, they are not used on this project.

EDIT:
Based on the data the gain is on full at 1000.

 

[nuclearrambo]

datasheet says that gain = (40k/Rg)+1 = (40000/225.3)+1 = 178.5.
i dont know if i am right. but thats what i was trying. i am not an expert, just trying to help.

 

[wavestorm1986]

hi,
Pins 11,12, & 13 are for setting the FIXED gains as shown on the datasheet.
Pins 3 & 16 are for adding a fixed or variable resistor in order to further control the gain.

Pins 14 & 15 a for Nulling the amplifier, they are not used on this project.

EDIT:
Based on the data the gain is on full at 1000.

thank u sir for your help
but after i go though the table in the data sheet and you post also, i found that the pin's are 3,11,13 which i couldn't find a match with what i want to find, and something else why there are a connections between 4,5 ??

Regard's

 

[wavestorm1986]

datasheet says that gain = (40k/Rg)+1 = (40000/225.3)+1 = 178.5.
i dont know if i am right. but thats what i was trying. i am not an expert, just trying to help.

thank you for yoyr help sir
how you know 225.3=Rg ???

Regard's

 

[nuclearrambo]

thank you for yoyr help sir
how you know 225.3=Rg ???

Regard's

i saw the block diagram of AD624 and the way you had connected those pins 13,12,11
I am not sure if i am correct, i could be.

 

[ericgibbs]

thank u sir for your help
but after i go though the table in the data sheet and you post also, i found that the pin's are 3,11,13 which i couldn't find a match with what i want to find, and something else why there are a connections between 4,5 ??

Regard's

hi,
The 10K on pins 4 & 5 is for nulling the inputs.

Pins 16,12 & 13,11 are linked to pin 3,,, Gain =1000

 

[ericgibbs]

hi,
To increase the amplitude of the signal you could add a non inverting OPA after the filter.

 

[nuclearrambo]

hi,
The 10K on pins 4 & 5 is for nulling the inputs.

Pins 16,12 & 13,11 are linked to pin 3,,, Gain =1000

that was helpful for me as well in learning handling of such amplifiers.

 

[wavestorm1986]

thank you guy's so much for your help
but i few things like the CMRR which is have fixed value which is 130dB min, so is it means that i can find the value of CMRR with respect to gain=1000 ?? coz i read the data sheet and i did not find a way to do any math to find CMRR !!


thank you again

Regard's

 

[ericgibbs]

thank you guy's so much for your help
but i few things like the CMRR which is have fixed value which is 130dB min, so is it means that i can find the value of CMRR with respect to gain=1000 ?? coz i read the data sheet and i did not find a way to do any math to find CMRR !!


thank you again

Regard's

hi,
The CMRR of 130db applies to gains of 500 to 1000.

If you want to increase the gain to greater than 1000 then

Connect a resistor from pins 3 and 16 [disconnect the others 13,12,11 & 10.]

The resistor value is Rg = 40k/[G-1] , where G= the gain you want up to a maximum of 10,000 times.

 

[wavestorm1986]

ok thank you sir
R1=R2= 47k will limit the current from the source to the IC correct ?
the capacitors that connected to the +9,-9 is to smooth out the voltage source to get better signal correct ??

Regard's

 

[ericgibbs]

ok thank you sir
R1=R2= 47k will limit the current from the source to the IC correct ?
the capacitors that connected to the +9,-9 is to smooth out the voltage source to get better signal correct ??

Regard's

hi,
The 47K's will help prevent damage due electrostatic discharge by limiting the current flowing in the input pins.

The decoupling capacitors on the power pins are to reduce any electrical noise thats present on the power rails.

 

[wavestorm1986]

ok thank you sir very much

anything else will come and check

Regard's

 

[chenjk09]

multisim

hi,
what is the input device for the ECG using multisim?
hope someone can help

thanks

 

[ericgibbs]

hi,
what is the input device for the ECG using multisim?
hope someone can help

thanks

hi,
Ref your PM.
Sorry, I do not use Multisim,, I use LTspice simulator...

 

[chenjk09]

LTspice simulator

Hi,

for LTspice simulator what is the input device use for input for ecg?
i will try seach on it

thanks

 

[ericgibbs]

Hi,

for LTspice simulator what is the input device use for input for ecg?
i will try seach on it

thanks

hi,
Look at this link, download suitable audio wav files.
https://www.soundjay.com/heartbeat-sound-effect.html

Then in LTspice use wavefile=C:\filename.wav chan=0 with a Independent Voltage source model.

You can then use the audio file to input heartbeat sounds into your simulation.