SPLatco Knowledge Base

To calibrate the pH system, you must have fresh pH7 and pH4 buffer solutions. The temperature of these solutions must also be known at the time of calibration. If your pH probe has a PT1000 RTD sensor, then set the temperature compensation source to RTD and the temperature compensation will be done automatically. Similarly, if the program has been set up for a thermistor (correct polynomial values entered into the source code), then again the temperature compensation will be automatic.

If the pH probe does not have a temperature sensor, then the pH buffer solution temperature can be entered via the front panel buttons. For this, you will need to know the temperature of the buffer solutions by measuring it manually with a thermometer.

A table on the side of the buffer solution bottles shows what the actual pH is at the measured temperature and this must be entered via the front panel push buttons during calibration.

In calibration mode, the front panel push buttons have the following functions:

  • Input 12 – Increment the USER temperature setting (temperature of buffer solution)
  • Input 11 – Decrement the USER temperature setting (temperature of buffer solution)
  • Input 10 – Increment by 0.01 pH of buffer solution at the measured temperature (from table on buffer solution bottle or documentation)
  • Input 9 – Decrement by 0.01 pH of buffer solution at the measured temperature (from table on buffer solution bottle or documentation)
  • Input 8 – Calibration Step Button – Stages calibration procedure using LCD messages.
pH 7

After a long press of Input 8 (Menu / Calibration mode button), the unit will beep and display will display the following screens:

“pH Calibration “

” Mode “

“Use pH7 buffer “

“Set Temp and pH”

The pH probe must be place in pH buffer 7 solution. The LCD screen will look like this:

“Reading: 0.4986 “

“pH= 7.00 T= 77.0”

The reading is the raw value from the SX10507 and is displayed so that you can tell when the reading has settled (ie: value is no longer changing).

The temperature value T is displayed from the currently selected temperature source (as set previously in the Menu mode). If it is from the RTD or thermistor and the temperature sensor is in the buffer solution, nothing has to be done about it. If the temperature source is USER, then buttons Input 12 and Input 11 allow the user to set the temperature of the buffer solutions as they are used.

The pH value is the value that must be set for the measured pH 7 buffer solution temperature, using the buttons Input 10 and input 9. For example, if the temperature of the pH 7 buffer solution is 68°F (20°C), then from the pH table supplied with the buffer solution, the actual pH at this temperature of the solution is 7.02. In this case the user would press Input 10 button twice to get the displayed value to be 7.02.

Once the Reading is stable and the temperature and calibration pH values are correct, press Input 8 button – Calibration step button.

pH4

The display will now read:

“Reading: 0.5524 “

“pH= 4.00 T= 77.0”

Again, the temperature must be entered if the temperature source is USER.

The pH value must be adjusted using the tabulated data that came with the buffer solution.

Once this has been done and the Reading is stable, press Input 8 button, calibration step button.

Congratulations, you have now calibrated your pH system!