Analysen-, Mess- und Systemtechnik GmbH
ZrO2-Probes for the Measurement of Oxygen
in Flue Gases
The wide range of applications of ZrO2-probes for the measurement of oxygen requires
the adaptation of this measuring system to varying process conditions like temperature,
aggressive flue gas and even hazardous areas. A short response time and durability of the
sensor are further major customer demands. But also ease of use, reliability and minimum
maintenance of the analysis system are important design features.
Twenty years of experience in system technology enable AMS Analysen-, Mess- und
Systemtechnik to provide ZrO2-probes with these features already built-in while still
keeping an attractive price.
High-temperature probe AMS 3211-700, electronic controller AMS 3220 (EEx-version)
Applications System features
The oxygen measuring units are used for the Specially AMS designed sensor for flue
determination of the oxygen concentration in flue gas applications, operator replaceable
gases of incinerators or in pure industrial gases TÜV-approval for large boilers in power
covering the temperature range from 20°C to plants, industrial furnaces and for waste
1750°C. incenerators and for crematoria
Since the Zirconia measuring cell is located in Gas wetted parts made of stainless steel,
the flue gas flow the measurement takes place other materials are available
directly (in-situ) allowing the sample extraction Range of probe lengths from 150 mm
and conditioning system to be omitted. to 3000 mm
Specific applications demand probes aligned to Gas temperatures up to 1750°C
the particular process environment: e.g. to EEx d II B + H2-probe for zone 1
hazardous areas classified as zone 1 or 2, to Electronic controller:
residue free combustion processes using Self diagnostics with fault signals
natural gas or to flue gas ducts with small Automatic calibration
diameters. Plausibility check of the correction data
The oxygen measuring system consists of the ZrO2-probe with temperature controlled measuring cell,
the electronic controller as well as of the pneumatic unit for the air supply. The measuring procedure is
based on the galvanic oxygen concentration cell with solid electrolyte.
To match the varying application areas seven different probe models can be supplied. The electronic
controller is the same for all probes. The latter is installed separately but can be built into the pneumatic
cabinet as well.
Standard probe AMS 3211-500
The in-situ probe AMS 3211-500 for flue gas tem- only 2x4 screws are to be removed for this pur-
peratures up to 600°C (temporarily up to 800°C) pose.
is manufactured in three standard lengths (500 The 6 mm Swagelok gas inlets for calibration gas
mm, 1000 mm, 1500 mm) using stainless steel; and reference gas (instrument air) are fixed on
other lengths (150 mm to 3000 mm) are avail- the mounting flange of the probe.
able. Probes made of special materials like
INCONEL or Hastelloy C are supplied on demand.
The ZrO2-sensor is located directly in the flue gas
duct mounted on the probe tip. The specially de-
signed sensor used in all AMS Zirkonia probes
has a life-time of at least two years due to the low
operating temperature of less than 600°C.
The replacement of the O2-sensor is easily done:
High-temperature probe AMS 3211-700, up to 1100°C
The semi-extractive probe AMS 3211-700 gives pump is not necessary anymore.
the user some operating advantages, additional Being flange mounted outside the flue gas duct
to the high-temperature feature: the thermal load of the sensor is remarkably re-
Neither aspirator pump air nor reference air duced, thus increasing its life time to the
lines are needed customer´s benefit.
The aspirator pump, usually flange inte-
grated, can be omitted
The sensor life is substantially increased
The introduction of a Venturi gas jet at the top of
the probe is the basic innovation: The probe gas
flow through the Venturi generates a reduced
pressure in the inner tube of the probe thus suck-
ing flue gas through the perforated bottom plate
of the outer probe tube. That´s why the aspirator
High-temperature probe AMS 3211-600, up to 1750°C
The semi-extractive probe AMS 3211-600 can be the sensor via an aspirator pump integrated into
utilized at temperatures up to 1750°C employing the flange and will be fed back into the process:
a sample tube made of ceramic. Vertical set-up This arrangement keeps the dew point fixed while
of the probe will be provided in this case. Given a avoiding blockage of the measuring system.
maximum flue gas temperature of 900°C the fit-
ting position may be freely chosen when special
materials have been used in making the probe.
