Alnor HM680, Owner'S Manual, Page: 16 / 40

10 HM680 Hydronic Manometer
High-Side Gauge Pressure
The High-side gauge pressure measurement is indicated as
High P
on the manometer display.
Low-Side Gauge Pressure
The Low-side gauge pressure reading is indicated as Low P on the manometer display. It represents a
calculated value determined from the measured High-side gauge and Differential pressure as follows:
Low P = High P - dP
Differential Pressure
The Differential pressure measurement is indicated as dP on the manometer display.
Continuous Measurements
The HM680 Hydronic Manometer makes and displays continuous pressure measurements whenever the
manometer is in the Pressure Measurement or Flow Measurement screen, with the exception of when the
READ key is pressed. The displayed readings are averaged measurements taken over the sampling period
as defined by the current time constant setting. The display is updated once per second.
Making Flow Measurements
The HM680 Hydronic Manometer allows for continuous calculation and display of flow. While in the
Flow Measurement screen, the manometer makes and displays continuous pressure measurements,
calculates and displays continuous flow readings, and allows for discrete data storage to the memory.
Note:
The
Cv (Kv)
value of the measured valve must be known in order to obtain meaningful flow
readings
.
Accessing the Flow Measurement Screen
The Flow Measurement screen is accessed by pressing the FLOW key from the Pressure 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 Flow Measurement screen.
Flow Measurement Screen
*Shown with the accessory temperature probe disconnected.
Figure 4: Flow Measurement Screen
Current Cv (Kv)
factor name
*Temperature
Differential
Pressure
Flow
Current Test ID
Battery Status or
Power Input Type
Current Cv (Kv)
factor value