What is the difference between single junction or double junction pH & redox/ORP probes, what does GHL use?

What type of pH and redox/ORP probes does GHL use?

The quality of the measurement results is of essential importance. For this reason GHL uses only lab-grade double junction pH & redox/ORP probes, GHL does not and never did sell the cheaper and less reliable single junction probes.

What is the difference between a single & double junction probe?

The reference cell of a single junction probe only has a material similar to a wick (hereinafter referred to simply as “wick”) which is in direct contact with the solution to be measured. This is an essential part that enables the probe to function and also a part prone to disturbances.
The reference cell of a double junction probe has a wick that comes into contact with a second chamber filled with the same material as the reference cell. This second chamber also has a wick that is in direct contact with the solution to be measured. The second chamber slows down contamination, so double-connection probes can work reliably for up to 12 months or more if well maintained.
A double junction can also help protect the probe if the sample solution reacts and could form a solid sediment with the reference solution, clogging the wick and compromising its functionality.
Contamination can occur faster with a single junction probe than with a double junction probe, so a single junction probe has a shorter life.