The standard length of the probe is 1000 mm,
other lengths (150 mm to 1000 mm) can be sup-
plied on demand.
The Zirconia measuring cell is built into the mount-
ing flange of the probe. The measuring gas passes
EEx-approved probe, up to 500°C
The EEx-probe features a flameproof enclosure
for the sensor with flame barriers to separate
safely the sensor from the flue gas and the elec-
trical connections from the ambient area.
The probe is certified for hazardous areas zone 1
at surface temperatures up to 160°C (T3) and
ambient temperatures until 40°C. The installation
lengths may vary from 150 mm to 860 mm. The
probe is designed for flue gas temperatures up Pneumatic unit and
to 500°C (short time 600°C). automatic calibration
EEx-approved probe for high tempera- To operate the ZrO2-probes, a reference gas as
tures, up to 1100°C well as a test gas for calibration is required. The
This particular design combines the characteris- corresponding tubing includes pressure control-
tic features of both the EEx-approved probe and ler (or diaphragm pump), filter, switching valves
the semi-extractive high-temperature probe 3211- and flow meter, all parts being mounted in a spe-
600. cial sample cabinet. For the gas supply, 6 mm
Flue gas temperatures up to 1100°C as well as Schott terminals have been chosen. Power and
hazardous zone 1 applications proof the outstand- signal connections are fitted to a row of terminals
ing capability of this specific ZrO2-probe. located in the sample cabinet.
As reference gas ambient air or instrument air
Residue free combustion processes: can be used.
Probe AMS 3211-500L Furthermore the automatic calibration of all AMS
For applications in combustion processes pro- ZrO2-probes within preselectable time periods is
ducing no residues,e.g. natural gas heating, we feasible while using the electronic unit AMS 3220.
recommend the probe AMS 3211-500L, properly
fitted to this application.
Ambient air is used as reference gas. As flue gas AMS 3220 electronic controller
ducts operate under pressure conditions slightly AMS 3220
below ambient, this low pressure will continu-
ously suck air into the stach via a capillary tube. F
This air passes by the reference side ot the AMS 3220
Zirkonia sensor and thereby provides the refer-
ence air required. reference gas
The probe will be delivered with a mounting flange for ZrO2-probe
DN65 PN6 and lenghts up to 500 mm, the weight reference air reference air
is approximately 3 kg. The other technical data
correspond to the probe AMS 3211-500. calibration gas
Small diameter ducts:
AMS Screw-in probe MV2
The ZrO2-sensor is to be fixed directly to the ex- flowmeter
haust duct with the flange featuring a metric M40x2 gas
thread, and likewise as all other AMS probes too, inlet
MV1: calibration gas for ZrO2-probe
MV2: control valve for calibration gas
shielded against dust particles from exhaust gas (air or test gas)
by a filter head made from stainless steel. The
weight is approximately 0,45 kg.
The flue gas temperature may amount up to 450°C
Pneumatic unit and electronic controller
at most, the stack´s diameter should be about Alternatively to the separate assembly of elec-
100 mm to 250 mm. As for the gas supply ambi- tronic controller and pneumatic unit both systems
ent air will be used as reference gas. A connector may be delivered installed in a single sample cabi-
for calibration gas or air can be added on demand. net.
Electronic controller AMS3220
The electronic controller AMS 3220 is the supply- consuming monitoring to a reasonable extent.
control- and evaluation unit for all AMS ZrO2- All instrument parameters, e.g. the calibration and
probes; the unit can be delivered in several hous- alarm data, the assignment of the display lines,
ing models. and of the two analogue outputs can be comfort-
The measuring range for flue gas applications cov- ably set at the control unit.
ers 0,1 - 25 vol-% oxygen permitting the operator
to adjust to the process values.
