Analog measurement signals often have to be conditioned so that they can be processed by downstream systems at all. A classic example is the signal amplification of sensors with low voltage levels, such as thermocouples. This signal conditioning prepares the measurement signal for further processing.
Signal conditioning for sensors with charge output
Piezoelectric sensors without integrated electronics have a charge output. Since this charge cannot be processed directly by data acquisition systems, it must first be converted into a proportional voltage. This is done in a charge amplifier. Amplification to the required voltage range, often –10V to +10V, is also done in the charge amplifier. Signal conditioning for the subsequent data acquisition system takes place in the charge amplifier.
Signal conditioning for sensors with IEPE
Piezoelectric sensors with built-in electronics (IEPE) are active measuring elements - they need a voltage supply. This is typically done with a constant current of 4 to 20mA and a compliance voltage of 25V.
Since IEPE sensors are designed to measure dynamic events (AC), this supply of direct current (DC) can be applied to the same signal lines without introducing offset or measurement error.
When using IEPE sensors, the signal conditioner has the task of supplying the sensor with constant current and compliance voltage in addition to signal conditioning and providing the measurement signals for the subsequent data acquisition system.