1. ph-redox-pool.com

In order to check if your RedOx sensor is working, you can:

1) Dip the probe in a glass of water

2) Read the value in mV

3) Add salt to the water

4) Read the mV value again

If the mV value drops more than 100 mV then your probe is most likely working.

Warning: If your probe is old. It may not take time!