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Manual 111-082010_Nall Mass Flowmeters Page 13 of 23
Example: (A) What is the output sensitivity of HS-1KS?
(B) What is the flow rate for a 2.71 volt output?
Solution: (A) Sensitivity = rated flow
Rated output
= 1000 SCCM
5.00 VDC
= 200 SCCM/VDC
(B) Mass Flow = output X sensitivity
= 2.71v X 200 SCCM/VDC
= 542 SCCM
5.7 Accuracy:
The accuracy of the flow indication is +/- 1% of full scale, with the exception of the U-Series transducer
where the accuracy is +/- 3% of full scale.
5.8 Repeatability:
The repeatability over a six-month period is +/- ½% of full scale if the flowmeter is operating normally in a
clean, dry system. Under reasonable constant conditions, a repeatability of +/- 1 to +/- 2% of
INDICATION can be expected on a day-to-day basis.
5.9 Over-range:
The flowmeter has an output signal which is directly proportional to mass flow and linear to +/- of full scale
from zero flow to the normal full-scale flow rate.
The flowmeter can be used to measure flow rates higher than the rated maximum flow, but the output signal
normally becomes non-linear above 5 volts d-c. A calibration curve for voltage vs. flow can be made for
outputs up to 10 volts d-c. At some point above 10 volts d-c the output will no longer increase as the flow
increases. The flow rate required to produce this condition is several times the normal full-scale flow rate.
Once flow is reduced to the proper level, the flow meter will again indicate mass flow currectly. The
flowmeter will not be damaged by excessive flow rates as long as the pressure in the line does not exceed the
pressure rating for the transducer.