HM685 QUICK START GUIDE
The ▲and ▼keys are used to navigate through menus or to select an item to change.
The ◄ and ► keys are used to change the selected item.
The ESC key returns to the previous screen or cancels an operation without saving changes.
Pressing the ENTER key accesses the Main Menu, select a menu item or accept changes.
Pressing the READ key initiates taking a time-averaged reading based on Log Mode and Log
Settings. After taking the reading, the values are stored to memory (current Test ID) and displayed
on screen for a period of four (4) seconds or until the READ key has been pressed again. The
READ key also updates the calculations with current readings in the CALCULATIONS Menu.
Press the BACKLIGHT key to turn the display’s backlighting on or off.
Press the DATA key from a measurement screen to access the Data Logging Menu.
Accesses the Pressure measurement screen from the Flow measurement screen.
Press the key to turn the HM685 Hydronic Manometer on or off.
Accesses the Calculations menu from the Flow or Pressure measurement screen.
Accesses the Flow measurement screen form the Pressure measurement screen.
Key Pad
Each key and its function are described below.
Instrument Power
The HM685 Hydronic Manometer can be powered by four (4) AA-size batteries (alkaline or rechargeable NiMH)
or the AC adapter.
Battery Installation
Locate the battery cover on the back of the unit and loosen the screw to remove. Take out the battery holder and
replace with fresh batteries (alkaline or rechargeable NiMH). Ensure that the batteries are correctly oriented within
the battery holder and Set the battery-type selection switch to indicate the type of batteries to be used (alkaline or
rechargeable NiMH). Reinstall the battery holder and battery cover.
Using the AC Adapter
The AC adapter allows the HM685 Hydronic Manometer to be powered from a standard AC wall outlet. When
using the AC adapter, alkaline batteries (if installed) will be bypassed. The AC adapter also charges the NiMH
type batteries (if installed) in the unit.
Zeroing the Gauge Pressure Sensor
Upon instrument start-up, the user will be prompted to zero the gauge pressure sensor and includes on-screen
instructions. Gauge pressure sensor zeroing can also be initiated by selecting Zero Gauge Pressure when in the
Main Menu by pressing the ENTER ( ) key. The (+) and (-) pressure ports must be open to atmosphere and
the valve handle on the manometer set to the MEASURE position.
Zeroing the Differential Pressure Sensor
High Side
Pressure
Temperature
Low Side
Pressure
Differential
Pressure
Battery Status
or Power
Input Type
Current
Test ID
Turn the valve handle on the manometer to the BYPASS position while in the main Measurement Screen to
automatically zero the differential pressure sensor. Zeroing of the differential pressure sensor occurs any time the
valve handle is turned to the BYPASS position. Any pressures applied to the hoses will not affect the dP zeroing
function and allows for zeroing of the differential pressure sensor while maintaining connections to the system
under test.
Attaching the Hoses to the Manometer
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. 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 Entrained Air from the Hoses
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. To ensure all the air is bled from the hoses, hold the open end of the Low pressure (blue) hose in an upright
position over 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.
8. Once the liquid is flowing steadily from the Low pressure (blue) hose, turn the valve handle on the manometer
to the MEASURE position.
Performing Pressure Measurements
The HM685 Hydronic Manometer allows for simultaneous and continuous measurement and display of the Highside gauge and Differential pressure. The calculated Low-side gauge pressure is also displayed.
Discrete Pressure Measurements
Taking a discrete pressure measurement allows for measurement and display of a single time-averaged reading
taken over the sampling period as defined by the Log Mode and Log Settings. Discrete measurement values are
stored to the memory (current Test ID) and displayed on-screen for a period of four (4) seconds and then returns
to continuous measurement mode. Press the READ key to initiate.
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