25% Flow Adjustment; 100% Flow Adjustment; Lcd Display Scaling; Access Lcd Display Circuit - Aalborg GFM 17 Operating Manual

7.3.3 25% Flow Adjustment

Reconnect the gas source. Using the flow regulator, adjust the flow rate to 25% of
full scale flow. Check the flow rate indicated against the flow calibrator. Adjust the set-
ting for potentiometer [R33] by using the insulated screwdriver through the access
window, until the output of the flow meter reads 1.25VDC ±63mV (or 8mA ±0.25mA).
7.3.4 50% Flow Adjustment
Using the flow regulator, increase the flow rate to 50% of full scale flow. Check the
flow rate indicated against the flow calibrator. The output of the flow meter should
read 2.50VDC ±63mV (or 12mA ±0.25mA). If the reading is outside of that range,
place the jumper at [J1] as appropriate to increase or decrease the signal. Adjust
the setting for potentiometer [R38] by using the insulated screwdriver through the
access window, until reading is within specification.
7.3.5 75% Flow Adjustment
Using the flow regulator, increase the flow rate to 75% of full scale flow. Check the
flow rate indicated against the flow calibrator. The output of the flow meter should
read 3.75VDC ±63mV (or 16mA ±0.25mA). If the reading is outside of that range,
place the jumper at [J2] as appropriate to increase or decrease the signal. Adjust
the setting for potentiometer [R39] by using the insulated screwdriver through the
access window, until reading is within specification.

7.3.6 100% Flow Adjustment

Using the flow regulator, increase the flow rate to 100% of full scale flow. Check
the flow rate indicated against the flow calibrator. The output of the flow meter
should read 5.00VDC ±63mV (or 20mA ±0.25mA). If the reading is outside of that
range, place the jumper at [J3] as appropriate to increase or decrease the signal.
Adjust the setting for potentiometer [R40] by using the insulated screwdriver
through the access window, until reading is within specification.
Repeat steps 7.3.3 to 7.3.6 at least once more.
7.4

LCD Display Scaling

It may be desirable to re-scale the output reading on the LCD readout supplied
with certain model GFM transducers. Re-calibration for a new flow range or dif-
ferent engineering units are two examples of when this may be necessary.
7.4.1

Access LCD Display Circuit

Carefully remove the LCD from the GFM or panel mounted surface. Remove the
aluminum housing on the side of the connection cable. Slide the LCD assembly
out of the aluminum housing.
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