
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. 
-2- 

Performing Flow Measurements 
A calculated value determined from the differential pressure and user entered values for the 
valve flow coefficient (Cv or Kv) and fluid specific gravity. 
The valve flow coefficient is indicated as Cv (Kv) on the manometer display. The Cv (Kv)  
value of the measured valve must be known in order to obtain meaningful flow readings. The 
Cv (Kv) value can be temporarily edited within the Flow Measurement screen by pressing the 
▲ or ▼ key to enter an edit mode. Use the ▲ or ▼ keys to change the value. Press ESC to  
leave the edit mode. 
Temperature
Current 
Test ID
Current Cv (Kv) 
Factor Name
Differential
Pressure
Battery Status or 
Power Input Type
Cv/Kv Value
The manometer makes and displays continuous differential pressure measurements, calculates and displays 
continuous flow readings, and allows for discrete data storage to the memory when in the Flow measurement 
screen. 
Discrete Flow Measurements 
Taking a discrete flow 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 pressure or flow measurement 
values are stored to the memory (current Test ID) and displayed on-screen for a period of 4 seconds and then 
returns to continuous measurement mode. Press the READ key to initiate. 
Performing Temperature Measurements 
The accessory temperature probes are optional for the HM685 Hydronic Manometer and can be connected to the 
3-pin mating connector located on the right-hand side of the manometer. The unit of measurement for 
temperature (°F or °C) is driven by the differential pressure measurement: 
Differential pressure in psi, inH2O, ftH2O, or inHg → temperature in °F 
Differential pressure in kPa, mH2O, mmHg, or bar → temperature in °C 
Menu Items 
Pressing the  key from either the Pressure or Flow Measurement screens accesses 
the Main Menu, select a menu item or accept changes. Use the arrow ▲▼ ◄► keys 
to navigate through menu items and change selected items. 
Flow Setup 
Use Flow Setup to set values for key factors that impact measured flow values. 
-3- 

USA  Tel: +1 800 874 2811  
UK  Tel: +44 149 4 459200  
France  Tel: +33 1 41 19 21 99  
Germany Tel: +49 241 523030 
India  Tel: +91 80 67877200  
China  Tel: +86 10 8219 7688  
Singapore Tel: +65 6595 6388 
Data Logging 
Samples are automatically logged to memory at the end of the sampling period. To 
start logging, press the Read key. 
Logging starts by press the Read key. The instrument continues logging until the Esc 
key is pressed. 
Readings start by pressing the Read key. The instrument continues taking samples 
until the time set in “Sample Time” elapses or the Esc key is pressed. 
Access the Data Logging Menu by pressing the DATA key from either the Pressure or Flow Measurement 
screens or from the Main Menu. 
Log Mode: HM685 programmable logging formats: 
Log Settings: defines the period the manometer will log sample readings. When the Log Mode is set to Cont-
Time, this setting is also used to define the length of the test in hh:mm:ss. 
Choose Test: choose the Test where the samples (readings) will be stored.  
Name Test: customize the Test ID name of the selected test using 10 characters maximum.  
View Data: choose the data to review.  
Delete Data: delete discrete samples, an entire Test ID, or all data stored.  
Memory: displays the total memory available 
Calculations 
The Calculations Menu is accessed by pressing the CALC key from either the 
Pressure or Flow Measurement screens. 
Brake Power: determines pump brake power using flow, delta P and pump efficiency  
Heat Flow: determines heat flow using temperature, flow, specific heat and gravity  
Calc Cv/Kv: calculates Cv or Kv based on flow and differential pressure  
Pump Law Impeller Diameter:  allows for determination of required pump 
impeller size 
Pump Law Delta P: determines required pump pressure drop using flow and delta P inputs  
Pump Law Brake Power: determines pump brake power based upon the following affinity law: Pump brake 
power varies as the cube of flow 
Settings 
The Settings menu allows customization of the 
instrument display. 
TSI Incorporated – Visit our website www.tsi.com for more information. 
P/N 6006776 Rev C  ©2015 TSI Incorporated  Printed in U.S.A.