pH Probe Calibration Issues: Is it Out of Service?

Client:
Hello, I had a small question. I calibrated my pH probe with neutral pH of 7 and 10. However, when I put my probe back, the value does not go below 14 even though I had performed the pH calibration before. Could it be possible that the probe is out of order?

Technical Advisor:
Yes, it is possible that your probe is out of order. I suggest you perform this test: https://ph-redox-pool.com/gb/content/16-ma-sonde-ph-est-elle-hors-service-

Client:
OK, thank you.