Instructables

Voltage follower for the INA125?

I need to use a voltage follower that runs off a 9 v battery (actually, two batteries so +- 9V is available), from the output of a Burr-Brown INA125 amplifier to the analog input of a DATAQ data acquisition unit. The DATAQ is running at about 1000 data points per second.  Is there a particular op-amp that would be useful in such an application?  Or would something besides an op amp be more useful?  Thanks!

Why do you need the follower ? The output impedance of a follower is as close to zero as makes no odds, and the output of the INA 125 should be likewise, so what's the follower for ?
Prfesser (author)  steveastrouk4 years ago
...output of the INA125 should be...

As it turns out, "should be" does not mean "is". Therein lies the problem.
What circuit are you using around the 125 ? What's the error you're seeing in the rest of the system ? Channel cross talk or what ? I'm leery of adding noise from another amp, if its not necessary.

If, for whatever reason (like what load does your DAQ present???), you have to add a buffer, you may as well use a INA 105 as a unity gain buffer. You can't go wrong with Burr-Brown, but whatever, you are injecting uncertainty, if not noise.

Steve
Prfesser (author)  steveastrouk4 years ago
The circuit is pretty much lifted from the INA125 data sheet.  The input is a load cell from Aerocon:
    http://aeroconsystems.com/cart/products/20_50_100_kG_Load_Cell-20-64.htm

Used two 9v batteries in series to get +-9v.

The output of the INA125 goes to a DATAQ DI-158U (USB to computer).  Although I'm using the 5v reference of the INA125, the maximum signal at the DATAQ is about +-2.8 volts.  My thought is that I should get something close to +-5 V.

Of course I may be fulla sh*t, it wouldn't be the first time. :-)

Thanks!
What gain setting resistor did you use ?

S