Alnor HM680, Owner'S Manual, Page: 15 / 40

Chapter 3. Getting Started 9
Note:
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.
8.
Once the liquid is flowing steadily from the Low pressure (blue) hose, turn the valve handle on the
manometer to the
MEASURE
position.
Attaching the Hoses to the Test Points
1.
As indicated previously, use an appropriate fitting to connect the open end of the High pressure (red)
hose to the test point with the higher line pressure.
2.
Using an appropriate fitting, connect the open end of the Low pressure (blue) hose to the test point
with the lower line pressure.
Note:
If the hoses are connected in the inverse orientation (i.e. High pressure (red) hose to the
lower line pressure), the displayed High-side gauge pressure (
High P
) will be less than the
Low-side gauge pressure (
Low P
), and the Differential pressure (
dP
) and resulting
calculated flow (
Flow
) will be negative.
Making Pressure Measurements
The HM680 Hydronic Manometer allows for simultaneous measurement and display of the High-side
gauge and Differential pressure. The calculated Low-side gauge pressure is also displayed. While in the
Pressure Measurement screen, the manometer makes and displays continuous pressure measurements, and
allows for discrete data storage to the memory.
Accessing the Pressure Measurement Screen
The Pressure Measurement screen is accessed by pressing the PRESS key from the Flow Measurement
screen, or by pressing the ESC key from any of the primary menus (Main Menu, Data Logging Menu,
and Calculations Menu) when that menu was accessed from the Pressure Measurement screen.
Pressure Measurement Screen
*Shown with the accessory temperature probe attached.
Figure 3: Pressure Measurement Screen
High-Side Gauge
Pressure
Low-Side Gauge
Pressure
*Temperature
Differential
Pressure
Current Test ID
Battery Status or
Power Input Type