Michell Instruments XZR200, User Manual

XZR200 User’s Manual

Michell Instruments

15

GOOD MEASUREMENT PRACTICE

5.2.2  Protecting from Water Droplets 

In environments where falling water droplets are likely, the sensor should be protected 

from water falling directly onto the very hot sensor cap as this can cause massive 

temperature shocks to the cell and heater. Popular methods include a hood over the 

sensor cap or for the sensor to be mounted in a larger diameter cylinder. 

At a very minimum the sensor cap should be angled downwards in the application as 

this will de

fl

 ect any falling moisture and prevent the sensor cap from 

fi

 lling with water 

(see Section 3, Installation).

5.2.3  Cross Sensitivity With Other Gases 

Gases or chemicals that will have an in

fl

 uence on the life of the sensor or on the 

measuring results are: 

1. Combustible 

Gases 

Small amounts of combustible gases will be burned at the hot Platinum 

electrode surfaces or Al2O3 

fi

 lters of the sensor. In general, combustion 

will be stoichiometric as long as enough oxygen is available. The sensor 

will measure the residual oxygen pressure which leads to a measurement 

error (low oxygen reading). The sensor is not recommended for use in 

applications where there are large amounts of combustible gases present 

and an accurate O

2

 measurement is required.

Gases tested: 

• 

H2 (Hydrogen) up to 2%; stoichiometric combustion 

• 

CO (Carbon Monoxide) up to 2%; stoichiometric combustion 

• 

CH4 (Methane) up to 2.5%; stoichiometric combustion 

• 

NH3 (Ammonia) up to 1500 ppm; stoichiometric combustion 

2. Heavy 

Metals 

Vapors of metals like Zn (Zinc), Cd (Cadmium), Pb (Lead) and Bi (Bismuth) 

will have an effect on the catalytic properties of the Pt– electrodes. Exposure 

to these metal vapors must be avoided. 

3. 

Halogen and Sulphur Compounds 

Small amounts (< 100ppm) of Halogens and/or Sulphur compounds have no 

effect on the performance of the oxygen sensor. Higher amounts of these 

gases will, in time, cause readout problems or, especially in condensing 

atmospheres, corrosion of sensor parts. These gases often outgas from 

plastic housings and tubes when hot. 

Investigated gases were: 

• Halogens, 

F

2

 (Flourine), Cl

2

 (Chlorine) 

• 

HCL (Hydrogen Chloride), HF (Hydrogen Fluoride) 

• SO

2

 (Sulphur Dioxide) 

• H

2

S (Hydrogen Sulphide) 

• Freons 
• CS

2

 (Carbon Disul

fi

 de)