Room sensors QFA2068, QFA2068D, QFA2079 For relative humidity and temperature ● ● ● ● ● A6V11600411_en--_a 2019-08-07 Operating voltage AC 24 V or DC 13.5…35 V Signal output DC 0...10 V / 4…20 mA for temperature and relative humidity Capacitive humidity measurement Accuracy of ±3 % r.h. within comfort range Range of use -15…+50 °C / 0…95 % r.h.
Use QFA2068, QFA2068D and QFA2079 are used in ventilating and air conditioning plants to acquire room ● relative humidity and ● temperature In various places, the sensor is used as a ● control sensor and ● measuring sensor for building automation and control systems or indicating units. Example: ● Offices, hospitals, storage rooms, and so on Type summary Type SSN NO.
Setting element The setting elements are located in the casing. A setting element consists of 6 pins and a jumper. It is used for selecting the required temperature measuring range and for activating the test function. Types with LCD display have a second setting element with 4 pins and a jumper. The different jumper positions have the following meaning: ● For the active temperature measuring range: Jumper in the upper position (R1) = –35...+35 °C, Jumper in the middle position (R2) = 0...
A transformer for safety extra low-voltage (SELV) with separate windings for 100 % duty is required to power the sensor. When sizing and protecting the transformer, the local safety regulations must be complied with. When sizing the transformer, the power consumption of the room sensor must be taken into consideration. For correct wiring of the sensor, refer to the Data Sheets of the devices with which the sensor is used. The permissible line lengths must be considered.
Mode of operation Relative humidity The sensor acquires the relative humidity in the room via its capacitive humidity sensing element whose electrical capacitance changes as a function of the relative humidity. The electronic measuring circuit converts the sensor’s signal to a continuous DC 0...10 V or 4…20 mA signal, which corresponds to 0...100 % relative humidity.
Technical data Power supply Operating voltage AC 24 V ±20 % or DC13.5…35 V (SELV) Frequency 50/60 Hz at AC 24 V External supply line protection Fuse slow max. 10 A or Circuit breaker max. 13 A Characteristic B, C, D according to EN 60898 or Power source with current limitation of max. 10 A Power consumption QFA2068 QFA2068D QFA2079 ≤ 0.4VA ≤0.4VA ≤ 1.4W Functional data of sensor Humidity sensor Range of use 0…95 % r.h. (non-condensing) Measuring range 0…100 % r.h.
Functional data of sensor Time constant 8.5 min (depending on air movement and thermal coupling to the wall) Output signal, linear (terminal U1) DC 0...10 V 0...50 °C / -35...+35 °C / -40…+70 °C max. 1 mA Output signal, linear (terminal I1) 4…20 mA Burden / -40...+70 °C refer to Mode of operation [➙ 5] 0...50 °C / -35...
General Cable lengths for measuring signal Perm. cable lengths Electrical connections Screw terminals for See data sheet for the device handling the signal 1 × 2.5 mm2 or 2 × 1.
Diagrams Internal Diagrams QFA2068 QFA2068D QFA2079 G, G0 Operating voltage AC 24 V (SELV) or DC 13.5...35 V G1, G2 Operating voltage DC 13.5...35 V U1 Signal output DC 0...10 V for relative humidity 0...100 % U2 Signal output DC 0...10 V for temperature range 0...50 °C (R2 = factory setting) -35...+35 °C (R1) or -40…+70 °C (R3) I1 Signal output 4…20 mA for 0...100 % r.h. I2 Signal output 4…20 mA for temperature range 0...50 °C (R2 = factory setting) -35...+35 °C (R1) or -40...
Dimensions Dimensions in mm Issued by Siemens Switzerland Ltd Smart Infrastructure Global Headquarters Theilerstrasse 1a CH-6300 Zug Tel. +41 58 724 2424 www.siemens.com/buildingtechnologies 10 Siemens Smart Infrastructure Document ID A6V11600411_en--_a Edition 2019-08-07 © Siemens Switzerland Ltd, 2019 Technical specifications and availability subject to change without notice.
