ROTRONIC HF7 - Manual (Page 5)

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
© 2009-2011; Rotronic AG E-M-HF7-V1_24
3 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:.