ISOLATION FOR SIGNAL AMPLIFIER

Thread Starter

viju

Joined Sep 28, 2008
120
How to isolate the signal amplifier i.e from the sensor to the measuring circuit? I found in the internet ISO 122, ISO 124 solve this purpose.

How to connect this isolation amplifier? Do I need to connect at the amplifier input or at the output of amplifier?
 

t_n_k

Joined Mar 6, 2009
5,448
I have used the ISO 122 - works fine.

The only problem is that you need two power supplies - one isolated.

I used a small isolated (1W) DC-DC dual output (+/- 15V) converter module for the isolated side DC supply. They aren't cheap!
 

Thread Starter

viju

Joined Sep 28, 2008
120
I have decided to use two power supplies.But how to interface? I have decided to use this IC for gain amplifier ( 1:100). Should I have to feed signal into the IC or output of the amplifier to be connected to the IC?
Pls guide.
 

t_n_k

Joined Mar 6, 2009
5,448
The ISO122 has unity gain so if you require 100x gain you need to decide on which side of the isolation barrier you want to do the amplification.

If you have a very low input signal which is subject to noise &/or sitting at an unusual common mode level, you might consider running a differential input stage with the 100x gain before going to isolation. You can use your isolated power source to run this as well.

See this link for a typical diff amp.

http://focus.ti.com/lit/ds/symlink/ina111.pdf

You can buy complete single power supply isolation modules with gain but they can get quite expensive.
 

Thread Starter

viju

Joined Sep 28, 2008
120
Thankyou very much for the information T N K.I have built the application and it's working fine.
 
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