Changes in ambient temperature affects the accuracy of gauges in several ways.
Range Shift
Range shift is caused by the change in modulus of elasticity of
the bourdon. This effect increases proportionately as the pressure increases. As a general
rule, the loss of accuracy will be an additional 1% of full scale reading for every 50
degree F change in temperature.
Zero Shift
Zero shift is created by the change in physical
dimensions of the various components brought about by the temperature change. This
shift is constant over the entire scale and does not vary with applied pressure.
Maximum Temperature Limits
To ensure longest, possible life and accurate readings,
pressure gauges that have soft-soldered pressure joints should not be exposed to process
or ambient temperatures over 120 degree F. This is especially true of pressure gauges
with liquid filled cases, due to the expansion of the case fill fluid. Long term exposure to
temperatures in excess of 120 degree F may cause discoloration of dials and fill fluids, as
well as hardening of the case seals and possible fill leakage.
Gauges with silver soldered or welded pressure joints should not be exposed to process or
ambient temperatures over 190 degree F.
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