Which is more accurate when performing an ORP calibration: one point or two point?

Performing a two point calibration for an ORP sensor may make a user more confident in the measurement because it ties the measurement to two known millivolt values, offsets and slope values. When performing a pH calibration, the 2nd point is taken into consideration to account for aging of the pH measuring glass. Since an ORP measuring electrode is simply a piece of metal and not a glass bulb, performing a two point calibration does not provide any more accuracy than a single point calibration for ORP. Additionally, since ORP is not temperature compensated, the measurement must be done at 25 C to have any benefit. Therefore, it is generally acceptable to only perform a one point calibration for ORP.