It is important to calibrate a meter in order to ensure that the meter gives the correct readings.
Theoretically, the measurement of pH is a complex issue and with using the glass electrode a voltage is measured which is converted into a readable pH value on the display.
The calibration with pH 7 is intended to set the meter. Milli volts at 0 = pH7
Without calibration, the measurement can never work properly.
Beware: The electrode only works well if it is wet.
If the electrode has been stored for longer time, please use KCL storage solution before calibration.
This depends on the degree of use and on pollution on the spot, but at least every month.
Even if you get the meter for the first time and after each cleaning, calibration is necessary for a good measurement result.
Place the pH electrode in the pH 7 solution and wait for the reading to stabilize.
The electrode now gives a value of pH 7.01 again, if this is not the case, the instrument enables you to change to this value.
How You must set the instrument depends on the type of instrument, consult the manual for the meter.
Depending on the type, set the meter manually (turning a screw) or automatically (using a key combination).
pH 7 is exactly centered on the pH scale.
A pH meter must therefore always be calibrated first (calibrated) to pH7 to be in order to ensure that the measurements are carried out optimally.
After that you use the pH4.01 solution to adjust it to the right range.