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Manual 111-082010_Nall Mass Flowmeters Page 15 of 23
7.0 TEMPERATURE EFFECTS
7.1 Ambient Temperatures:
7.1.1 Transducer
In order to maintain the accuracy of the flowmeter with changes in ambient temperature, it is necessary to
keep the temperature of the transducer between 10° C and 50° C. (The temperature of the base is normally
about 10° C above ambient due to internal heat.) There are two ¼”-20 bolt holes in the bottom of the
transducer to facilitate mounting the transducer to an external heat sink. Since some of the temperature shift
results in a slight zero offset, better results are obtained if the flowmeter is re-zeroed at the operating
temperature.
7.1.2 Power Supply
The NALL-type power supply can be operated over an ambient temperature range of 0° C to 40° C without
causing a calibration shift of more than +/- 1% of full scale. Since this error is primarily a zero shift, it can be
eliminated by adjusting the flowmeter ZERO potentiometer at the given operating temperature.
7.2 Gas Temperature
No corrections for gas temperature between 0° C and 100° C are necessary for the small ranges, but some
correction may be necessary for higher ranges. Part of the error at high ranges is transitory, and in most
cases will be reduced when the transducer temperature and gas temperature reach an equilibrium condition.
Gas flow at temperatures between -50°C and + 200° C can often be measured, but require recalibration by
the customer at operating conditions. Consult the factory for further details.
When using the NALL – or NALL –P Series flowmeter with a Laminar Flow Element, it is recommended
that both the Laminar Flow Element and the HS-10S (or HS-10M) transducer operate at the same
temperature.
The Hastings Linear Mass flowmeter measures GAS flow. DO NOT let the temperature and/or pressure of
the gas reach a point that would cause the gas to change to a liquid state, or erroneous indications will result.