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

3
Operation Instructions
1. Fill the base with a sample of fresh concrete, placing it in the
base by vibrating or tamping, in much the same manner as the
concrete is to be placed on the job. Strike off the base, level full,
with the bronze straight edge furnished. Wipe top edge clean.
2. Clamp cover on with petcocks open.
3. Using rubber syringe, inject water through one petcock. Leave
petcocks open.
4. With built-in pump, pump up air to “initial pressure” line on gauge.
5. Wait a few seconds for compressed air to cool to normal
temperature and then bleeding off, as needed.
6. Close both petcocks and press down on “thumb lever” to release
the air into the base. Hold thumb lever down for a few seconds,
lightly tapping the gauge with the finger to stabilize the hand
on dial.
DO NOT TILT THE METER AT ANY TIME.
7. Read percent of air in concrete on dial.
8. Open the petcocks to release the pressure and then remove cover.
Clean up the base, cover and petcock openings.
To Check Calibration of Meter Gauge
1. Fill the base full of water.
2. Screw the short piece of straight tubing into the threaded
petcock hole on the underside of the cover. Clamp cover on the
base with the tube extending down into the water.
3. With both petcocks open, add water with syringe through the
petcock having the pipe extension below, until all air is forced out
opposite petcock. Leave both petcocks open.
4. Pump up air pressure to a little beyond the pre-determined initial
pressure line. Wait a few seconds for compressed air to cool to
normal temperature and then stabilize the gauge hand at the
proper initial pressure line by pumping or bleeding off as needed.
5. Close both petcocks and immediately press down on the thumb
lever exhausting air into the base. Wait a few seconds until the hand
is stabilized. If all the air was eliminated and the initial pressure line
was correctly selected, the gauge should read 0%. If two or more
tests show a consistent variation from 0% in the result, then change
initial pressure line to compensate for the variation. Use the newly
established “initial pressure” line for subsequent tests.