AnsweredAssumed Answered

AD8227 as tenso AC bridge amplifier - overshoot problem

Question asked by Wojtek85 on Apr 11, 2016

Dear Analog Devices,

I have a question about AD8227 as amplifier used in AC-excited tenso bridge. I'm using AC square wave excited full bridge. Exciting signal comes from 3V switching by analog switch (signal is bipolar). Signal which control switching comes from ADA2200 (synchronous demodulator). Switching frequency is about 7kHz. The problem is that signal amplified by AD8227 (diagonal of the bridge) has large overshoot at the edges. I'm not quite sure if it is a settling time which for AD8227 is (depending on gain, I have about 10V/V gain) about 15us or it is caused by something else... What would you suggest to do - change InAmp AD8227 to faster one or there is some possibility to overcome this effect. I'm afraid it will prevent proper demodulation process.

I attached photo from scope. It is amplified inbalanced signal comes from unloaded strain gauge. There are really big overshoots. Amplifier gain is about 10V/V. AD8227 common mode voltage for IN+ and IN- is 1.5V. InAmp is powered from 3V REF193.

 

Best regards,

Wojciech

Zdjęcie2318.jpg

Outcomes