Input signal issue for a AD7606 + Arduino DUE + Load Cell DAQ

Hi,

I’m making a Data Acquisition System for force impact usign an AD7606 from Analog Devices, an Arduino DUE and a load cell. I already tested it following this guide an making the proper changes for Arduino DUE and some potentiometers for simulating the input signals. I can read variable 1-5 V signals pretty good but when I tried to read mV signals from my load cell I can’t see any changes in the Visuino Scope. I’ve read some forums and using an amplifier is recommended. However, when I read the AD7606 datasheet it says that since it has a High Analog Input Impedance, an amplifier isn’t needed. Also, I want to avoid the noise from the external amplifiers.

I also tested my load cell using the HX711 ADC and it works fine, but I can’t use it for my application because of its limited sampling frequency (80 Hz). AD7606 can give up to 200 kilo samples per second.

Does any one knows if I’m missing something for my input signal? if an amplifier is really nedded can you recommend me one?

Thanks

IMP1.JPG

You always need to amplify load-cell signals as they are super-small, this is nothing to do with impedance.

Typical gains used are around 1000, which means standard instrumentation amplifiers will have
low bandwidth, as trying to get 1000-fold gain in one stage is losing 99.9% of your unity-gain bandwidth.

A special multi-stage instrumentation amp circuit is needed to get huge gain, good CMRR and high
bandwidth. The easiest approach is to use a standard instrumentation amp set to a gain of 30 or so,
followed by a simple opamp gain stage of x30 gain.

What is the full scale output of the load cell (in mV) and what voltage are you using to power the load cell?