Emerson TCL instruction manual Calibration, Introduction, Calibrating Temperature

MODEL TCL	SECTION 9
	CALIBRATION

SECTION 9. CALIBRATION

9.1 INTRODUCTION

The calibrate menu allows the user to do the following:

1.Calibrate the temperature sensing element in the total chlorine sensor.

2.Calibrate the chlorine sensor.

3.Calibrate the analog outputs.

9.2 CALIBRATING TEMPERATURE

9.2.1 Purpose

The total chlorine sensor is a membrane-covered amperometric sensor. As the sensor operates, iodine, produced by the reaction between total chlorine and the vinegar/potassium iodide reagent, diffuses through the membrane and is consumed at an electrode immediately behind the membrane. The reaction produces a current that depends on the rate at which iodine diffuses through the membrane. The diffusion rate, in turn, depends on the concentra- tion of the iodine and how easily it passes through the membrane (the membrane permeability). Because membrane permeability is a function of temperature, the sensor current will change if either the concentration or temperature changes. To account for changes in sensor current caused by temperature alone, the analyzer automatically applies a membrane permeability correction. The membrane permeability changes about 3%/°C at 25°C, so a 1°C error in temperature produces about a 3% error in the reading.

Without calibration the accuracy of the temperature measurement is about ±0.4°C. Calibrate the sensor/analyzer

unit if...

1.±0.4°C accuracy is not acceptable

2.the temperature measurement is suspected of being in error. Calibrate temperature by making the analyzer reading match the temperature measured with a standard thermometer.

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