Omega Engineering FLR 1000 Series, User Manual

Page: 15 / 29

pg. 15 of 29
If the unit has a flow reading of 200ml/min then the corrected flow
reading (for CO2) would be:
Corrected Flow = 200 X 0.88 = 176 ml/min
CAUTION:. The use of correction factors can be subject
to inaccuracy and errors of up to ±10%. Please contact
the Omega Engineering Service Department if accurate,
certified recalibration is required.
Calculating a correction factor for a gas enables the calibration of the unit
to be adjusted for that gas. This is accomplished by:
i) Calculate the corrected flow reading or VDC output at 100% of
flow using the above formulas.
ii) Adjust the flow of (the new) gas to give this flow reading
iii) Maintain this flow and ensure a stable reading.
iv) Adjust the gain potentiometer on the unit so that a 5VDC output
is obtained. The unit is now calibrated for the new gas.
For example: A 2.0 -10.0 l/min unit that has been calibrated for Air is to
be used with CO
2
. The correction factor, calculated as above, is 0.88.
When flowing CO
2
the unit will read high i.e. at 5VDC the flow of CO
2
would actually be 8.8 l/min and not 10 L/min. A flow of 10 l/min of CO
2
through the unit would give a reading of 10/0.88 = 11.36 l/min or 5.68
VDC on the unit. Flow should be adjusted so that an output of 5.68VDC or
reading of 11.36l/min is obtained. The gain potentiometer is then adjusted
so that the voltage output becomes 5VDC or the display reads 10l/min.
The unit has now been adjusted for CO
2
and no further corrections to flow
readings are required (if flowing CO
2
).
It should be noted that the maximum output voltage for the units is
approximately 5.9VDC. It is not possible to adjust units if an output of
greater than 5.9 VDC is required.
Adjusting the Gain Potentiometer Using a Flat Head Screwdriver
(FLR 1000 shown, other models similar)