Piezoelectric Signal Conditioning Module

Piezoelectric crystals generate charge, not voltage. A charge amplifier converts that charge directly into a voltage, making the signal insensitive to cable length and capacitance—important for industrial runs. A voltage amplifier measures the voltage across the sensor's capacitance, which changes with cable length. If you have more than a couple meters of cable or operate in electrically noisy environments, a charge amplifier module (which is what our conditioners use) tends to give cleaner results.

You start by looking at the maximum vibration you expect. Suppose your accelerometer gives 50 pC/g and the peak vibration is 20 g. That’s 1000 pC into the conditioner. If the conditioner’s maximum input is, say, 10 000 pC, a gain of 10 mV/pC would yield 10 V full scale—just right for a ±10 V DAQ. Our modules typically have a coarse sensitivity selector and a fine vernier knob so you can dial in the exact setting.

Several configurations provide a constant current source for IEPE sensors, often switch-selectable. That way, the same module can feed 4 mA to an integrated circuit piezoelectric sensor or act as a pure charge amplifier for high-temperature charge-mode sensors. Check the model’s front panel or datasheet for the ICP/charge toggle.

A low-pass filter blocks frequencies above your zone of interest—this prevents aliasing in the digitizer and removes high-frequency noise from the signal. Our modules typically offer multiple corner frequencies, like 100 Hz, 1 kHz, or 10 kHz, selected by a rotary switch. Some versions also include a high-pass filter to remove slow thermal drift or DC offsets, which is handy when monitoring very low-frequency events like seismic vibrations.

We provide a 4–20 mA output option for process control loops. The internally converted current signal is proportional to the selected vibration range—for instance, 4 mA at zero vibration and 20 mA at the full-scale value you set via the gain controls. You just wire the output to a PLC analog input module and configure the scaling in your software. The loop power is typically provided by the PLC itself.