Alnor HM680, Owner'S Manual, Page: 14 / 40

8 HM680 Hydronic Manometer
The zero offset of the gauge pressure sensor is sensitive to temperature changes. If moving
the manometer between areas of extreme temperature difference, it is best to allow the meter
to settle to the new temperature prior to zeroing.
Zeroing the Differential Pressure Sensor
To ensure the most accurate differential pressure ( dP ) measurements and calculated flow ( Flow ) values,
the HM680 differential pressure sensor should be zeroed prior to taking readings on each new system.
The differential pressure sensor is zeroed as follows:
1.
Turn the valve handle on the manometer to the BYPASS position.
2.
Follow the on-screen instruction to complete the differential pressure sensor zeroing process.
Notes:
Zeroing of the differential pressure sensor is unaffected by pressures applied to the meter
during zeroing. This feature allows for successful zeroing of the differential pressure sensor
while maintaining connections to the system under test.
Zeroing of the differential pressure sensor is initiated any time the valve handle has been
turned to the
BYPASS
position while in the Pressure or Flow Measurement screens. This
feature allows for successful zeroing of the differential pressure sensor while entrained air is
being purged from the hoses.
The zero offset of the differential pressure sensor is sensitive to temperature changes. If
moving the manometer between areas with extreme temperature difference, it is best to allow
the meter to settle to the new temperature prior to zeroing.
Connecting the Manometer to the Test Points
Attaching the Hoses to the Manometer
1.
Connect the straight female flare fitting on the High pressure (red) hose to the male fitting on the top
of the manometer marked with a plus (
+ ) sign.
2.
Connect the straight female flare fitting on the Low pressure (blue) hose to the male fitting on the top
of the manometer marked with a minus(
-
) sign.
Bleeding the Entrained Air
To ensure the most accurate pressure measurements, all entrained air within the hoses should be purged as
follows:
1.
Turn the shut-off ball valve on both the High and Low pressure hoses to the closed position.
2.
Turn the valve handle on the manometer to the
MEASURE
position.
3.
Using an appropriate fitting, connect the open end of the High pressure (red) hose to the test point
with the higher line pressure.
4.
Attach the appropriate fitting to the open end of the Low pressure (blue) hose.
5.
Place the open end of the Low pressure (blue) hose in a suitable receptacle or near a drain.
6.
Turn the shut-off ball valve on both the High and Low pressure hoses to the open position.
7.
Turn the valve handle on the manometer to the
BYPASS
position to allow the liquid flow to displace
the entrained air.