Considering process applications measuring
ranges from 1 ppm to 100 vol-% O2 can be ap-
plied. The calibration limits will be laid down in
the E-PROM of the controller correspondingly.
Programming and controlling the entire measur-
ing system will be executed with only three push
buttons: one for the operation mode, two for the
cursor. A display featuring two LCD rows indi-
cates the measuring value and user fed data as Particularly important regarding the reliability of
well as the operation directions in plain text mes- the O2 measurement is of course the identifica-
sages. A key operated switch locks the usually tion and hence the error message while calibrat-
locked programming level, accessible via an spe- ing: The stability of the measuring signal during
cific service mode, if required. calibration and the plausibility of the calculated
The self diagnostics of the controller with the cor- correction data are subject to the continuous
responding fault signals reduce the usually time check from the electronic controller.
Extended application areas for the AMS ZrO2-probes using
the electronic controller AMS 3220
The electronioc controller AMS 3220 succeeds the model AMS 3211. While keeping the well
known features some innovative functions have been integrated into the controller AMS 3220:
TÜV-approval for large boilers in power plants, for industrial boilers and furnaces, for
waste incinerators and for crematoria.
In connection with the appropriate pneumatic units for automatic calibration, it offers
the AUTOCAL routine.
For the EEx-d-probe, also an EEx-d-housing for the electronic unit can be offered.
Depending upon the application, either an EEx-IIC- or an EEx-d-IIB-housing is avail-
The housing of the electronic unit is made from painted steel sheet; the enclosure
complies with IP65 and warrants an improved dissipation of the heat produced.
Signal from the sensor and heating power are galvanically isolated to keep away
Galvanic separation of two 0/4 ... 20 mA outputs is standard.
An improved A/D-converter provides better resolution and the continuous measure-
ment from 25 vol-% down to 1 ppm Oxygen.
ZrO2-probe 3211-500 3211-500L 3211-600 3211-700 EEx-approved EEx-approved Screw-in probe
probe probe for high
operation mode standard in-line in-line probe for semi-extractive semi-extractive 2 in-line probes: 2 semi-extractive low-cost probe
construction sensor probe tip residue free high-temperature high-temperature EEx-ATEX 2G- high-temperature screwed into the
charateristics mounted combustion probe with probe approved probes with exhaust duct
sensor probe tip aspirator pump jet streaming for zone 1and aspirator pump: for ducts with small
mounted probe gas causing EEx-ATEX 3G for EEx-ATEX 2G and dimensions
an pumping effect zone 2 -3G approved
gas temperature 500°C 500°C 1700°C 1100°C 400°C 1100°C 450°C
protection IP65 IP65 IP65 IP65 IP65 IP65 IP 44
EEx d II B+H2 T3 EEx d II B+H2 T3
length 150 to 3000 mm 500 mm up to 1000 mm up to 1000 mm 150 to 860 mm up to 1000 mm ---
connection DN 65 PN6 DN 65 PN6 DN 80 PN16 DN 65 PN 6 DN 80 PN 40 DN 80 PN 40 connection thread
flange DN 65 PN16 DN 65 PN16 DN 100 PN16 DN65 PN 16 or larger or larger M 40*2
or lager DN 80 PN16
time constant <2s <2s <5s <5s <5s <5s <2s
t90-time < 10 s < 10 s < 20 s < 20 s < 20 s < 20 s < 10 s
position any any depending from up to 900°C: any any any any
but to be adjusted but to be adjusted sample tube adjusted but to be adjusted but to be adjusted but to be adjusted
downwards downwards material downwards downwards downwards downwards
vertical suspended vertical suspended
weight 6,5 kg 3 kg 6,5 kg 7 kg 10 kg 15 kg 0,3 kg
(at length ...) (1000 mm) (500 mm) (1000 mm) (1000 mm) (500 mm) (1000 mm)
ZrO2-probes 3211-500 3211-500L 3211-600 3211-700 EEx-approved EEx-approved Screw-in probe
probe probe for high
