Teledyne NALL Temperature Effects, Ambient Temperatures Transducer, Power Supply, Gas Temperature

7.0TEMPERATURE EFFECTS

7.1Ambient Temperatures:

7.1.1Transducer

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.

7.1.2Power 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.

7.2Gas 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.

Manual 111-082010_Nall Mass Flowmeters Page 15 of 23