Method 3 (Ambient Pressure Air Calibration Test)
1. While firmly grasping the enclosure, loosen the compression
fitting at the top of the ball valve.
2. Slowly withdraw the stem until the flats located on the sensor
are exposed.
3. Carefully close the ball valve and fully withdraw the flow
meter.
4. Place the flow sensor in to an empty water bottle.
5. Wait up to 2 – 3 minutes to allow the meter reading to stabilize at zero and note the
mW reading on the display.
6. Compare the reading to the zero flow air calibration shown on the laminated tag
attached to the meter. The two readings should agree within ± 5mW.
7. At the conclusion of the test, re-install the meter as per the instruction manual.
IMPORTANT NOTE
The ambient pressure air calibration test can be used to validate the meter calibration independent
of the process fluid. As such, this test can be a useful diagnostic tool.
i
Method 2 (Used when it is not possible to stop flow in the pipe.)
1. While firmly grasping the enclosure, loosen the
compression fitting at the top of the ball valve.
2. Slowly withdraw the stem until the bottom of the flats
located on the sensor is just exposed.
3. Re-tighten the compression fitting to ½ turn beyond
hand tight.
4. Carefully close the ball valve.
5. Wait up to 2 – 3 minutes to allow the meter reading to
stabilize at zero and note the mW reading on the display.
6. Compare the reading to that stamped on the nameplate.
The two readings should agree within ± 5mW.
7. At the conclusion of the test, re-install the meter as per
the instruction manual.
Interpreting Test Results
Zero flow calibration test readings that are within ± 5mW of the original calibration value indicate
that the meter calibration is still valid.
Zero flow calibration test readings that are within ± 10mW of the original calibration value indicate
that the meter calibration is still valid, but the test results were likely influenced by external factors.
These include any or all of the following:
1. Sensor orientation (installed horizontally).
2. Dirt or debris is coating all or part of the sensor assembly.
3. Process fluid composition different from the fluid used during calibration.
(Use ambient air calibration test to confirm.)
4. Residual flow readings during test due to leaking valves or sensor movement.
(Repeat test using alternate method.)
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