SO-B0-001

Limiting Current Type Sensor Oxygen Sensors

 

When voltage is applied to a zirconia electrolyte cell, oxygen is pumped through the zirconia disc from the cathode side to the anode side because the carriers of the current flowing through the zirconia electrolyte are oxygen ions. By attaching a cap with a pinhole on the cathode side of the cell and by increasing the voltage over the cell the current shows saturation due to the rate limiting step in the transfer of oxygen to the cathode. This saturation current is called limiting current and is nearly proportional to the ambient oxygen concentration.

 

Below the advantages of the oxygen sensor:
  measuring range 10 ppm to 1000ppm oxygen
  High accuracy
  For many types a more or less linear characteristic
  Small temperature dependence of the sensor signal
  Low interference with other gases
  Long service life
  In many cases " Single point calibration" necessary only once

 

Applications:
 Medical
 Laboratory
 Food industry
 Household/Gastronomy
 Measuring technique
 Security technology/Monitoring
 (Electrical-) industry

 

Characteristic Data:
Measuring gas: Oxygen concentration
Measuring medium: Gaseous atmosphere
Measuring principle: Limiting current type sensor
Measuring ranges: 10 ppm – 1000 ppm O2
Response time (t90): 2 to 25 sec. (Depends on: sensor type, gas flow, measuring chamber)
Sensor voltage / heating voltage / power consumption / heater cold resistance
    Sensor voltage:  0,7 to 1,6 Volt
    Heating voltage:  3.6 – 4.4 Volts
    Power consumption:  1.3 to 1.8 Watts (depends on application and packaging)
    Cold resistance:  R( 25°C ) = 3.25Ω ± 0.20Ω

Warm up time: Min. 30 s
Maximum permissible operating temperature: 350 °C (*)
*Depending on the cable and filter assembly (see paragraph: specification, Cable assembly)

Permissible volumetric flow rate (Purging the sensor)
    For all sensor types, the maximum flow rate depends on the way of purging the sensor (sensor in direct gas flow, gas beam shape, etc.) and the size of the measuring chamber. Exception: SO-E1-xxx (TO8 + hose connection for direct gassing). Permissible flow
[ml/min]: 100 - 500 (optimal: 250)

Lifetime (MTTF): ~ 20.000 hours (*)
* Depending on measuring medium. Stated lifetime refers to a heated, operated sensor of type SO-xx-250 and SO-xx-960. A failure or reaching the lifetime typically means a slight deviation from the dispatch specifications.

Vibration resistance
    Sensors based on the TO8 socket as well as those built with a TO39 socket (SO-Bx-xxx, SO-Ex-xxx, SO-Ax-xxx) meet the European Norm EN60068-2-6 (Sinusoidal vibration tests).