Many electronically controlled rebreathers use an array of several sensors to alert the diver to the possibility of a failing sensor. The rebreather electronics will generate a warning indication when the sensors do not agree with each other. This is an important safety feature enabled by the multi-sensor array and the diver must respond immediately to sensor warnings.
If the sensor array contains a mix of brands or ages of sensors you may experience unexpected behavior of the sensor array that could result in misleading warnings. For example, installing a single new sensor in an array with much older sensors may cause sensor warnings simply because the new sensor responds faster than the older sensors. There are numerous other circumstances in which a mixture of brands or ages in an oxygen sensor array can cause otherwise acceptable sensors to generate a warning, solely due to ordinary differences between the sensors. You might see transient sensor warnings while the different sensors catch up to each other and auto calibrating rebreathers might even fail to calibrate in such situations.
Rebreather manufacturers each have specific recommendations regarding sensor replacement strategies for their rebreathers and we advise following their recommendations in order to avoid misleading warnings. If you are considering switching brands of sensors, it's tempting to want to just 'try one out' rather than replace the whole array, but we do not recommend mixing brands or ages of sensors.