Troubleshooting of pH and Redox probe calibration issues: an exchange between customer and technical advisor.

Client:
Hello, I received the two probes (PH and Redox ACL). The Redox probe is working fine! But I'm having an issue with the PH probe calibration.

Technical Advisor:
Hello, what seems to be the problem?

Client:
For the PH probe, I calibrate it with the received PH7.5 liquid... if I set the target to 7.2, the device pumps the PH- liquid... However, when I measure the basin 3 times with my testing device, I get a value of 7.1. I've calibrated multiple times and always get the same result.

Technical Advisor:
The fact that the pump is doing that is normal. It sees 7.5 and wants to go to 7.2.
Before anything else, do this small test https://ph-redox-pool.com/gb/content/16-ma-sonde-ph-est-elle-hors-service-

Client:
How can I correct this 4-value difference?

Technical Advisor:
By doing this, we will be certain that the probe is working.
After that, measure the standard solution with your device.
Then take a glass of water and measure the pH value with the probe and your device.

Client:
Okay, I will do that and get back to you later, but I have to leave for now!

Technical Advisor:
Okay, no problem. See you soon!