Rotronic HygroPalm HP21

The HP21 is the ideal instrument for humidity and temperature measurements in simple applications. The integrated HC2 probe guarantees measuring results of the highest accuracy.


The HP21 is a highly accurate handheld indicator that displays relative humidity, temperature and dew or frost point temperature. The HP21 is perfect for spot checking HVAC installations, manufacturing or storage areas and any ambient air measurement within the temperature range of -10 to 60°C (14 to 140 °F). The HP21 is designed to meet a wide range of user requirements from the most basic applications to the most demanding applications.

The HP21 indicator offers an extensive set of settings and functions that can be configured and enabled by the user with the ROTRONIC HW4 software. In spite of its high end design, the HP21 is ideal even as a simple humidity and temperature indicator.

Mobile inspection and random tests in HVAC, the pharmaceutical industry and building management systems


  • Range of application -10…60 °C / 0…100 %rh
  • Accuracy at 23°C ±5 K: 1 %rh, 0.2 K
  • Adjusted at 23 °C and 10, 35, 80 %rh
  • Service interface (UART)
  • Calculation of dew and frost point


Dimensions268 x 72 x 30 mm
Operating range-10…60 °C / 0…100 %rh
Accuracy at 23 ±5 °C±1.0 %rh / ±0.2 K
Accuracy w. adjustment profile “standard”at 23 °C / 10, 35, 80 %rh ± 1.0 %rh / ± 0.2 K
Measuring range with integrated probe-10…60 °C / 0…100 %rh
Power supply / Power consumption9 V battery, power supply
4 mA consumption without lighting
Long-term stability<1 %rh / year
Humidity sensorHygromer IN-1
Temperature sensorPT100 1/3 DIN Class B
Probe protectionPolycarbonate plastic cage, black
Response time t 63<3 sec.
Allowed wind speed40 m/s, with filter
Psychrometric calculationsDew or frost point
Calibration / adjustmentwith keypad
Reproducibility Airchip<0.02 %rh / 0.01 K
Initialisation timeTypically <3 sec.
Measurement interval2 seconds
Display typeGraphic display. Display freely configurable.
Backlightwith Backlight
Alarm indicatorsYes
Battery indicatorLow Batt. Display
Exploitation softwareROTRONIC HW4
Menu guidanceYes
Trend indicatorYes
Probe adjustment by softwareYes, with service cable
Firmware updateWith internet and HW4 software
User informationfrom Software HW4 (devicemanager)
Data processing via HW4Graphics, statistics, analysis, qualification, etc.
Device Protection by passwordYes
Service InterfaceMini USB (UART)
Max. cable lengthUp to 5 m with passive cable. Up to 100 m with active cable.
Enclosure materialABS
IP protection ratingIP40
Fire protection classComplies UL94-HB
FDA/GAMP compatibilityFDA 21 CFR Part 11 and GAMP compatible


Datasheet (PDF)

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