Dwyer TFM-LP - Manual (Page 17)

F-20-TF-L, pg. 17 of 30
A second empirical check should be made at a flow rate below the
maximum for the unit e.g. at 50% of full scale. The calculated percentage
error at this flow should then be compared to the error at maximum flow. If
there is a big difference in the percentage errors then the flow signal is no
longer linear and the unit may be damaged (consult Dwyer Customer
Service).
Once it has been determined that the linearity is still acceptable and the
error in flow reading at maximum flow has been calculated, there are 3
options:
i.) Minor adjustments to actual calibration of the flow sensor may be made
by turning the gain potentiometer on the side of the unit. For example:
For a unit with a flow range of 13-100ml/min and a
0-5VDC output:
With a constant flow and constant 5VDC output the actual volume
measured over 60 seconds was 103ml.
The correct voltage output for a flow of 103 ml/min is:
(5/100) x 103 = 5.15 V
With the flow at a constant 103 ml/min the gain potentiometer
should be carefully adjusted so that a voltage output reading of
5.15 V is obtained.
If the unit cannot be suitably adjusted please contact Dwyer Customer
Service. Pulse outputs are not adjustable.
Adjusting the Gain Potentiometer Using a Flat Head Screwdriver
(TFP-LP Series shown, other models similar)