(Above) PFI's 28008 (8-card) modular mainframe with a combination of bridge conditioner cards
To fully realize the noise suppression provided by Precision Filters' bridge and strain conditioners, make sure your measurement circuit is balanced.
A primary function of a bridge conditioner in a strain gage circuit is the differential amplification of small changes in resistance caused by gage deformation. In addition to boosting the strain signal, the differential amplifier will greatly suppress any voltage that is common to both of its inputs. If that voltage represents noise picked up by the circuit, then the amplifier will significantly improve the signal-to-noise ratio (SNR) of the measurement - an improvement that is commonly specified in terms of the amplifier's common mode rejection ratio (CMRR).
In a recent white paper, PFI explains why full realization of the high CMRR provided by their bridge conditioners requires a balanced measurement circuit. This can be accomplished using a traditional Wheatstone Bridge with voltage excitation, provided all gages and completion resistors are collocated. However, a simpler setup is made possible by PFI's Balanced Constant Current (BCCTM) technology, allowing for as few as 2 wires between an active strain gage and the signal conditioner.
Precision Filters (PFI) offers a complete line of bridge conditioners for measuring static and dynamic strain (including high temperature strain), RTDs, thermocouples, IEPE sensors or any bridge-type transducer including pressure sensors, piezo-resistive accelerometers, load cells and more. We offer models with an analog bandwidth greater than 1 MHz and programmable filter selections between 1 Hz and 200 kHz. Choose from our line-up of four or eight channel cards with performance to match your requirements.
All of PFI’s bridge conditioners have built-in test hardware that makes automated system verification and validation easy. The test bus enables automated calibration signal insertion at the amplifier input. Any output channel may be observed without disrupting the normal output using the monitor bus. Our four channel cards have real time monitoring of excitation, transducer loop resistance, sensor leakage to ground and more. Never before has a system provided you with so much pre-test confidence that your measurement circuit is functioning properly.