hygrotest 650 – humidity transmitter

  • hygrotest 650 –  humidity transmitter
  • hygrotest 650 –  humidity transmitter
  • hygrotest 650 –  humidity transmitter
  • hygrotest 650 –  humidity transmitter
The high-performance humidity transmitter for air conditioning and processes
Part #: 0555 0650


The hygrotest was developed specially for humidity measurement in air conditioning and process engineering. This sophisticated measurement is performed by the Testo humidity sensor with the much valued and well-known long-term stability. The result of the development - the culmination of many years of work - and the experience of the hygrotest on the market is a measuring range of 0 to 100 % RH and a standardized measuring accuracy of +/-2 % RH (optional +/-1 % RH) for the hygrotest 650. The hygrotest 650 HP is ideal for high-humidity applications thanks to its innovative heated technology and ensures fast reaction speeds of the sensor and a long life under extreme humidity conditions (close to the 100 % mark). The hygrotest 650 with the H8/H9 display versions is specially designed for humidity measurement in an H2O2 environment (sterilization applications). It indicates the calculated variables, the mixture humidity or mixture dewpoint. Two analog outputs that can be scaled as required, plus an optional relay, or an RS 485 digital signal output are available for outputting the relative humidity, temperature, absolute humidity, psychrometer temperature or the degree of humidity. In addition, the hygrotest stands out for its compact and robust design, witness the metal housing of the hygrotest 650/650 HP.
  • Accuracy of up to ±2 % RH (optional ±1 % RH)
  • Option of wall, duct or probe version
  • hygrotest 650 HP heated version for constant high humidity ranges (The Testo humidity sensor is heated on the back. This creates a microclimate around the sensor with a lower relative humidity. The reaction speed is noticeably better and the risk of the sensor corroding is reduced.)
  • G8 sensor cap and H8/H9 display version for H2O2 environment (including 3rd analog output for calculated mixture humidity/mixture dewpoint variable)
  • Extremely easy to check and adjust on-site using the testo 400/650 reference measuring instruments or reusable saline solutions
  • 2 analog outputs are standard with the option of digital outputs:
    • RS485 output for online monitoring
    • 4 switch outputs
  • All the standard types of signals (current/voltage) are available for the analog outputs. The signal type must be chosen on ordering)
  • There is a choice of various line and probe lengths
  • Probes and sensors are heat resistant up to temperatures of +180 °C
  • User-friendly, password-protected user menu with control keys on outside (if optional display is installed):
    • Modification of physical size and scaling
    • Requesting of min./max. values
    • Testing of analog and switch signal
    • Modification of limit values and hysteresis
    • 2-point adjustment
    • Reset
  • A robust, easy-to-clean metal housing is available as an option to protect against environmental influences
  • A range of humidity variables can be calculated and output using the integrated Mollier diagram:
    • Dewpoint
    • Absolute humidity
    • Specific humidity

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