Subhead measuring amplifiers for optimum signal conditioning

December 12, 2012 // By Julien Happich
The isolating 5B measuring amplifiers of BMC Messsysteme provide for optimum signal conditioning, effective noise suppression, and protection against high potentials.

When measuring a signal, if the DAQ system, PC, and power supply have a different ground reference, a compensating current occurs. In the most harmless case, only the signal will be distorted. Not separating potentials, however, is often the cause for destroying the measurement system. Isolation is the suitable method here. It's a popular fallacy to think differential measurement is the solution for noise-free measuring results. In this case, "only" the voltage difference between two analog connections is measured. A static or dynamic increase of the real signal potential – the so-called common-mode voltage – adds up to the measuring signal. The permitted input voltage of the DAQ system can easily be exceeded. When testing a battery, for example, the (low) voltage of each single cell is measured. Common-mode voltages generated by the other battery cells and not being separated can make the measured signal useless or be a serious danger to the DAQ system. Again galvanic isolation is the answer.

Sensors often provide signals in the millivolt range. A pre-connected measuring amplifier allows for optimum signal adjustment to the whole input range of a DAQ system. The system is used to its full extent and tiniest signal changes can be detected. The 5B measuring amplifiers of the MA series feature triple galvanic isolation between measuring signal, PC data acquisition system, and power supply. This provides maximum interference resistance and maximum protection for the measurement system. The measuring amplifiers feature a sensor supply as well as various measuring ranges and filter cut-off frequencies set with DIP switches at the module. Offset and Gain are calibrated via potentiometers. The measuring converters are available in three versions, the MA-U (50kHz bandwidth), the MA-UI with selectable measuring ranges for optimum adjustment to voltage and current signals, and the universal measuring amplifier MA-UNI for measuring not just voltage and current but also other physical quantities (resistance, temperature, strain gauge, carrier frequency, etc.). For easy