HX402W Temp. RH Signal Conditioner with LCD

Supported Applications

The HX400 Series is a programmable, 2-wire loop-powered field transmitter that provides remote and on-site monitoring of relative humidity and temperature. Built around a digital polymer capacitive humidity sensor and a silicon temperature sensor, it converts, indicates, transmits, and switches these measurements as linearized, temperature-compensated 4 to 20 mA signals to remote receivers.

Designed for environmental air monitoring and building systems, the HX400 suits HVAC and ventilation control, clean-room and laboratory air, storage and process rooms, and other indoor spaces where humidity and temperature must be tracked and controlled. It works with air and neutral gases, and a front three-pushbutton keypad with dual high-bright 3-digit LED indicators (green for humidity, red for temperature) makes on-site setup and reading straightforward.

The transmitter is intended for non-aggressive environments and indoor room use; it is not recommended under condensation or water-aerosol conditions, which can damage the sensor or dramatically increase response time. Each unit is CE marked and manufactured to ISO 9001 quality standards, with optional NIST-traceable calibration available.

Operating Conditions & Performance

Without field calibration, the HX400 measures relative humidity from 0 to 100% to ±2%, temperature to ±0.5°C (0.9°F), and dew point to ±2°C (3.6°F). The sensing probe operates from -40 to 100°C (-40 to 212°F), while the electronics device works from -20 to 70°C (-4 to 158°F). Key performance figures include:

• Repeatability: ±1% RH, ±0.1°C
• Display resolution: 0.1% RH, 0.1°C (temperature < 100°C)
• Response: 10 seconds (relative humidity); 30 seconds maximum (temperature)
• Output current accuracy: ±0.02 mA on 4 to 20 mA, both channels, at 23°C

The transmitter runs on 12 to 32 Vdc dual 4 to 20 mA loop current and is reverse-polarity protected, specified at Vloop = 24 Vdc, Tamb = 23 ±2°C, and Rload = 250 Ω. A dual galvanically isolated solid-state output is rated 15 mA maximum, 40 Vdc maximum. The sensor cap uses a 0.05 mm stainless steel wire mesh filter, and the probe is 15.5 mm (0.61") in diameter. The electronics carry a NEMA 4 (IP65) rating while the sensing probe is rated IP40. Each unit weighs 250 g (8.8 oz) and measures 110 W x 80 L x 56 mm D (4.3 x 3.2 x 2.2").

Configuration Options

The six models divide along two dimensions: measured parameters and mounting style. The HX401 models are relative humidity transmitters, while the HX402 models add temperature, transmitting both RH and temperature. Note that an HX402 will be damaged if only Ch #1 is powered, so both channels must be energized.

Each function is available in three mounting configurations to match the installation:

• W — Wall mount: for room and wall-surface monitoring
• R — Remote probe: for locating the sensor away from the electronics
• D — Duct mount: for in-duct air monitoring

All variants share the same 4 to 20 mA dual-channel output, digital capacitive sensing, and front-panel LED indication; only the measured parameters and physical mounting differ.

Key Product Differences

The series comprises six transmitters, three relative-humidity-only models and three combined RH-and-temperature models:

• HX401W — Wall mount relative humidity transmitter
• HX401R — Remote probe relative humidity transmitter
• HX401D — Duct mount relative humidity transmitter
• HX402W — Wall mount RH and temperature transmitter
• HX402R — Remote probe RH and temperature transmitter
• HX402D — Duct mount RH and temperature transmitter

Supporting accessories include CAL-3-HU NIST-traceable calibration, the RHCN-7001 RH controller, regulated power supplies (PSR-24S, PSR-24L, and the European-plug PSR-24L-230), the PSU-93 unregulated power supply, and the TX4-100 4-conductor shielded transmitter cable.