Vapor Quality Sensor, Inline

Technical data: HBX 

The Vapor Quality Sensors have a new innovative technology which makes it possible to measure the mix between gas and liquid in a refrigerant from 0% gas to 100 % gas - a measurement no other sensor can provide. It consists of a tube, with metal inserts, where the mix of two phases pass through. The sensor measures the dielectric constant of the fluid, and as two different phases (liquid/gas) has different dielectric constant, the mix between the two, can be calculated. The output of the sensor is the “X” value which has a linear relation to the Volume % of liquid in the gas

The sensor offers very precise measurements and provides instant read-outs of the gas quality, making it useable in most evaporators (plate, pipe, and air evaporators).
The sensor’s microprocessor also functions as a controller, enabling the direct control of a modulating motor valve, thereby bypassing the external controller or the PLC. The controller can be set up with all the parameters that are necessary for regulating a modulating motor valve or a stepper motor valve. The sensor is available with a cable for direct supply to and control of the motor valve, or as a sensor where the signal is sent to the external controller/PLC.

All vapor quality sensors are suitable for controlling both DX, semi flooded and flooded operation.


The straight version called Inline is available from 1” to 2” and the sensor accepts flow in both directions. The pressure loss in the sensor is very low due to the straight flow and smooth internal design. Mounting can be both horizontal and vertical position. The sensor is made in stainless steel and can be butt welded (TIG) or brazed into the system.

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Product features

Measures the volumetric concentration of gas in a gas/liquid mixture
Balanced evaporator control to achieve semi-flooded operation with high heat transfer
Able to control an expansion valve directly with simultaneously analog 4-20mA output to a PLC
Can be used to optimize and control both DX systems and overfeed systems
Instant measurement and analog output
Can be used for all common refrigerants



Optimum efficiency at all loads is obtain by measuring the Vapor Quality in the outlet of the evaporator and use the signal to change the height of the driving head as shown, lower level will minimize the liquid amount  in the evaporator and secure balanced and dynamic evaporation  during part load and thus optimum heat transfer.

The HBX-OVC-ST Vapor Quality control signal (cable out, 4-20mA) is connected to DI 3 (pin 3) on the HBSLC liquid level sensor and used to change the desired set value for the liquid level in the recirculation vessel/separator.


Connection Diagram



Maal HBX Rod 1 tommer O28mm

Maal HBX Rod 3 4 tommer o22mm

Maal HBX Rod 3 4 tommer O22mm L192mm

HBX-Rod style

Maal HBX Inline

HBX-In-line style


Power supply
Voltage24 V AC/DC 
Current consumptionMax 250 mA
Electronic connectionM12, 5 pins
Analouge signal4-20 mA
Alarm outputPNP
Environmental conditions
Ambient temperature-30...+50°C
Refrigerant temperature-60...+80°C
Max. pressure100 bar 
Degree of protectionIP65
Vibrations IEC 68-2-6 (4g) 
Mechanical specifications
Thread connection / welding connectionWelding or brazing
Material liquid partsAISI 304 / PEEK
Material electronic partsGF BLK, Nylon 6 (PA)
SizeSee drawing
WeightSee ordering codes
TypeFront house
EMC testEN 61000-2
5 m cabel with. M12 plugHBxC-M12/5 
Cabel specificationsPUR -5 x 0,34mm2 
LED indicationLED (green, yellow og red)
ConfigurationWith PC tool

Ordering code

Pipe diameterStainless steelOrdering code
DN 25 (1”)Available
DN 40 (1 1/2”)Available
DN 50 (2”)Available
Vapor quality sensors come in numerous variants - all customized to the application. An order contains a mechanical part and an electronic part programmed to the order. Before ordering you need to consider:
1) The dimension and steel type for the mechanical part. (see table above)
2) The configuration and specification of the electronic part.
To make the right configuration of the sensor, please choose the functions and specifications you need for the electronic part:
Control function: (More than one function is possible)
☐ Analog output only 4-20 mA to PLC/main controller
☐ Control of stepper motor valve e.g. Carel E2V
☐ Control of PVM valve e.g. Danfoss AKV
☐ Control of motor valve e.g. Siemens MVS661 and Danfoss ICM
Refrigerant: (Only on selection)
☐ NH3
☐ CO2
☐ Other please specify
Application: (More than one function is possible)
☐ Direct expansion DX
☐ Overfeed system/flooded/pump circulation
☐ Compressor protection
☐ Leakage protection in ammonia CO2 cascade (ammonia carbamate)
☐ Other please specify
Other functions: (More than one function is possible)
☐ Remote setting of setpoint*
☐ USB cable
* Makes it possible to control the vapor quality (X) setpoint dynamically in the sensor used for controlling an expansion valve directly. The remote setting must be set from a PLC.

To order: Please fill out theHBX Vapor Quality Sensor Ordering Form and attach it in an e-mail to


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