When I want to calibrate my probe in ph7 solution and when I press cal

When I want to calibrate my probe in the ph7 solution and when I press cal, the device tells me 0 when it should tell me 7. Does the problem come from the probe or from the device?

Do the following tests:

1) Restart your controller

2) Connect the probe

3) Dip the probe in a glass of tap water

4 ) Read the value

-case 1: no value, value 0,,,,: It is very likely that the sensor is faulty

-case 2: you should read a value between 6.5 and 8 (depending on the region), continue testing

5) Add vinegar to the glass

6) The new value should be at least 2 pH lower than the initial value

case 1: The value does not move or very 0.2 pH ...

case 2: Now we know that the probe is working at this instant. Note: Be careful in the case of an old or "tired" probe. it may not work all the time