reference gas instrument air ambient air ambient air ambient air instrument air Iinstrument air ambient air
~supply or duct under- self diffusion self diffusion or or self diffusion
ambient air pressure causes ambient air ambient air
pump continuous sucking pump pump
calibration gas air and test gas air and test gas air and test gas air and test gas air and test gas air and test gas air or test gas
according to according to according to according to according to according to according to
measuring range measuring range measuring range measuring range measuring range measuring range measuring range
sample flow beyond 20 m/s beyond 20 m/s no limitations higher as 5 m/s beyond 20 m/s no limitations beyond 20 m/s
a shield made of a shield made of a shield made of a shield made of
stainless steel is stainless steel is stainless steel is stainless steel is
supplied to protect supplied to protect supplied to protect supplied to protect
the sinter filter the sinter filter the sinter filter the sinter filter
dust content beyond 5 g/m3 beyond 5 g/m3 beyond 20 g/m3 up to 20 g/m3 beyond 5 g/m3 beyond 20 g/m3 beyond 5 g/m3
a shield made of a shield made of a protection shield wet dust not a shield made of a protection shield a shield made of
stainless steel is stainless steel is made of stainless allowed! stainless steel is made of stainless stainless steel is
supplied to protect supplied to protect steel is supplied to protect steel is supplied to protect
the sinter filter the sinter filter recommended the sinter filter recommended the sinter filter
probe heating 10 minutes 10 minutes 10 minutes 10 minutes 10 minutes 10 minutes 10 minutes
cabinet system assembly eletrical connections gas connections protection dimensions w eight
w ith/w ithout
cabinet w indow
pneumatic unit gas supply clamp terminals 6 mm Schott terminals 300x400x200 mm 6,5 kg
compact unit gas supply and clamp terminals 6 mm Schott terminals 500x500x300 mm 1 2 kg
electronic controller IP56/IP66 (WxHxD)
Electronic controller AMS 3220
Measuring range(s) standard: 0,1 to 25 vol-% O2 for flue gas applications
option: 1 ppm to 100 vol-% O2 for process applications
Resolution of display 0,1 vol-% for measuring values >10,0 vol-%
0,01 vol-% for measuring values from 1,00 to 9,99 vol-%
display in ppmv for measuring values <1 vol-%
Measuring accuracy + 0,1 vol-% O2 for standard measuring range
Repeatability of the + 0,5 % rel. for range 25 vol-% to 10 vol-% O2
measuring signal + 0,05 vol-% O2 for range 10 vol-% to 0,2 vol-% O2
Drift/month 1 % rel. for standard measuring range, flue gas applications
Display alphanumeric display with 2 x 20 digits
Monitoring sensor voltage, heating cartridge (resistance), limits
Signal outputs 2 signal outputs 0/4 - 20 mA, galvanically isolated, max. load
600 Ohm, freely programmable from 0,1 to 25 vol-% O2
option: voltage output 0 - 1 V / 2,5 V
Galvanic isolation signal outputs, heating power for the sensor
Alarms for measuring signals 2 potential free relay contacts
max. 60 V 1 A
freely programmable for the entire measuring range
for limits as well as for fast/hold
Status output 1 potential free relay contact, max. 1 A / 60 V; for e.g.
sensor voltage, heating cartridge
Digital interface standard: RS232
Certifications TÜV-approved in compliance with European Directive
2000/76/EC for waste incinerators
TUV-approval for large boilers in power plants, for industrial
boilers and furnaces, for waste incinerators and for
Electrical safety CE 1996 as well as according to electromagnetic compati-
bility standards and safety rules for electrical instruments
Housing/Protection wall mounting case made of painted steel sheet/IP 65
EEx-II C- or EEx-dII B-housing
Dimensions 200 x 245 x 170 mm (WxHxD)
Weight approx. 3,5 kg
Ambient temperature -20°C up to +60°C
Voltage supply 230/115/24 V AC 48-62 Hz
AMS GmbH 7.3/2005 Subject to technical modifications Text, drawings and layout: Analytic Journal 7