Flame Supervision; Ionization Probe - Siemens LME7 Series Basic Documentation

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Building Technologies Division
Infrastructure & Cities Sector

4.10 Flame supervision

4.10.1 Ionization probe

No-load voltage at terminal ionization
probe (X10–05, terminal 2)
Warning!
 The ionization probe must be protected against electric shock
hazard!
 When monitoring ionization currents in earth-free mains, connect
terminal X10-05/1 to burner ground
Short-circuit current
Required detector current
Possible detector current
Permissible length of detector cable (laid
separately)
Note:
As the detector line capacitance (line length) increases, the voltage at the ionization
probe und thus the detector current will drop. Extremely long line lengths and very
high-ohmic flames might necessitate the use of low-capacitance cable (e.g. ignition
cable). In spite of special electronic circuits designed to compensate possible adverse
effects of the ignition spark on the ionization current, it must be made certain that the
minimum detector current required is already available during the ignition phase. If
this is not the case, the primary ignition transformer connections must be
interchanged and/or the electrodes relocated.
Threshold values when flame is supervised by ionization
- Start prevention (extraneous light)
- Operation
100
90
80
70
60
50
40
30
20
10
0
Figure 3: Ionization input at AC 120 V/AC 230 V
Basic Documentation LME7...
4 Technical data
AC 300 V
Max. AC 1 mA
Min. DC 1 µA, display approx. 20%
Max. DC 40 µA, display approx. 100%
30 m (core-earth 100 pF/m)
- Start prevention (extraneous light)
- Operation
ION input
Ionization current in µA
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CC1P7105en
29.11.2011