Brooks Instrument QMBM - Manual (Page 39)

Section 3 Operation
3-3
Installation and Operation Manual
X-CM-QmB-eng
Part Number: 541B029AAG
June, 2011
QmB Series IP40, IP66, IP66XP
Zero Procedure
1. Prepare the instrument for zeroing:
a. Install the instrument according to the instructions in this manual.
b. Power-up sequence. Isolate device from flow pressure when
applying power. Once the status indicator is illuminated green,
pressure may be applied.
c. Apply power to the instrument and allow approximately 45 minutes
to reach a stable condition.
d. Run the process fluid to be measured and controlled through the
instrument until the temperature of the instrument approximates
the normal process operating temperature. Use the Valve Override
(V.O.R.) function to fully open the control valve to facilitate
temperature stabilization.
2. Once the instrument has reached process temperature, close the
external shutoff valve downstream from the instrument and wait for the
flow to stop. Set the control function to zero and V.O.R. to normal once
flow has stopped and all pressure differential across the instrument has
been bled off.
3. Make sure that the instrument is completely filled with the process fluid
under normal process conditions of temperature, pressure, density, etc.
make sure there is no entrapped gas in the sensor tube and ensure a
zero flow condition through the instrument.
4. After confirming that fluid flow through the instrument is completely
stopped, actuate the zero function as previously stated.
5. The default zero sample interval is 30 seconds. A successful zero
operation on the controller and meter will be indicated by a solid green
color status LED. A solid red color status LED indicates a failed zero
process. A non-steady flash will indicate a failed condition. A failed
condition can only be cleared by a power cycle.
6. Once the status LED turns green, zero process is complete and the
instrument is ready for operation.
Please note that zero command will only be accepted when the output
change is less than 1% of the maximum full scale of the device. This logic
prevents an accidental zero command from being initiated when flow is
present, through the device.