58 Lambda oxygen sensors A B
“Lambda” oxygen sensors, Type LSM 11
For measuring the oxygen content
λ
U
Principle of the galvanic
oxygen concentration cell with
solid electrolyte permits mea-
surement of oxygen
concentration, for instance in
exhaust gases.
Sensors with output signal
which is both stable and
insensitive to interference, as
well
as being suitable for extreme
operating conditions.
Application Range Installation instructions
Combustion processes The Lambda sensor should be installed at
Sensor
– Oil burners a point which permits the measurement of
Total length = 2500 mm 0 258 104 002*
– Gas burners a representative exhaust-gas mixture, and
Total length = 650 mm 0 258 104 004
– Coal-fired systems which does not exceed the maximum
* Standard version
– Wood-fired systems permissible temperature. The sensor is
– Bio refuse and waste screwed into a mating thread and tightened
– Industrial furnaces Accessories with 50…60 N · m.
Connector for heater element – Install at a point where the gas is as hot
Engine-management systems
Plug housing 1 284 485 110 as possible.
– Lean-burn engines
Receptacles 1) 1 284 477 121
– Gas engines – Observe the maximum permissible
Protective cap 1 250 703 001
– Block-type thermal power stations temperatures.
Connector for the sensor – As far as possible install the sensor
Industrial processes vertically, whereby the electrical
Coupler plug 1 224 485 018
– Packaging machinery and installations connections should point upwards.
Blade terminal 1) 1 234 477 014
– Process engineering
Protective cap 1 250 703 001 – The sensor is not to be fitted near to the
– Drying plants
– Hardening furnaces exhaust outlet so that the influence of the
Special grease for the screw-in thread outside air can be ruled out. The exhaust-
– Metallurgy (steel melting)
Tin 120 g 5 964 080 112 gas passage opposite the sensor must be
– Chemical industry (glass melting) 1) 5 per pack
free of leaks in order to avoid the effects of
2 needed in each case leak-air.
Measuring and analysis processes
– Smoke measurement – Protect the sensor against condensation
– Gas analysis Special accessories water.
– Determining the Wobb index – The sensor body must be ventilated from
Please enquire regarding analysing unit
LA2. This unit processes the output signals the outside in order to avoid overheating.
from the Lambda oxygen sensors listed – The sensor is not to be painted, nor is
here, and displays the Lambda values in wax to be applied or any other forms of
digital form. At the same time, these values treatment. Only the recommended grease
are also made available at an analog is to be used for lubricating the threads.
output, and via a multislave V24 interface. – The sensor receives the reference air
through the connection cable. This means
that the connector must be clean and dry.
Contact spray, and anti-corrosion agents
etc. are forbidden.
– The connection cable must not be
soldered. It must only be crimped,
clamped, or secured by screws.
B A Lambda oxygen sensors 59
Technical data
Application conditions
Temperature range, passive (storage-temperature range) –40…+100 °C
Sustained exhaust-gas temperature with heating switched on +150…+600 °C
Permissible max. exhaust-gas temperature with heating switched on
(200 h cumulative) +800 °C
Operating temperature
of the sensor-housing hexagon ≤ +500 °C
At the cable gland ≤ +200 °C
At the connection cable ≤ +150 °C
At the connector ≤ +120 °C
Temperature gradient at the sensor-ceramic front end ≤ +100 K/s
Temperature gradient at the sensor-housing hexagon ≤ +150 K/s
Permissible oscillations at the hexagon
Stochastic oscillations – acceleration, max. ≤ 800 m · s–2
Sinusoidal oscillations – amplitude ≤ 0.3 mm
Sinusoidal oscillations – acceleration ≤ 300 m · s–2
Load current, max. ±1 µA
Heater element
Nominal supply voltage (preferably AC) 12 Veff
Operating voltage 12…13 V
Nominal heating power for ϑGas = 350 °C and exhaust-gas flow speed
of ≈ 0.7 m · s–1 at 12 V heater voltage in steady state ≈ 16 W
Heater current at 12 V steady state ≈ 1.25 A
Insulation resistance between heater and sensor connection > 30 MΩ
Data for heater applications
Lambda control range λ 1.00…2.00
Sensor output voltage for λ = 1.025…2.00 at ϑGas = 220 °C
and a flow rate of 0.4…0.9 m · s–1 68…3.5 mV 2)
Sensor internal resistance Ri~ in air at 20 °C and at 12 V heater voltage ≤ 250 Ω
Sensor voltage in air at 20 °C in as-new state and at 13 V heater voltage –9...–15 mV 3)
Manufacturing tolerance ∆ λ in as-new state (standard deviation 1 s)
at ϑGas = 220 °C and a flow rate of approx. 0.7 m · s–1
at λ = 1.30 ≤ ±0.013
at λ = 1.80 ≤ ±0.050
Relative sensitivity ∆ US/∆ λ at λ = 1.30 0.65 mV/0.01
Influence of the exhaust-gas temperature on sensor signal for a temperature increase
from 130 °C to 230 °C, at a flow rate ≤ 0.7 m · s–1
at λ = 1.30; ∆ λ ≤ ±0.01
Influence of heater-voltage change ±10 % of 12 V at ϑGas = 220 °C
at λ = 1.30; ∆ λ ≤ ±0.009
at λ = 1.80; ∆ λ ≤ ±0.035
Response time at ϑGas = 220 °C and approx. 0.7 m · s–1 flow rate
As-new values for the 66% switching point; λ jump = 1.10 ↔ 1.30
for jump in the “lean” direction 2.0 s
for jump in the “rich” direction 1.5 s
Guideline value for sensor’s “readines for control” point to be reached
after switching on oil burner and sensor heater;
ϑGas ≈ 220 °C; flow rate approx. 1.8 m · s–1;
λ = 1.45; sensor in exhaust pipe dia. 170 mm 70 s
Sensor ageing ∆ λ in heating-oil exhaust gas after 1,000 h continuous burner operation
with EL heating oil; measured at ϑGas = 220 °C
at λ = 1.30 ≤ ±0.012
at λ = 1.80 ≤ ±0.052
Useful life for ϑGa < 300 °C In individual cases to be checked by
customer; guideline value > 10,000 h
2) See characteristic curves. 3) Upon request –8.5...–12 mV.
