Humboldt H-2786C Air Meter - Manual (Page 4)

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4. Pump up air pressure to a little beyond the pre-determined initial
pressure line.
5. Wait a few seconds for the compressed air to cool to ambient tem-
perature, then stabilize the gauge hand at the proper initial pressure
point by pumping or bleeding off as needed.
6. Close both petcocks and immediately crack open the “hands-free”
valve, exhausting air into the base.
7. Wait a few seconds until the hand is stabilized. If all the air has been
eliminated and the initial pressure line was correctly selected, the
gauge should read 0%. If two or more tests show a consistent varia-
tion from 0%, then change the initial pressure line to compensate for
the variation. Use the newly established “initial pressure” point for
subsequent tests.
8. Screw the curved tube into the outer end of the threaded petcock.
Controlling the flow with the petcock lever, fill the 5% calibration
vessel to its full capacity (354ml) with water from the base of the air
meter.
9. Close the “hands-free” valve.
10. Release the air at the free petcock. Open the other petcock and let
the water in the curved pipe run back into the base. There is now 5%
air in the base.
11. With the petcocks open, pump air pressure in the exact manner
as outlined in step 4. Close petcocks and immediately open the
“hands-free” valve. Wait a few seconds for the needle to stabilize
and for the exhaust air to warm to ambient temperature. The dial
should now read 5%.
12. If two or more consistent tests show that the gauge reads incorrectly
at 5% air (in excess of 0.2%, or whatever is considered satisfactory),
then remove the gauge glass and reset the dial hand to 5%. Do this
by turning the recalibration screw, located just below and to the
right of the center dial.
13. When the gauge hand reads correctly at 5%, additional water may
be withdrawn in the same manner to check results at 10, 15, 20%,
etc.
Maintenance Tips
1. Prompt cleaning with water of the air meter cover and pot, both
inside and out will ensure a proper seal and volume are maintained.
2. Periodic oiling of petcock screws will prevent them from seizing.
WD-40 or a similar product is sufficient.