Passive humidity transmitter for 4...20 mA current loops

HD49

Passive humidity transmitter for 4...20 mA current loops, measuring relative humidity, temperature or dew point, with 12...40 Vdc supply, IP65 housing and flexible wall, duct or remote probes.
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Introduction

Current-loop systems need transmitters that integrate cleanly and keep environmental data dependable over time. HD49 passive transmitters measure relative humidity, temperature and calculated dew point for HVAC/BEMS, ventilation ducts, cleanrooms, museums, pharmaceutical areas, public spaces, greenhouses and industrial or civil facilities.
 
The series is built around 2-wire 4...20 mA current loop integration, making it suitable for remote displays, recorders and PLCs. A temperature-compensated capacitive RH sensor supports long-term measurement stability, while factory calibration allows the transmitter to be used without initial adjustment.
 
Installation can be matched to the site. Choose vertical wall probes, horizontal duct probes or remote probes with 2, 5 or 10 m cable, plus 135 mm or 335 mm stem lengths where applicable. Standard versions cover -20...+80 °C, selected TC and TO versions extend to -40...+150 °C, and the IP65 ABS housing with protected probe filters supports demanding indoor environments.

Loop-ready design
2-wire 4...20 mA output integrates with displays, recorders and PLCs.
Flexible installation
Wall, duct and remote probes cover common HVAC and BEMS mounting points.
Wide temperature use
Selected TC and TO versions extend the range from -40...+150 °C.
Ready to install
Factory calibration allows immediate use without initial adjustment.

Features

Measured quantities

Models are available for relative humidity, temperature, relative humidity with temperature, or dew point with temperature.

Passive current loop

The transmitter operates with a 2-wire 4...20 mA output and 12...40 Vdc power supply.

Probe configurations

The series includes fixed vertical wall probes, fixed horizontal duct probes and remote probes with cable lengths of 2, 5 or 10 m.

Sensor technology

Relative humidity is measured with a capacitive sensor, while temperature is measured with NTC or Pt100 depending on version.

Probe protection

Probe filters use PBT with stainless steel grid as standard, or 20 µm PTFE for extended range versions.

Configuration and calibration

Relative humidity calibration can be performed with saturated salt solutions and HD48TCAL software.

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