PAROX 1000_e

OPERATING INSTRUCTIONS PAROX 1000

Paramagnetic Oxygen Sensor

Version 1.1

Bolstrasse 7, P.O. Box 574, CH-8623 Wetzikon 3

AUTOMATIC MEASURING SYSTEMS Tel. 0041/44/ 931 22 88 ?? Fax 0041/44/ 931 22 80 E-Mail: contact@mbe.ch ?? Internet: http://www.mbe.ch MBE AG

OPERATING INSTRUCTIONS PAROX 1000

1 DESCRIPTION.................................................................................................3

1.1 General Information and Options............................................................................................3

1.2 Measuring Principle..................................................................................................................4

1.3 Cross interference....................................................................................................................4 1.3.1 Zero calibration...............................................................................................................................5 1.3.2 Sensitivity calibration.......................................................................................................................5 1.3.3 Offset and slope settings for pressurised measurement ranges; e.g. 95 – 100 % O2............................5

1.4 List of Cross-Sensitivities.........................................................................................................6

2 TECHNICAL DATA............................................................................................8

2.1

2.2 General technical data..............................................................................................................8 PAROX 1000 Models.................................................................................................................9

2.3 Dimensions.............................................................................................................................10

2.4 Principal wiring diagram........................................................................................................11

2.5 Pin allocation D-Sub plug ST1................................................................................................12 2.5.1 Power consumption.......................................................................................................................12 2.5.2 Measurement signal output:...........................................................................................................12

2.6 Gas flow plan..........................................................................................................................13 2.6.1 Gas flow regulation with bypass regulator.......................................................................................13 2.6.2 Gas flow setting with fixed bypass..................................................................................................13 2.6.3 Gas flow without regulation............................................................................................................14

3 START-UP......................................................................................................15

3.1 Power switch-on.....................................................................................................................15

3.2 Measuring set-up....................................................................................................................15

4 TROUBLE-SHOOTING....................................................................................16

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OPERATING INSTRUCTIONS PAROX 1000

1

1.1 DESCRIPTION General Information and Options

The paramagnetic oxygen sensor is available as the following basic models:

¾ PAROX 1000 H, heated and thermostatically controlled model

¾ PAROX 1000 U, unheated model

The ambient temperature has a much lower effect on the H-type model than the U-.type model. For very accurate measurements and measurements of process and incineration waste gases, the H-type is recommended, to avoid the problem of understepping dew points of any components wherever possible.

The PAROX 1000 is in principle available for any desired range.

Smallest range 0 – 1 % O2

Largest range 0 – 100 % O2

Pressurised measuring range e.g. 95 – 100 % O2

or 18 – 22 % O2 are also available

The measuring ranges 0 – 25 % and 0 – 100 % O2 are available on stock. The available model versions are listed in section 2.2.

The various gas feed possibilities are listed in section 2.6.

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OPERATING INSTRUCTIONS PAROX 1000

1.2 Measuring Principle

Oxygen has a very high magnetic susceptibility compared to other gases, and thus displays a particularly paramagnetic behaviour. A small glass dumbbell filled with nitrogen and rotating on a taut platinum wire is suspended in an inhomogeneous magnetic field. This glass dumbbell is diamagnetic and tends to rotate out of the magnetic field. The strength of the resulting torque is determined by the susceptibility of the sample gas. This torque is compensated by a counter-torque induced by an electrically charged platinum coil on the dumbbell. The zero position of the dumbbell is controlled by means of an optical system consisting of a light source, a mirror on the dumbbell axis, and a pair of detectors. The difference between the compensating currents required to bring the dumbbell to the zero position in the presence of zero gas (i.e. no O2 present), or the sample gas, is proportional to the partial pressure of oxygen in the sample gas.

The PAROX 1000 measuring cell has a small measuring volume of approx.

3 cm3; the H-type is fully temperature-controlled.

Cross interference

The selectivity of the measuring system is based on the extraordinarily high susceptibility of oxygen. The susceptibilities of other gases are relatively so low that the presence of foreign gases can be ignored in most cases.

Significant measuring errors occur where the PAROX 1000 has been calibrated with nitrogen as reference gas, but the sample gas consists mainly of other gases with

considerable magnetic susceptibility. The PAROX 1000 then shows a measured value even if the sample gas contains no oxygen; i.e. it displays a cross-sensitivity to another gas.

The table in section 1.4 shows the measured values displayed when a gas is 100% present, and the PAROX 1000 is calibrated with nitrogen (zero) and oxygen (sensitivity).

Such gases often occur as process gases but are not available as test gases for calibration, especially not as a mixture. With the help of the table, the PAROX 1000 can be calibrated with nitrogen nonetheless.

First a simple example:

The oxygen concentration has to be measured in N2O (laughing gas), and this is not available as a test gas. The procedure is as follows: 1.3

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OPERATING INSTRUCTIONS PAROX 1000

1.3.1 Zero calibration

¾ read the cross-sensitivity from the list N2O ≠ - 0.2% O2

¾ supply N2 to the PAROX 1000

¾ adjust the zero potentiometer to an output value of +0.2% O2

¾ now the zero point for 100% N2O ≠ 0% O2

1.3.2 Sensitivity calibration

(test gas 20% O2, 80% N2)

¾ read the cross-sensitivity from the list N2O ≠ - 0.2% O2

calculate the cross-sensitivity value for the test gas:

- 0.2 x 80% = - 0.16

¾ calculate the sensitivity value for your test gas

(O2 test gas) -(cross-sensitivity value)

(20%) -(-0.16)

¾ supply test gas to the PAROX 1000

¾ adjust the span potentiometer to an output value of 20.16% O2

=sensitivity value =20.16% O2

Note: The mA and V values should be calculated in correspondence to

the measuring range and output range of the PAROX 1000.

(See Testsheet supplied with the PAROX 1000)

1.3.3 Offset and slope settings for pressurised measurement ranges; e.g. 95 – 100 % O2

¾

¾

¾

¾

¾

¾ Connect measuring instrument to the PAROX 1000 Flush PAROX 1000 with 95 % O2 (test gas or mixture with gas diluter) Set reading to 0 V/ 0 or 4 mA with zero point potentiometer Flush PAROX 1000 with 100 % O2 Set reading to 1V / 20 mA with sensitivity potentiometer Repeat comparison procedure with 95 % O2 and 100 % O2 until the required accuracy

is achieved

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