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The flow tester 3925-0160

The flow meter operates on the thermodynamic principle.
The instrument uses the linear relationship between the flow rate and the energy carried along. At a thin stainless steel pipe two thermal resistance elements are mounted. A part of the air or gas flow passes through this bypass and is heated with constant power by two heating elements. Due to thermal transfer the two temperatures drift apart. The difference between the two temperatures is directly proportional to the air mass flow.

The advantages of the flow tester

In the industry flow test is used quite often. Pipe structures (like exhaust systems), valves, fittings or many other parts can be checked with a flow tester.
Measuring the mass flow directly is very precise. In addition a wide choice of measuring ranges is available and the wide measuring span (1:50) makes our flow tester applicable for most diverse applications.
Different methods can be used to determine the mass flow. Our flow tester 3925-0160 uses a thermal mass flow meter. Contrary to the volumetric flow meters no additional sensors for temperature and pressure are needed. So the installation of our flow tester is higly simple and makes the quality check of your products as easy as possible.

The functionality of the flow tester

Automation of the workplace nowadays have to be realized even in quality assurance. To test production parts for flow, it is therefore necessary to integrate the flow test in the manufacturing process.
Important features of the FLOW TESTER 3925-0160 are:

  • automatic control cycle
  • storage of test programs
  • contamination free test
  • reproducible measuring results
  • short cycle times with high accuracy
  • unambiguous results
  • measured value in ml/min etc.
  • programmable test pressures and test times to suit to the production of many different components
  • user friendly operation with interactive user guidance
  • modular design concept for ease of maintenance and service

Operating principle

A high-precision thermal mass flow meter with high sensitivity is used as measuring sensor. This unit consists of a measuring tube and an exchangeable bypass which determines the measuring range.
The design of the measuring tube and the bypass ensures a laminar flow inside.

A heating coil is located in the middle of the measuring pipe. Temperature sensors are placed in equidistance on both sides of the heating. Without a gas flow both sensors register the same temperature. Any gas flow leads to a temperature difference between the sensors which is directly proportional to the mass flow on the inside of the pipe.


Programming of the control and test parameters is menu guided - no special knowledge is required. The test parameters are stored in the program register and can be recalled as required. Different selectable languages are available.

A write-protect key switch ensures data security. Data can be read but not modified by the operator.
Machine control systems are able to communicate with the leak tester via the standard parallel (discrete I/O) interface or various other optional interfaces. 
A serial interface is available to connect the leak tester with a computer or printer. Other optional protocols are available (see technical data).


Pneumatic System

  • microprocessor controlled electronic pressure regulation for filling and test pressure
  • thermal mass flow meter with with overload protection
  • function monitoring


Electronic System

  • modular designed processor system
  • battery-buffered RAM for data protection
  • alphanumeric keypad
  • 5 inch color display
  • write-protect key switch to prevent unauthorized program changes
  • error messages as plain text
  • menu guided programming and adjustment of parameters
  • various interface ports to communicate with control systems

Technical data


Program storage:   Battery buffered RAM
Keypad:   Alphanumeric
Display:   5 inch color liquid crystal display, 320x240 pixel
Measuring sensor:   Thermal mass flow meter PN100
Measuring range:   0 ... 50; 100; 200; 500 ml/min, 
0 ... 1000; 2000 ml/min,
0 ... 5; 10; 20; 50; 100 l/min,
others on request
Resoluton:   high resolution SigmaDelta A/D converter
1 converter per channel
Measuring units:   ml/min, l/min and m³/h
Test programs:   99
Filling and test pressure:   -1.0 ... 0 bar/g; -0.7 ... -0.1 bar/g
0.1 ... 1.0 bar/g; 0.15 ... 2.5 bar/g
0.2 ... 6.0 bar/g; 0.5 ... 10.0 bar/g
0.5 ... 12 bar/g
others on request
Test parameters:   Filling pressure
Test pressure
Filling time 0.1 ... 999.9 sec 
Compensation time 0.1 ... 999.9 sec
Measuring time 0.1 ... 999.9 sec
Lower tolerance limit LT
Upper tolerance limit UT
No. of consecutive rejects
Write protection:   Key switch
Status indicator:   Lower tolerance
Upper tolerance
Test data storage:   Up to 8,000 tests
(internal battery buffered RAM)
for larger data storage use front connection for external USB memory stick
optional: larger internal memory is available

1 parallel control I/O port

Control inputs:
24 V DC; 500 mA
1 Bit Automatic

1 Bit Device ready
1 Bit Start
1 Bit Leak simulation
1 Bit Flooding (static test)
8 Bit Program Select
1 Bit Abort

    Control outputs
24 V DC; 500 mA
short circuit proof 
1 Bit Ready to operate
1 Bit Ready to test
1 Bit Error
1 Bit O.K.
1 Bit UT (Upper Tolerance)
1 Bit LT (Lower Tolerance)
1 Bit Measuring

1x Serial Port RS 232 or USB 2.0 for transfer of parameters, test results and counter readings

1x front USB 2.0 for transfer of parameters, test results and counter readings

Optional Bus Interfaces:
FastEthernet, Profibus, Profinet, others on request

Housing:   19 inch rack mount case, 3 HU
Dimensions:   165 x 590 x 420 mm (H x W x D)
Power supply:   100/240 V, 50 ... 60 Hz
Power consumption:   Approx. 100 VA
Air supply:   Test air: 1.5 bar > test pressure
Control air: max. 10 bar/g
filtered, dry and oil free
Pneumatic ports:   Air supply G1/4",
optional test medium port G1/4"
Test port G 1/8",
Venting: G 1/4"
Weight:   Approx. 15 kg
Standard accessories:   Power cord, length approx. 2.5 m,
Spare key for write protection,
Operating manual
Order-No.:   Flow Tester 3925-0160
    Specifications and technical data are subject to change without notice



HeMaTech Prüftechnik GmbH & Co. KG
Siemensstr. 7
D-71409 Schwaikheim


Calibration Service for
Measurand Pressure




Tel.: +49 (0) 71 95-13 69 0
Fax: +49 (0) 71 95-13 69 29


Certified according to
ISO 9001:2015


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