Warranty claims
In accordance with the general Terms of
Delivery A17, warranty claims can only be
accepted under the conditions that
permissible fuels were used. That is,
residue-free, gaseous hydrocarbons and
light heating oil in accordance with DIN
51 603.
60 Lambda oxygen sensors A B
λ
U
Dimension drawing.
A Signal voltage, B Heater voltage, C Cable sleeve and seals,
D Protective tube, E Protective sleeve, L Overall length. ws White,
sw Black, g Grey.
L
66 L-200
28,2
M18x1,5 6e
10,5 ws
21,8
SW 22
C B
ø 22,6
ø12
X
sw +
+ -
g -A
E
D X
73
Lambda sensor in exhaust pipe (principle). Characteristic curve: Propane gas Characteristic curve: Complete range.
1 Sensor ceramic, 2 Electrodes, 3 Contact, (lean range). 1 Closed-loop control λ = 1; 2 Lean control
4 Housing contact, 5 Exhaust pipe, 6 Ceramic a Rich A/F mixture, b Lean A/F mixture
;;;;;
protective coating (porous).
mV
UH = 12 V mV UH = 12 V
30
ϑA = 220°C 800 ϑA = 220°C
a
Exhaust gas Air
Sensor voltage US
1
;
Sensor voltage US
4
5 6 20 600
Us
400
;;
3 10
200
2
0 b
1 2
2.0 λ
;
1.0 1.2 1.4 1.6 1.8 0.8 1.0 1.2 1.4 1.6 1.8 2.0
3.31 5.71 7.54 8.98 10.14%O2 Excess-air factor λ
Design and function The active sensor ceramic (ZrO2) is heated The special design permits:
The ceramic part of the Lambda sensor from inside by means of a ceramic Wolfram – Reliable control even with low exhaust-
(solid electrolyte) is in the form of a tube heater so that the temperature of the gas temperatues (e.g. with engine at idle),
closed at one end. The inside and outside sensor ceramic remains above the 350 °C – Flexible installation unaffected by external
surfaces of the sensor ceramic have a function limit irrespective of the exhaust- heating,
microporous platinum layer (electrode) gas temperature. The ceramic heater – Function parameters practically
which, on the one hand, has a decisive features a PTC characteristic, which independent of exhaust-gas temperature,
influence on the sensor characteristic, and results in rapid warm-up and restricts the – Low exhaust-gas values due to the
on the other, is used for contacting power requirements when the exhaust gas sensor’s rapid dynamic response,
purposes. The platinum layer on that part of is hot. The heater-element connections are – Little danger of contamination and thus
the sensor ceramic which is in contact with completely decoupled from the sensor long service life,
the exhaust gas is covered with a firmly signal voltage (R ≥ 30 MΩ). Additional – Waterproof sensor housing.
bond-ed, highly porous protective ceramic design measures serve to stabilize the lean
layer which prevents the residues in the characteristic-curve profile of the Type Explanation of symbols
exhaust gas from eroding the catalytic LSM11 Lambda sensor at λ > 1.0...1.5 (for US Sensor voltage
platinum layer. The sensor thus features special applications up to λ = 2.0): UH Heater voltage
good long-term stability. – Use of powerful heater (16 W) ϑA Exhaust-gas temperature
The sensor protrudes into the flow of – Special design of the protective tube λ Excess-air factor 1)
exhaust gas and is designed such that the – Modified electrode/protective-layer O2 Oxygen concentration in %
exhaust gas flows around one electrode, system.
whilst the other electrode is in contact with
the outside air (atmosphere).
Measurements are taken of the residual
oxygen content in the exhaust gas.
The catalytic effect of the electrode surface
at the sensor’s exhaust-gas end produces
a step-type sensor-voltage profile in the 1)The excess-air factor (λ) is the ratio be-
area around λ = 1. 1) tween the actual and the ideal air/fuel ratio.
