User Manual

E-M-HF4-V1_22

Rotronic AG

Bassersdorf, Switzerland

Document code

Unit

HygroFlex HF4 Humidity Temperature

Transmitters: User Guide

Instruction Manual

Document Type

Page

3 of 29

Document title

Applicability:

This manual applies to all instruments of the HF4 series with firmware version 1.x, where 1.x can be 1.0, 1.1,

etc. Changes to the last digit of the version number reflect minor firmware changes that do not affect the

manner in which the instrument should be operated.

1 Overview

The HF4 transmitter measures temperature, relative humidity and the dew or frost point. The HF4 series is

designed for fixed installation in HVAC and light industrial applications where a high measurement accuracy is

required at conditions within the range of 0 to 100 %RH and -50 to 100 C (-58 to 212 F). The electronics

operating range is limited to -40…60 °C (-10…60°C with the optional LC display).

The HF4 features well proven sensors and a robust housing. Digital signal processing ensures consistent

product performance and also facilitates the task of field maintenance with features such as potentiometer

free – digital calibration.

Based on the ROTRONIC AirChip 3000 digital technology the HF4 series offers the following functions:

User configurable settings

Calculation of the dew or frost point

Humidity temperature calibration and adjustment

Simulator mode

Automatic humidity sensor test and drift compensation

Fail safe mode

Data recording

The ability for the user to easily update the AirChip 3000 firmware means that instruments of the HF4 series

can be kept up-to-date regarding any future functionality improvement.

HF4 transmitters with analog output signals: two types of electronic circuit are available: HF42: 2-wire,

loop powered (4…20 mA current signal) and HF43: 3-wire (voltage or current signal). Both circuit types

provide linear analog outputs signals for transmission over a length of cable to a remote display, recorder,

controller or data processing unit and can be used to measure humidity only, temperature only or both

parameters.

HF4 transmitters with digital output: the HF45 is available with the following digital interface options: RS-

485, USB + RS-485 or Ethernet (TCP/IP) + RS-485. Use of a digital interface allows the simultaneous reading

of relative humidity, temperature and calculated parameter. The communication protocol used by the RS-485

interface offers several options that can be configured by the user. This includes a Modbus compatible

protocol.