Calibration of SUSpH electrodes

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Hamilton SUS pH electrodes

Quality Declaration :

All sensors delivered with Quality Declaration The Quality Declaration contains all information needed for start-up

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Hamilton SUS pH electrodes

Quality Declaration : Zero point

Most equipment (controllers or transmitters) need zero point value and slope The zero point value is the mV value at pH 7, directly provided in the

declaration

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Hamilton SUS pH electrodes

Quality Declaration : Slope

The slope is calculated based on zero point value and pH 4 reading according to following formula (all mV values at 25°C) :

Slope= [E(pH4.01)-E(pH7.00)] /  [(pH=4.01) – (pH=7.00)]

In previous example : Slope = (181 – 4)/-2.99 = -59.2mV/pH

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Hamilton SUS pH electrodes

Quality Declaration : Zero point as pH value for 0 mV

Some equipment may need the slope and instead the zero point, they require the pH value to get 0mV. This one can be calculated as follows :

pH(E=0mV) =  [pH7*E(pH4) – pH4*E(pH7)]/(EpH4-EpH7)] =  

In previous example : pH(E=0mV) = [7.00*181 – 4.01*4] / [181-4] =

(1267– 16.04) / (177) = 7.067

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Hamilton SUS pH electrodes

During process calibration :

Some processes may require pH adjustments of the electrode during process and without removing the electrode from the vessel. This procedure is called “product calibration”. The user takes a sample of medium (through sterile sample valve) and makes a reference pH measurement (in lab). In case the reference value differs from process value more than a user pre-defined tolerance, an adjustment is required. It consists of an offset adjustment, the slope remains unchanged. Hamilton SUS electrodes can be handled is this way, the procedure however must be supported by the controller / transmitter.

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Thank you for your attention!

Hamilton Bonaduz AG, SwitzerlandHamilton Company, Reno / USA