ROTRONIC HF3 - Manual (Page 18)

E-M-HF3-V1_22
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroFlex HF3 Transmitters and Thermo-
hygrostats: User Guide Instruction Manual
Document Type
Page 18 of 27
Document title
© 2009-2011; Rotronic AG E-M-HF3-V1_22
7 Operation
7.1 Minimum load requirements for the HF33 with voltage outputs
The following requirements apply to any external device or circuit connected to the HF33 transmitter with
voltage outputs:
In the situation where the external device uses an internal pull-up resistor the value of this resistor should
meet the requirements shown below. It is also necessary to add a pull-down resistor RL connected to ground
in order to be able to read 100% of the range of the HF33 voltage output.
HF33 output signal Input resistance RL
0…1V >=1kOhm
0…5V >=5kOhm
0…10V >=10kOhm
HF33 signal VCC R pull-up RL
0…1V 3.3V ≥ 250 kOhm 1 kOhm
HF33 signal VCC R pull-up RL
0…1V 5.0V ≥ 400 kOhm 1 kOhm
0…5V 5.0V ≥ 400 kOhm 5 kOhm
HF33 signal VCC R pull-up RL
0…1V 10.0V ≥ 1 MOhm 1 kOhm
0…5V 10.0V ≥ 1 MOhm 5 kOhm
0…10V 10.0V ≥ 1 MOhm 10 kOhm
RL
GND
HF33
Voltage Output
R Pull-up
RL
GND
VCC
HF33
Voltage Output