Vaisala HMP5 High-Temperature Humidity and Temperature Probe

Vaisala HMP5 Humidity and Temperature Probe for High Temperatures

The Vaisala HUMICAP® Humidity and Temperature Probe HMP5 is designed for high-temperature industrial processes where accurate humidity measurement, chemical tolerance and long-term stability are essential.

Its long 250 mm stainless-steel probe can be installed through process insulation and positioned directly in the measurement environment. The probe head measures temperatures from −70 to +180 °C, while the cable separates the probe electronics from the hottest part of the process.

The HMP5 is particularly suitable for baking ovens, food and pasta dryers, industrial drying kilns, ceramics production, wood drying and other heated processes. It provides humidity accuracy up to ±0.8% RH and temperature accuracy up to ±0.1 °C under specified conditions.

Built-in Modbus RTU communication allows the HMP5 to operate as a standalone digital transmitter. It can also connect to a Vaisala Indigo transmitter for local display, analog outputs, relays, Ethernet connectivity and additional system-integration options.

Why Choose the Vaisala HMP5?

• High-Temperature Measurement: The probe head operates from −70 to +180 °C for demanding heated industrial processes.
• High Measurement Accuracy: Provides RH accuracy up to ±0.8% RH and temperature accuracy up to ±0.1 °C.
• Long Stainless-Steel Probe: The approximately 250 mm probe facilitates installation through insulated process walls.
• Remote Electronics: The fixed probe cable allows the main probe body to remain outside the highest-temperature measurement zone.
• Sensor Purge: The optional HUMICAP R2C sensor supports chemical purge to reduce the long-term effects of contaminants and cleaning agents.
• Standalone Modbus RTU: Connect the HMP5 directly to a PLC, data-acquisition system or other Modbus master through RS-485.
• Indigo Compatibility: Add display, analog outputs, relays, Ethernet, Modbus TCP and dual-probe capability by selecting the appropriate Indigo transmitter.
• Traceable Calibration: Supplied with a traceable certificate covering six humidity points and one temperature point.
• Industrial Construction: AISI 316L probe construction, sintered stainless-steel filter and IP66-rated probe body support demanding installations.

HMP5 Measurement Performance

Operating Environment

Electrical and Communication Specifications

Mechanical Specifications

Measured and Calculated Parameters

In addition to relative humidity and temperature, the HMP5 calculates multiple humidity parameters for process control, drying analysis and quality monitoring.

• Relative humidity
• Temperature
• Absolute humidity
• Dew point and dew/frost point temperature
• Wet-bulb temperature
• Enthalpy
• Mixing ratio
• Water-vapour pressure
• Water concentration and water mass fraction

Compatible Vaisala Indigo Transmitters

The connection cable between an HMP5 and a compatible Indigo transmitter can be extended to a total distance of up to approximately 30 m using the appropriate Vaisala cabling arrangement.

Standalone HMP5 or HMP5 with an Indigo Transmitter?

View the Vaisala Indigo80 Portable Meter

Common HMP5 Applications

• Industrial Drying: Humidity and temperature measurement for product quality and drying-cycle optimisation.
• Baking Ovens: Monitoring process moisture and temperature in industrial bakery operations.
• Pasta and Food Dryers: Controlling drying conditions to improve uniformity and product quality.
• Ceramics: Measuring kiln and drying-air conditions during moisture removal.
• Wood Drying: Supporting controlled kiln operation and consistent final moisture content.
• Paper and Pulp: Monitoring heated drying processes and exhaust-air conditions.
• Heat-Treatment Processes: Measuring humidity where high temperature and chemical tolerance are required.
• Environmental Chambers: High-temperature humidity measurement within the HMP5 operating limits.

Installation Guidance

• Select an insertion depth that places the sensing section in representative process airflow.
• Keep the probe body and electrical connection outside the highest-temperature zone and below +80 °C.
• Use the optional mounting flange when adjustable insertion depth and a sealed process-wall installation are required.
• Avoid dead zones, direct radiant heating and locations immediately beside heating elements unless those conditions are the intended measurement.
• Route the fixed probe cable away from sharp edges, excessive heat and mechanical stress.
• Confirm that pressure, gas composition and chemical exposure are suitable before installation.
• Allow access for filter inspection, probe removal and calibration.

Calibration and Maintenance

The HMP5 is calibrated and adjusted before delivery and includes a traceable calibration certificate. Calibration and adjustment can be performed using Vaisala Insight PC software, a compatible Indigo transmitter or an Indigo80 handheld indicator.

Calibration frequency should be determined according to the operating temperature, contamination level, process criticality and quality-system requirements. Sensor purge helps maintain stability in chemically challenging environments but does not replace scheduled calibration.

Use Vaisala HMP Probes with Indigo80

Vaisala HMP1, HMP3, HMP4, HMP5, HMP7, HMP8 and HMP9 can be connected to the Vaisala Indigo80 Handheld Indicator using a compatible connection cable.

Which Vaisala HMP Probe Should You Choose?

Vaisala Indigo-compatible HMP probes share the same measurement platform, but their mechanical design and installation method suit different conditions. Use the table below to identify the best starting point for your application.