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9.0Calibration
9.1CALIBRATION PROCEDURES
The Hastings Mass Flowmeter has been carefully inspected and calibrated at the factory before shipment and will give long, reliable service. Calibration is stable, and recalibration is seldom necessary under normal operating conditions; however, to maintain optimum accuracy it is advisable to check calibration on an annual basis. The unit may be returned to the factory for this purpose, but if that is undesirable, the following calibration procedure may be of assistance:
1.Connect the power supply to the proper power source (Section 3.4).
2.Turn the power supply “ON” and allow 30 minutes for
3.Set the “electrical zero” (Section 3.5).
4.Connect the inlet side of the transducer through a metering valve, to a
5.Check transducer heating voltage as outlined in Section 10.2.1.
6.During normal calibration, a flowmeter is spanned at 80% of full scale to obtain best average linearity.
Example: A 50 SCCM flowmeter with
=40 SCCM) of full scale. At this flow rate, the voltage at the binding posts should read 4 VDC (80% X 5 VDC).
CAUTION: Most flow standards are volumetric devices and must be corrected for temperature and pressure to standard conditions of 0oC and 760 Torr. This correction amounts to several percent at normal room temperatures and pressures and should not be neglected.
7.If the flowmeter does not agree with the reference flow standard, it is first necessary to correct the output at the binding posts. This is done by making a small adjustment to the “GAIN” potentiometer
8.If the meter reading (flow) does not correspond with the binding post’s output (voltage), make a small adjustment to the “METER” trim potentiometer
9.
Manual | Page 18 of 23 |