MiniProbe M7873

Zirconia Flue Gas Analyser


Self-heated probe, designed to measure Oxygen in flue gas (up to 700°C) for combustion efficiency and fuel saving in small and medium boilers fed by Natural Gas, light and medium oils, Oxygen control in drying biological muds process, measure of water vapor content in Textile and Pulp&Paper.

Available as a transmitter with 4-20 mA output from the probe head or combined with a control unit / display.

MiniProbe M7873 is the only SIL 2 compliant Zirconia in situ analyser able to ensure a reliable O2 measure in safety-demanding applications such as biological mud dryers

Measureable Gas

Oxygen [O2]

Water [H2O]


Main Features

Extreme Roughness

  • Rugged materials contacting the process gas
  • Usable in flue gas up to 700°C, either continuously or cyclically
  • Do not suffer damage or deformation
  • Installation and protection tube makes the probe suitable for high dust flue gas


Installation and Protection Tube

  • The MiniProbe can be equipped with a rugged AISI protection tube with an integral filter to ensure:
  • Effective protection from dust & abrasion
  • No direct sticking of dirty material on the sensor
  • Easier installation


Easy to Use

  • Direct insertion into the duct or pipe
  • Possibility to verify the calibration without removing the probe from process


European Compliance

  • Low Voltage Directive 2014/35/EU
  • EMC Directive 2014/30/EU



MiniProbe M7873 is optionally available SIL2 compliant in accordance to normative IEC/EN 61508 : 2010 (parts 1 to 7)


Accuracy0.1% O2 below 5% or 2% of reading above 5%
Repeatability± 1% of reading (short term)
Output Resolution0.01% O2
Response TimeSensor: 0.1 sec. ; Overall system < 5 sec.
Flue Gas Temperatureup to 700°C (on request up to 800°C)
Insertion Length100 / 200 / 300 mm
Process Connection3/4” NPT-F or 2” NPT-F with installation and protection tube
Ambient Temp. InfluenceProbe: max ± 0.005% of reading per °C.
External head: max. 0.06% of reading per °CExternal head: max. 0.06% of reading per °C
Atm. Pressure Influence1% of reading per 1% change in ambient pressure.
Probe Head ProtectionIP65
Head Temperature-5°C…+55°C
WeightProbe: 1 Kg. ; Installation tube: 1 Kg.
Wiring ConnectionsN°2 cable glands for cables max. 13 mm and inner terminal strip
Pneumatic ConnectionsCalibration inlet: 1/8” NPT-F
Measuring PrincipleZirconium Oxide (Zirconia). Micro-pod sensor technology with no need of reference air
Humidity0….90% non-condensing
Analog Output1 x 4-20 mA linear output proportional to range; max. load 500 Ω (or 350 Ω with galvanically insulated module) or logarithmic 50 mV/decade *
Ranges0-5 / 0-10 / 0-25% O2 (to select at order)
Diagnostic NV Logical Output (non-valid)Logical Non Valid output from relay free contact. Normally supplied in fail safe condition (triggered relay and closed contact if not in alarm). Can be modified in field **
Power Supply24 VAC ± 10%, 50/60 Hz, 50 VA
*Output from probe when connected to a remote ADEV control unit
**Mandatory for probe SIL2 compliant
Control Unit
ADV222 specifications (common to all versions)
Analog Inputs2 x isolated.
Analog Outputs2 x isolated
Output Resolutionbetter than 1x10.000 of FS
RelaysN°2 relays SPDT, 230 VAC, nominal 2A (max 4A) ***
Power Supply8...28 VDC ; 9...24 VAC
Ranges0-25% O2 ****
Operative Temperature-20°C…+70°C
Humidity0….90% non condensing
LedPower supply (blue) - Cumulative inputs overload (red) - TX/RX (yellow/amber)
Serial InterfaceRS485 2-wire (Protocol ModBus-RTU)
Line Impedance120 ohm
Termination TypeExternal
Max Speed57600bps
Max No. of Nodes32
Weight900 gr.
ConnectionsRemovable screw terminals pace 5,08 mm
Conductor SectionMax. 2,5 mmq
MountingDIN rail
***Threshold to be selected at order (factory set) or settable in field by PC with ADEV Easy Configurator or by display if ADbox or ADcaseM are selected
****Default range factory set. Modifiable on request at order on customer specification or by PC with ADEV Easy Configurator
Supplementary ADbox Specification
Weight8 Kg.
Dimensions400 x 300 x 150 mm
DisplayLCD 2.42” OLED. Resolution0.01%
Cable Entrance (bottom)N°4 cable glands PG 13 / 9 / 7
Supplementary ADcase Specification
Weight10 Kg.
Dimensions400 x 300 x 150 mm
DisplayLCD 2.42” OLED. Resolution0.01%
Cable Entrance (bottom)N°4 cable glands PG 13 / 9 / 7
Pneumatic ConnectionsCalibration air inlets: 1/8” NPT-F
ConfigurationsADcaseM-1: Pressure reducer and manual valve
ADcaseM-2: Pressure reducer and electro valve


Boilers using any type of fuel: Natural gas, LPG, light oils, heavy oils, diesel and biomass

Biomass Plants


Low Temperature Incinerators

Biological Muds Dryers (safety)

H2O measurement in drying processes: Textile, Pulp&Paper, Tissue, Wood, Concrete

Other combustion processes where flue gas is within temperatures limits (within 700°C)


Sampling System

MiniProbe M7873 is also available with bypass cell in SS316 for extractive applications.


Measuring Principle


The measuring principle on which the analysis is based is linked to the use of Zirconium oxide which, at high temperatures, can behave like a solid state electrolyte, developing an electromotive force on two electrodes placed in contact with different O2 concentrations (partial pressures), proportional to the temperature in Kelvin degrees (°K) and the logarithm of the ratio between the two pressures PO2’ and PO2” in accordance with Nernst’s well-know ratio:


E = RT / nF (Lg P02’ / P02“)


Where:           R = Perfect gas constant (8,31 Joule/degree bulk)

                       F = Faraday’s constant

                       T = Absolute temperature in °Kelvin

                       n = 4



The inner sensing element is a based on a proprietary ADEV technology (micro-pod) and features a solid state reference that completely eliminate the need of a reference air flow, making the instrument very easy and practical to use in field.

  • No reference air
  • Sensor on the tip
  • No gas circulation