Readout units and the calibration of loadcells. Date : 31 July 2017 Sipho Dlamini Test and Measurement Conference 2017

CONTENTS Introduction Readout units and force calibration of loadcells Force laboratory at NMISA Force machines Force transducers (loadcells) Measuring amplifiers (readout units) Readout units and force calibration of loadcells Calibration of readout units Conclusions

The Force laboratory at NMISA National measurements institutes (NMIs) of countries around the world are usually tasked with maintenance of measurements systems and standards. The force laboratory at NMISA is tasked with the maintenance and dissemination of the standard unit of force (Newton) Maintaining and dissemination of force standard Capability to generate force Capability to measure the force generated accurately Calibration

Capability to generate force NET DOWNWARD VERTICAL FORCE

Capability to measure the force generated accurately

Calibration

The readout unit should not pick up noise from outside sources The readout must not add noise to the signal and, if possible should reduce or remove any noise that is already in the signal from the loadcell. The readout unit should not pick up noise from outside sources Performance should not be affected by ambient temperature for those readout units that must operate in extreme environment The performance of a readout unit must be stable over time

Connection cables

Calibration of readout unit units The performance of a readout unit must be stable over time

Calibration of readout unit units (Stability)

Calibration of readout unit units (Stability)

Performance should not be affected by ambient temperature for those readout units that must operate in extreme environment

Calibration of readout unit units (cable configuration)

Conclusions For force measurements Stability of readout units should be monitored Readouts are generally stable over long periods of time Connection cables can influence calibration measurements 6 wire configuration vs 4 wire configuration

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