HBM claims that large cost savings can be achieved when conducting
experimental stress analysis tests by removing the need for connection
cables, and one way to do this is to use a fieldbus. The company's new
CANHead CANbus based system works by making the base module independent
of the amplifier module, allowing amplifiers to be located close to the
measuring points. The data gathered during tests is transmitted via a
standard CANbus fieldbus to the base module.
In addition to reducing the cable overhead - significant when there are
literally thousands of test points to connect up - CANHead allows the
test preparation to take place before the amplifier is installed. As an
added advantage, the amplifier can be disconnected at any time without
the intelligent base module losing its data. Each unit has a capacity of
ten channels and provides an A/D converter on each channel for
synchronous data acquisition.
Data from up to 12 CANHead modules can be transmitted over a single
CANbus line using the CANopen protocol. The amplifiers operate on a 600Hz
carrier frequency to eliminate thermal voltages at the contact points and
dc voltage drift.