pH electrode and voltage offset

[ScottHorn]

I use a pH electrode (with amplifier) as a detector for one of my instruments. I use a coefficient (approx 0.017 units/mv) so that 1 unit is approximately equal to 1 pH unit. The problem I have with this is that 0 mv across the electrode represents pH 7. Using this coefficient, without an offset, 0 mv reads as 0 pH. So far I have just mentally added 7 to all the values, as I'm not using this data quantitatively, only for controlling the process. Is there any way to add an offset in addition to a coefficient such that 0 mv is equal to 7 units. I'm aware that this is possible using a hardware solution, but I'd like to find a way to do it in software.

Scott Horn

[Daniel Mentlik]

Dear Scott,
this is something that is not easily done in Clarity. You can shift your data when they are already measured in the Chromatogram window by using the Chromatogram - Overlay - Move command, but this can neither be done automatically nor it can be done by a fixed amount.
Alternatively, you can also use offset on the signal axis in the Chromatogram window, which actually functions by fixed amount.

There may, however, exist one option for you, but only in case your A/D converter uses the 10 Hz sampling frequency, which means you have INT7. The way is little bit cumbersome, but allows you to display the data in correct form. How to do that:

• To the signal of INT7 in your configuration, also add the Virtual Detector (made by Knauer company) and add it to the Clarity Instrument
• Open the method and set the frequency of the INT7 card signal to 10 Hz
• Disable the INT7 card signal
• Switch to the Virtual Detector signal and change its frequency to 10 Hz
• Switch to the second tab of the Virtual detector signal and enter the External Source for Argument X, selecting the first signal of the INT7 card in the settings
• Modify the Resulting Formula field to x+7
• If you want the data to be absolutely same, change the Time Constant on the Detector Settings tab of the Virtual detector to 0.

The signal of the Virtual Detector will be 0.1s late compared to the INT7 signal, but otherwise, it is completely the same. Use any amendments in the INT7 integration table for the Virtual Detector signal from now on.

I have created a suggestion for this function for our A/D converters, but honestly do not believe the feature will be implemented any time soon.
Assigned an internal Suggestion ID: 38186