Sensitometer exposure differences

 When addressing the question on whether one sensitometer should expose the same as another, there are a number of points to consider:

1. One sensitometer will always expose differently than another.  That is inherent in the technology and manufacturing methods used to build sensitometers.  Sending two sensitometers of the same model in for recertification at the same time with a request to have them factory calibrated to each other can improve inter-instrument agreement but there will still be differences.  Processor QC is not based on inter-instrument agreement, rather it is built on repeatability.  Sensitometers are not interchangeable on the fly and will require the establishment of new aims when one sensitometer is replaced by another sensitometer as supported by MQSA and FDA guidelines.  
2. As for two different models...X-Rite sensitometers are factory calibrated to their own model when they arrive for recertification. Because the 396 will be calibrated to the 396 master unit and the 393 is calibrated to a 393 master, there can be slight differences between the two factory calibrated units. Manufacturing differences between the two models can also result in differences in the exposure from model to model.  Once again, processor QC is based on densitometer and sensitometer repeatability, not inter-instrument agreement. 
3. If one sensitometer is exposing a great deal different than another, then the dip switches might be set differently on the two instruments.  Adjusting the dip switches on the bottom of X-Rite sensitometers can many times result in getting a second sensitometer to expose closer to the first.