KPH601 Online PH Sensor Signal Output: RS-485 (Modbus/RTU Protocol) 

1.Temperature compensation

This has to be taken into consideration if pH values obtained by different temperatures are to be compared. Furthermore, the slope depends on the temperature (Nernst equation): E = E0 – 2.303 RT / F  ∆ pH (R,F = constant) Where: E = measured potential E0 = zero point potential ∆pH = difference in pH between outside and inside of the glass membrane F = Faraday constant R = universal gas constant T = temperature Kelvin the slope increases with an increase in temperature (see “5.6 The influence of temperature on pH measurements“ on page 85). The most exact pH value is obtained when the temperature of the calibration and measured solutions are identical. pH Theory Guide 35 METTLER TOLEDO The temperature compensation of the transmitter corrects for this effect. An electrode would have an ideal temperature behavior if its calibration lines (isothermals) intersect at the zero point of the electrode (pH 7 = O mV) at different temperatures (see Figure 18 below). Figure 18 Calibration line and isothermal intersection points. Since the overall potential of the pH electrode is composed of the sum of many single potentials, which all have their respective temperature dependencies, the isothermal intersection hardly ever coincides with the zero point of the electrode (the ideal case would be: 0 mV at pH = 7/25°C). In the last few years, the development of the electrode has concentrated on bringing the isothermal intersection and the zero point as close ­together as possible, since the nearer they are to pH 7 the smaller the error in the temperature compensation. Besides, the measuring error increases with an increasing temperature difference be-tween the calibration and the actuai measuring. As a rule the errors are in the order of 0.1 pH units.
2.Technical Specifications

3.Dimensional Drawing

Note:The sensor connector is M16-5 core waterproof joint male head.

4.Installation

Note: The sensor should not be installed upside down or horizontally when installed, at least at an angle of 15 degrees or more.

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