General description, Power supply, Measured parameters – ROTRONIC HF7 User Manual

Page 5: Calculated parameters, Analog output signals, E-m-hf7-v1_24, 3general description

E-M-HF7-V1_24

Rotronic AG
Bassersdorf, Switzerland

Document code

Unit

HygroFlex HF7 Humidity Temperature
Transmitters: User Guide

Instruction Manual

Document Type

Page 5 of 23

Document title

General description

3.1 Power supply

Depending on the circuit type, the HF7 requires the following power supply:

a) HF72 (2-

wire, loop powered): 10…28 VDC - depending on the load connected to the output(s). The

minimum supply voltage can be determined as follows:

V min = 10 V + (0.02 x Load*) *Load resistance in ohms.

For the maximum load of 500 , the minimum supply voltage is 10 + (0.02 x 500) = 20 VDC. With both
output circuits closed, the maximum current consumption is 40 mA.

b) HF73 (3-wire with analog outputs): 15 to 40 VDC (see note below) or 12 to 28 VAC. With both output

circuits closed, the maximum current consumption is 50 mA.

Note: depending on the type of output signal, the HF73 will operate with the following minimum voltage

0…1 V outputs:

5 VDC or 5 VAC

0…5 V outputs:

10 VDC or 8 VAC

0…10 V outputs:

15 VDC or 12 VAC

0…20 mA or 4 …20 mA outputs:

6 VDC or 5 VAC with 0 load

15 VDC or 12 VAC with 500 load

3.2 Measured parameters

The HF7 measures relative humidity with a ROTRONIC Hygromer

IN1 capacitive sensor and temperature

with a Pt100 RTD.

3.3 Calculated parameters

Using the ROTRONIC HW4 software, the HF7 can be configured by the user to calculate either the dew point
or the frost point.

3.4 Analog output signals

HF72 and HF73

With the ROTRONIC HW4 software any of the two analog output signals can be made to correspond to one of
the following:

Relative humidity
Temperature
Dew or frost point

Any output can also be disabled.

The scale of each analog output can be set within the numerical limits of -999.99 and 9999.99.

The D/A converters used to generate the analog output signals feature a 16-bit resolution.

The D/A converters used to generate the analog output signals feature a 16-bit resolution and exhibit a small
positive offset at the bottom of the signal range as indicated below:.