Uv Flame Detectors Qra2 / Qra4 / Qra10 - Siemens LMV37.4 Series Basic Documentation

Measuring circuit for
detector current
measurement
Building Technologies

4.4.2 UV flame detectors QRA2 / QRA4 / QRA10

Caution!
If QRA2-UV tubes / QRA4-UV tubes / QRA10-UV tubes are used for flame
supervision on the LMV37.4, it must be ensured that the LMV37.4 is
permanently connected to power (EN 298), thus enabling the LMV37.4 to detect
flame detector failures during startup and shutdown.
Generally, the LMV37.4 works with QRA flame detectors in intermittent
operation.
For technical data, refer to Data Sheet N7712 covering QRA2 / QRA10 UV flame
detector!
For technical data, refer to Data Sheet N7711 covering QRA4 UV flame detector!
Operating voltage
Required detector current in operation
Possible detector current in operation
Permissible length of flame detector cable
normal cable (laid separately)
Threshold values when flame is supervised by QRA:
 Start prevention (extraneous light)
 Operation
UV flame detector QRA
QRA...
Figure 7: Measuring circuit QRA
Legend
A Incidence of light
C Electrolytic capacitor 100...470 µF; DC 10...25 V
Microammeter Ri max. 5000 
M
Warning!

Input QRA is not short-circuit-proof!
Short-circuits of X10-06 pin 2 against earth can destroy the QRA input

Simultaneous operation of QRA and ionization probe is not permitted!
Basic documentation LMV37.4...
4 Technical Data
Max. 350 V peak
Min. 30 µA
When the more sensitive flame
supervision is activated, the required
detector current is halved (see chapter
Flame detection sensitivity).
Max. 600 µA
Max. 6 m
Intensity of flame (parameter 954) ≥18%
Intensity of flame (parameter 954) >24%
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CC1P7546en
17.12.2018