Uv Flame Detectors Qra2 / Qra4 / Qra10 - Siemens LMV27.100x2 Basic Documentation

Measuring circuit for
detector current
measurement
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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 LMV27, it must be ensured that the basic unit is permanently
connected to power (EN 298), thus enabling the LMV27 to detect flame detector
failures during startup and shutdown.
Generally, the LMV27 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 the operation
mode
Possible detector current in the operation
mode
Permissible length of detector line normal
cable, lay separate
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 X10-06/2 against earth can destroy the QRA input

Simultaneous operation of QRA and ionization probe is not permitted!
Basic Documentation LMV27...
4 Technical Data
Max. 350 V peak
Min. 30 µA
Max. 600 µA
Max. 6 m
Intensity of flame (parameter 954) ≥18%
Intensity of flame (parameter 954) >24%
CC1P7541en
17.12.2018