What is the effect of temperature on ORP?

Temperature compensation is a common requirement for accurate pH measurements, but not generally used for ORP. Why? pH is a measurement of the hydrogen ion concentration by the glass membrane. The voltage output of this glass membrane is temperature dependent, as is the hydrogen ion activity in the liquid. Temperature compensation will correct the pH voltage output back to a standardized 25°C. ORP differs from pH as it is not tied to a specific ion. The effects of temperature can be different depending on oxidizing and reducing substances present in the liquid. Due to this uncertainty, the ORP sensor output is uncompensated millivolts.