The charge output
by a piezoelectric transducer is converted into a directly proportional voltage by means of a charge amplifier.
Piezoelectric sensors are ideally suited for dynamic, i.e. non-zero point-related measurements. The drift generated by piezoelectric measurement chains is so low that it does not affect accuracy even with high requirements.
The drift is an effect of the charge amplifier
. The transducers themselves do not display drift if mounting and connection are implemented correctly. The maximum drift
of a measurement chain is 0.1 pC/s or 25 mN/s if quartz is used as sensor material and 13 mN/s for the sensor material gallium phosphate.
In order to achieve a lower drift, please note the following two points:
1. Running-in behavior of the charge amplifier
The charge amplifier should run in at least a hour before measurements start.
2. Cleanliness of the connections
If the insulation resistance
of the cable between transducer and charge amplifier is too low, the measurement chain will drift as charge will discharge via the too low insulation resistance. In order to keep the piezoelectric measurement chain drift low, all plugs and sockets must be kept clean at all times.
Please ensure that you do not touch open contact surfaces
with the hand as this reduces the required insulation resistance.
We also recommend that protective caps
(scope of delivery) should be left on the sockets of the sensors and charge amplifiers until the sensor or charge amplifier is connected. When the connections are disconnected, the protective caps should be screwed back on again.
Piezoelectric transducers must be connected with a charge amplifier with a high quality coaxial cable, HBM offers the cable 1-KAB143/3 for this purpose. Such a cable cannot be repaired, it must be replaced if damaged
If the measurement chain is always operated with a connected cable and the sensors always stored with protective caps, then contaminated contact surfaces do not generally occur.