PROCEDURE PR36 - TEMPERATURE COMPENSATION TYPE SELECTION PURPOSE/SCOPE 1 min.
This procedure describes how to configure the temperature compensation state. This setting is available in both the Basic and Advanced programming modes. Parts
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PROCEDURE Temperature has two effects on electrochemical sensors. The Nernstian effect causes the sensor output to increase with increasing temperature. A pH sensor exhibits an increase of approximately: 7.00 pH 0.03 pH-------------------from --------------------pH unit 10째C
Since ABB sensors use a Silver/Silver Chloride measurement and reference half cell, the pH value where the sensor output is not affected by temperature (isopotential point) is 7.00 pH. The second effect of temperature is on the actual chemistry of the solution. Since ion disassociation is a function of temperature, measured ion properties such as pH, ORP and pION are affected by changes in process temperature. This effect cannot be predicted due to differences between solution chemistries. The temperature compensation state sets the compensation method to reflect these temperature effects. The three states of temperature compensation are: Manual Nernstian, automatic Nernstian and automatic Nernstian with solution coefficient. Table PR36-1 describes the function and programming mode of each state. Table PR36-1. Temperature Compensation States State
Display
Programming Mode
Function
Manual Nernstian
MANUAL
Basic and Advanced Used when fixed temperature value can be used instead of measured value. Initial value is 25째C. Use temperature calibrate state to change fixed temperature value. Nernstian compensation applied using fixed temperature value.
Automatic Nernstian
AUTO
Basic and Advanced Used when measured temperature value is being provided by temperature sensor. Nernstian compensation applied using measured value.
WBPEEUI520002A1
PURPOSE/SCOPE PR36 - 1