Static Force Signal from Dynamic Piezoelectric Sensor

[zuegesim]

I have a Kistler triaxial piezoelectric force sensor 9017C with the Kistler Charge amplifier 5073A. I connected the three channels from its D-Sub 15 pole with an NI 9209 D-SUB Module (differential style), which in turn is in a NI cDAQ-9174. I would like to read the static forces from the sensor. However, when acquiring the Data with the DAQ Assistant using Voltage Input, it appears it only outputs the dynamic force / change in forces, not the static force. Also, in the DAQ Assistant, when I select the IEPE, it does not find any applicable appliances/channels. What do I need to do to get the static forces?

Also, I have the 2019 Labview Version.

[GerdW]

Hi zugesim,

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@zuegesim wrote:

I have a Kistler triaxial piezoelectric force sensor 9017C with …

I would like to read the static forces from the sensor. 

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You know the main application for piezoelectric sensors?

[zuegesim]

Hi GerdW

Due to budget reasons this is the sensor I have to work with. Also, my measurements are more quasi-static than truly static, so it should still be possible, right?

Cheers

zuegesim

[GerdW]

Hi zuegesim,

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@zuegesim wrote:

Due to budget reasons this is the sensor I have to work with.

Also, my measurements are more quasi-static than truly static, so it should still be possible, right?

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Piezoelectric sensors typically only react on dynamic changes, for static input their output is zero. How do you want to measure static values then?

You might start with integration of your measurement data, but

• you need a known start value
• you will still run into accuracy problems quickly

[Henrik_Volkers]

Your sensor together with the kistler charge amplifier should be able to measure quasi static forces.

The charge amplifier should be set to  long time constant, and before you start the measurement you need to activate the amplifier measure mode.

Copy from 5073 datasheet:

Principle of Operation of Charge Amplifier
The charge amplifier converts the charge generated by the
sensor into a proportional low-impedance voltage signal. The
amplifier always measures an electric charge relatively, i.e.
from the zero level, irrespective of the preload. Even with a
preloaded sensor, measurement is therefore always from 0 pC.
At the start of measurement (digital input Measure activated)
the signal output always shows 0 V, which corresponds to
0 pC. The connected sensor can now be loaded (force, strain,
pressure, etc.). If the sensor is unloaded again, the charge is
also reduced again, and the output voltage of the charge am-
plifier consequently drops to 0 V again.
If the digital input Measure is deactivated, measurement is
ended and the output voltage is set to 0 V again. The input
Measure always affects all channels at the same time.

Your 9209 TASK should run in voltage mode not in IEPE mode .  

[zuegesim · Accepted solution]

Alright, so I figured out the issue: it was the charge amplifier. It has a measure and a reset mode; and the signal is non-sensical in the reset mode, which is what I was observing. As soon as I put it into measure mode I got a static signal.

[Henrik_Volkers]

A little RTFM always helps 😉