Data Sheet for Product
3/10
Siem ens Indoor air quality sensors QPA10.., QPA20.. CE1N1961en
Building Technologies 2018-05-01
Symaro
TM
air quality sensors determine the mixed gas concentration (VOC) using met-
al-oxide semiconductor sensing elements. The sensors measure precisely at all times
and with no maintenance and recalibration required thanks to an integrated compensa-
tion mechanism, saving service costs.
The sensor provides a DC 0...10 V or DC 0...5 V or 4...20 mA output signal proportion-
ate to the VOC content of the ambient air.
X1
% VOC
10
8
6
4
2
0
0
20
40
50
80
1
00
1961D03_0
1
[mA] [V]
20
16.8
13.6
10.4
7.2
4
Select the time constant for VOC measurement by limiting the maximum slew rate for
the VOC signal. The jumper X130 (measuring range) fine tunes the time constant for
VOC ventilation demand.
The center position (R2) produces a normal slew rate of max. 10% change to the VOC
signal per minute (factory setting). The other 2 position reduce (R1, 2.5% VOC/min) or
increase (R3, 40% VOC/min) the maximum slew rate. A smaller slew rate (R1) filters
out short-term VOC concentration peaks, e.g. caused by a highly perfumed person
passing by. The sensor reacts immediately and quickly to changes in VOC concentra-
tion at the higher slew rate (R3).
Time constant t
63
selected by jumper X130 corresponds to <13 min (R1), <3.5 min (R2),
or <1 min (R3) for a sudden change to 50% VOC.
The sensor acquires and evaluates the CO
2
/ VOC concentration and transforms it to a
ventilation demand signal.
It represents the result of maximum selection of the CO
2
measuring signal and the fil-
tered VOC measuring signal. With maximum selection, the 2 demand signals are com-
pared and provided as common air quality demand.
The ventilation demand signal is provided via output X2 as a DC 0…10 V or
DC 0...5 V or 4...20 mA signal to be supplied to the ventilation controller.
X2
Max
10
8
6
4
2
0
0
400
800
1200
1600
2000
1961D02_0
1
[ppm CO ]
2
0
20
40
50
80
1
00
[% VOC]
[mA] [V]
20
16.8
13.6
10.4
7.2
4
The sensor acquires the relative humidity in the room with a capacitive humidity sens-
ing element whose capacitance changes as a function of relative humidity.
An electronic measuring circuit converts the signal from the sensing element to a con-
tinuous DC 0...10 V or DC 0...5 V or 4...20 mA signal, corresponding to a relative hu-
midity range of 0...100 %.
VOC concentration
(QPA1000)
Diagram VOC
(Output X1)
Time constant
"VOC signal"
CO
2
/VOC concentration
(QPA2002 and QPA2002D)
Ventilation demand
diagram (output X2)
Relative humidity
(QPA2062 and
QPA2062D)