IEPE is a set of initials for “Integrated Electronic Piezo Electric”. It is a standard for electronics in transducers (like accelerometers and microphones) that have built-in amplifiers.
ICP is short for “Integrated Circuit-Piezoelectric”. ICP is a trademark name of PCB Corporation for their proprietary implementation of IEPE (hence it is the same thing). Other trademark names of IEPE from different companies include CCLD, IsoTron or DeltaTron.
Because Simcenter SCADAS hardware can power an IEPE accelerometer (by selecting ICP mode in the input mode of Channel Setup worksheet), it is not necessary to have an external amplifier.
You can just plug the accelerometer directly into the SCADAS as shown below.
An IEPE/ICP transducer cannot measure offsets because they are AC coupled, and all DC content is removed. Only dynamic data can be measured. The bias voltage supply for the transducer is a constant DC voltage which is supplied on the same wire as the signal, and is filtered out from the data by a high pass AC coupling filter.
ICP and Charge accelerometers both measure vibration, but operate quite differently:
- An ICP accelerometer outputs a voltage porportional to vibration. A typical calibration value is in mV/g, for example 100 mV/g.
- A charge accelerometer outputs charge porportional to vibration, expressed in picoCoulombs. A typical calibration value is expressed in pC/g. For example, 31.6 pC/g.
To measure either one, you will need the appropriate card in your SCADAS. If you have a ScadasMobile VC8 card, you can measure either ICP or Charge accelerometers.
In Simcenter Testlab, use the pulldown under "Input Mode" to select either Charge or ICP. This is selectable on a per channel basis.
Note that the cable connectors of ICP and Charge are typically very different. Charge accelerometers require a tight electric connection, so typically a threaded 10-32 connection is used. A BNC cable connector is typically used for ICP accelerometers.
If you are considering whether to buy charge or ICP accelerometers, one of the main reasons to opt for one or the other is temperature related. Typically, charge accelerometers have a higher operating temperature range than ICP. ICP accelerometers have been continually improving over the years in this regard, but still do not cover the same temperature range. Check the specifications. If you are measuring on a hot exhaust or engine manifold, charge accelerometers may be the only option.
If you mix ICP and charge accelerometers on the same test, be warned that for the same vibration signal, the phase is 180 degrees different between ICP and charge. This would be important if doing an Operational Deflection Shape.
It also possible to use a charge accelerometer with a Scadas that has only Voltage/ICP by using an external converter. PCB makes an external inline converter that allows a charge accelerometer to be powered using ICP.
PCB Model number is 422E51.