Piezoelectric Sensor with DAQ

[Nitsan]

Hi all!

can I connect this PE sensor to a NI-9232?

http://pdf.directindustry.com/pdf/meggitt-sensing-systems-measurement-group/endevco-r-model-7240c-mi...

There isn't a lot of info there... what worries me is the use of pC/g instead of mV/g.

any thoughts?

Thanks

[johnsold · Accepted solution]

A piezoelectric sensor with charge output requires a signal conditioning circuit to convert that charge to a voltage. While, in principle, a capacitor will do the job, in practice very careful circuit design may be required to get accurate results. 

The NI 9232 is designed to work with IEPE sensors, which have built-in signal conditioning.  If you dig deeply enough into the specifiactions you find the input impedance is 324000 ohms, which is much too low to work directly with a piezo sensor.

You need a signal conditioner.  The datasheet you linked lists signal conditiners among the acccessories.

Lynn

[Henrik_Volkers · Accepted solution]

If you already have the sensor and the DAQ you can look for a inline IEPE signal conditioner like this one.

Or you buy a charge amplifier. If you think of building one here is one I build 😄 . Depending on what you need, it's not only the circuit, it's HOW you build it and WHAT components you use.

PTFE standoffs, a very low leakage, stable feedback capacitor, low bias current, low noise, high GBW OP, intensive cleaning of the PCB and burn in..... just to name some points.   A pC is not that much electrons and they get lost easely ;).

[Nitsan]

Thanks guys! You've been very helpful!