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Force, pressure, mass and density

Load indicators (DC ratio meters)

Accredited calibration

A UKAS-accredited calibration service of DC ratio meter indicators for force transducers. This is delivered using precision digital voltmeters traceable to national standards, to meet the requirements specified in the 2011 version of BS EN ISO 376.

DC ratio meters enable flexibility as they can be interchanged between measurement systems without loss of traceability as their design eliminates the effect on the load cell output of any small variations in input voltage. They energise a load cell, typically with a voltage of 10 V and measure the input and output voltages, displaying the ratio of the two in mV/V.

DC ratio meter calibration service

NPL calibrates DC ratio meters against reference resistances, using precision digital voltmeters traceable to national standards. Ranges available for calibration of DC ratio meters:

  • 0.01 mV/V to 0.05 mV/V, expanded uncertainty 0.010 %
  • 0.05 mV/V to 1.0 mV/V, expanded uncertainty 0.005 %
  • 1.0 mV/V to 2.5 mV/V, expanded uncertainty 0.007 %
  • 2.5 mV/V to 10 mV/V, expanded uncertainty 0.005 %

Interchange of ratio meters

Greater flexibility is achieved when the DC ratio meter is calibrated both separately from and together with the force transducer. This allows the ratio meter, should it be damaged, to be repaired and recalibrated, or replaced by another calibrated ratio meter, without affecting the transducer’s calibration. International standards permit the interchange of voltage ratio meters providing:

  • The ratio meter has a calibration certificate in the same electrical units, traceable to national standards.
  • The range and resolution of the meter is equal to or greater than that of the meter being replaced.
  • The meters agree within ±0.1 % over the full working range.

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