INA826 evm

Nikolay Bozhilov

Prodigy 40 points

Other Parts Discussed in Thread: INA826EVM, OPA333

Hello,

sorry for my English it is not my first language.

I am new to electronics.

I have a problem regarding INA826EVM.

I am trying to build a circuit on the INA826EVM board (see attachment for a schematic).

I am using Rigel 333 as an input of the instrumentation amp.( http://www.rigelmedical.com/downloads/rigel%20333%20instruction%20manual.pdf)

I set up the Rigel to Sine waveform with 1 Hz amplitude of 1 mV.

I am setting the gain close to 1000 with a 51 ohm resistor.

I am using R3 and C1 to create a low pass filter to cut at 100 Hz.

I am using Opa333 for the DC offset. The Rigel has an offset.

R1 and R2 are used because the Rigel is floating.

I am expecting to measure about a 1 volt to the output with a scope.

This will help me to calibrate the the circuit thus, I will be able to measure low level ecg signals accurately.

My problem is that in this situation the gain is about 592 and if I change the the frequency to 10 Hz the gain changes as well.

I have basic knowledge to electronics, haven't worked with much opamps and never with an instrumentation amplifier.

Thank you for the support,

Nikolay

over 9 years ago

0 Pete%20Semig over 9 years ago

TI__Mastermind 25775 points

Hello Nikolay,

Please visit this link for more information concerning ECG signal acquisition. It has a few links to some useful information.

http://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/2437.ecg-heart-signal-acquisition.aspx

Try reducing your gain to 10V/V and ground the reference pin. Even though this will gain your electrode offset, the +/-9V should provide enough headroom to obtain an appropriate waveform. If that works, then try investigating your OPA333 circuit (at first glance it appears as though something is wrong with the supply...there is nothing referenced to ground).

I hope this helps!

0 Wei Xu41022 over 9 years ago in reply to Pete%20Semig

TI__Prodigy 140 points

Hello Nikolay,

You may need to increase C2 to be 1uF. The integrator is for the DC correction. It shouldn't affect your signal band.

regards,

Wei

0 Nikolay Bozhilov over 9 years ago in reply to Pete%20Semig

Prodigy 40 points

Hello Pete,

thank you for the information.

I have noticed that something may be wrong,

I will investigate.

Furthermore I got a feedback from a colleague of mine regarding the Rigel.

Thank you for the reply, I will test that.

Best regards,

Nikolay

0 Nikolay Bozhilov over 9 years ago in reply to Wei Xu41022

Prodigy 40 points

Hello Wei,

thank you for that.

I will test this out.

Best regards,

Nikolay

0 Nikolay Bozhilov over 9 years ago in reply to Nikolay Bozhilov

Prodigy 40 points

Hello,

I have found what was wrong with my circuit.

The Rigel 333 was not calibrated, that was why I did not have proper measurements.

Thank you for your help.

Nikolay

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