Choose the right humidity transmitter for your application

how to choose most suitable humidity transmitter


Measuring humidity is important in almost every application to ensure high quality and safety in living and production:

  • HVAC (Heating, Ventilation, and Air Conditioning) Systems: Humidity transmitters are used to control indoor humidity levels, ensuring comfort, and preventing issues like mold growth.
  • Pharmaceutical and Medical Storage: Maintaining specific humidity levels is critical for storing medication and sensitive medical equipment.
  • Food and Beverage Processing: Humidity control helps preserve product quality and shelf life in food production.
  • Museums and Art Galleries: Controlling humidity is essential for preserving valuable artwork and historical artifacts.
  • Cleanrooms: Precise humidity control is crucial for maintaining product quality in semiconductor manufacturing and pharmaceutical production.
  • Greenhouses: Monitoring and controlling humidity levels in greenhouses helps optimize plant growth and yields.
  • Data Centers: Humidity control is vital for preventing electrostatic discharge and other issues in data centers.
  • Laboratories: Maintaining specific humidity levels is necessary for accurate experiments and testing.
  • Industrial Processes: Humidity control is essential for product quality and consistency in many manufacturing processes.
  • Agricultural and Livestock Facilities: Proper humidity control can enhance animal comfort and health.

Therefore, it is important to choose the right transmitter to comply with regulations and achieve the benefits of humidity measurement. But which one fits best for my application?

Questions that Need to be Answered to Choose the Correct Measurement Equipment

As described in our Blog “Understanding Fixed vs. Interchangeable Probe Humidity Transmitters”, key decision-making questions need to be considered. If you have answered those questions, you are on track to finding the right transmitter.

In the following section we are going to identify the typical applications for the HygroFlex transmitter range:

relative humidity transmitter

Humidity & Temperature Transmitter Rotronic HF1:

The HF1 is the entry-level transmitter in the HygroFlex product family containing the reliable and long-term stable Rotronic Humidity IN-1 Sensor. There is a duct (D), wall (W) and space (S) version of the transmitter. They all have a fixed probe and can measure Humidity and Temperature with (for most applications) a satisfying accuracy of

Type W & D: ± 2% rh, ± 0.3 K

Type S: ± 3% rh, ± 0.1 K

Furthermore, the HF1 provides a 2-point humidity adjustment using the HygroSoft. For every application in which the accuracy and low maintenance cost are acceptable, the HF1 is the right transmitter to choose, such as HVAC, food industries, printing and paper industries, indoor swimming pools, museums, greenhouses, offices and many more...

Humidity & Temperature Transmitters Rotronic HF3 and HF4:

Compared to the HF1, the HF3 and HF4 have a wider temperature operating range, which can be used in applications where more challenging environmental conditions prevail. Both can calculate dew and frost points and their output can be changed from output voltage to current and vice versa. The outputs are completely user-scalable using the HygroSoft Software. In addition, the HF4 has buttons that enable the user to configure it directly on the spot and a stunning accuracy of ± 1% rh, ± 0.2 K.

Humidity & Temperature Transmitter Rotronic HF5A

The HF5A Transmitter is the high-end device of the HygroFlex family. In addition to the HF4, it can calculate all the psychometric parameters and has an ethernet connector for RO-ASCII communication. Furthermore, it comes with an interchangeable probe. This gives the user the best possibility in case of configuration, flexibility and calibration services. The HF5A Humidity & Temperature Transmitter, combined with the high-accuracy HC2A Humidity & Temperature Probe series, make it suitable for all special industrial applications, with no downtime!

Example application:

Application HF5A, in combination with extension cable and HC2A
Pressurized Pipe up to 100bar HF5A & HC2A-IE
Sterilization with H2O2 HF5A & E2-02A & HC2A-S-HH
Monitoring food process HF5A & E2-02A-M & HC2A-SM
Industrial process with high temperature HF5A & HC2A-IM305-M

To round off the application range, the HF5A is also available for ATEX applications and with galvanic separation.

Humidity & Temperature Transmitters Rotronic DT722 / HF73A

The DT722 and HF7 are specially designed to be used in harsh conditions (industrial environments and outdoors) and can show high temperature resistance of the housing. The DT722 has a full steel housing and the HF73A an aluminium housing. The special feature of the DT722 is that it can be built completely analog, i.e. there are no digital components, which is beneficial for security applications.

Differential Pressure, Humidity & Temperature Transmitters Rotronic PF4 / PF5

Both the PF4 and PF5 are high-end devices which, in addition to measuring humidity and temperature, can measure a third parameter – the differential pressure. This makes it suitable for clean room, food and pharma applications. The differences between PF4 and PF5 lie in the measurement methods:

  • Membrane Sensor (PF5): Has the advantage that there is no cross contamination, and no ambient pressure compensation is needed. On the other hand, it has a low overload pressure and is more sensitive to vibrations. A membrane sensor also requires a regular zero-point adjustment. Our devices have a valve built in for this purpose
  • Flow Sensor (PF4): Has the advantage of a higher overload pressure and is not sensitive to vibrations. Instead, it needs ambient pressure compensation and, due to the measurement method, it has cross contamination.

The interchangeable HC2A series can be connected to the PF4 / PF5 to measure humidity and temperature or, alternatively, an external PT100 to measure temperature.

relative humidity transmitter

The PF4 / PF5 are equipped with all possible features, for example Modbus on RJ45 or RS485, Relay or Analog Input. The full features range can be seen in the following diagram:

relative humidity transmitter

Practical Table Supporting You to Choose the Most Suitable Transmitter

To give the user a better overview of the technical features, configuration possibilities and to summarize the differences, we have created a practical lists of Rotronic Transmitters:

Humidity & Temperature Transmitter Guide

relative humidity transmitter
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Differential Pressure, Humidity & Temperature Transmitter Guide

relative humidity transmitter
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Related Product Information
Probes and Sensors for Measurement of Relative Humidity
Transmitters for Humidity Measurement
Understanding Fixed vs. Interchangeable Probe Humidity Transmitters

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