Flame Detector; Ionization Probe - Siemens LMV37.4 Series Basic Documentation

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4.4 Flame detector

4.4.1 Ionization probe

For continuous operation!
No-load voltage at ION terminal
(X10–05 pin 2)
Caution!
Protect the ionization probe against electric shock hazard!
Short-circuit current
Required detector current
Possible detector current
Max. perm. length of detector cable
(laid separately)
Warning!
Simultaneous operation of QRA... and ionization probe is not permitted!
Note
The higher the detector cable's capacitance (cable length), the more voltage at the
ionization probe, and thus the detector current, drops. Long cable lengths plus very
highly resistive flames might necessitate low-capacitance detector cables (e.g. ignition
cable). In spite of technical measures taken in the circuitry aimed at compensating
potential adverse effects of the ignition spark on the ionization current, it must be
made certain that the minimum detector current required is already reached during
the ignition phase. If this is not the case, the connections on the primary side of the
ignition transformer must be changed and/or the electrodes relocated.
Threshold values when flame is supervised by an ionization probe:
- Start prevention (extraneous light)
- Operation
100
90
80
70
60
50
40
30
20
10
0
0 2 4
Figure 4: Ionization input at AC 120 V / AC 230 V
Basic documentation LMV37.4...
4 Technical Data
Approx. U
Mains
Max. AC 1 mA
Min. DC 4 µA, flame display approx. 30%
Max. DC 16...40 µA, flame display
approx. 100%
3 m (wire–ground 100 pF/m)
Intensity of flame (parameter 954) ≥18%
Intensity of flame (parameter 954) >24%
ION input
6 8 10 12
Ionization current in A
14 16 18 20
27/235
CC1P7546en
20.09.2013