Voltage Source (IEPE) sensor interface to MCU

[ali_asadzadeh]

Hi,
I just wanted to know how to power and interface these kinds of sensors to my MCU ADC, for example AC102-1A sensor,https://www.ctconline.com/fileup/3DNEWPDF/AC102series_datasheet_3D.pdf
 how should I power the sensor and read it's data
any suggestions are welcome.

[ajb]

From their website: https://www.ctconline.com/FileUp/PrdDS2011/5_TI_PwrRequirements_DS.pdf

CTC sensors will function well with a constant current power unit, which provides 2-10 mA with
a DC voltage level between 18 and 30 VDC. We recommend using a current source of 2 mA and
24 VDC. This can be provided by using a data collector or by an interface circuit.

Please note: The cable should be shielded and grounded at the interface end for optimum
rejection of external noise. All CTC sensors have an internal shield that is connected to the
negative terminal. CTC accelerometer cases are isolated from the circuitry for optimum noise
rejection. Each sensor will transmit a signal riding on their specified bias voltage. This is typically
+/- 5 volts riding on a 12 volt bias (please refer to the data sheet for each particular sensor).

So provide it with a 2mA current, and you'll get a ~12V+/-5V signal out of it.  You can either offset the output or AC couple it to get it into a range that your MCU's ADC can handle.  You'll need to attenuate it as well, which can be a simple voltage divider.

[ali_asadzadeh]

Thanks for your help,there is another question, can I replace the CR220 with a LM317 in constant current mode?

[ajb]

Maybe, the LM317 isn't specified for output<10mA.  It might not behave very well at currents below that. There are several other constant current source topologies you could use. 

[ali_asadzadeh]

Thanks, Do you recommend any cheap one?

[ConKbot]

The current source needs to faster than your gauges signal by a significant amount so its current output remains high impedance, otherwise it it can start to distort your signal. With the resonance of those gauges at 23khz, you can assume signal up to that (though don't try and measure something near resonance, best case it will read way higher than actual, worst case it breaks the gauge) 
An lm317 starts to run out of steam in the 10-100khz range (output impedance rises for a voltage output, drops for a current output)   But a zener/pnp current source, or jfet or depletion mode mosfet current source will have plenty of bandwidth for this.

[ali_asadzadeh]

Thanks