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Chapter 3 Operation Series 820 Instruction Manual
3-2 IM-82-C
Referencing the Transducer to Non-Standard Conditions
The gas flow rate output of your transducer is referenced to “standard”
conditions of 21°C (70°F) and 760 mm of mercury (1 atmosphere)
unless otherwise specified on the certificate of calibration. Check the
stated reference conditions of your transducer. If you are comparing
your transducer’s output with another type of flow meter, different
reference conditions could cause a discrepancy between the flow
readings.
For example, the output reading of a Top-Trak will be approximately
7% lower when referenced to 0°C rather than 21°C. To find the flow
rate referenced to other standard conditions or the actual temperature
and pressure conditions in the pipe where your transducer is located,
see Appendix A.
Transducer Over-Ranging
If the flow rate exceeds the full scale value listed on the transducer
nameplate, the output signal and digital display (if so equipped) will
read a higher value. The transducer is not calibrated for over-ranged
flows and will probably be both non-linear and inaccurate. Over-
range conditions are indicated by the display and/or output signal
going to a level above the full scale range. When the over-range
condition is removed, it may take several seconds for the transducer
to recover and resume normal operation.
If the supply voltage is only 12 VDC, the over-ranged reading may
exceed the full scale value by 10% maximum. If the supply voltage
is higher, as with the 24 VDC option, then the output can exceed the
full scale by as much as 50%, or more. Digital displays cannot ex-
ceed 3-1/2 digits (1999). If the flow rate exceeds 1999, the right-
most digits will blank and only the left-hand “1” will appear on the
display.