What statistic to use?

#1
I am reviewing the statistics we currently use at work to ensure that we are using the correct statistics. The scenario is:
a. We produce instruments that process batches of 10 samples, and each of those samples is given a pass or fail after processing.
b. When we make changes to the instrument we need to ensure that the changes have not made any differences to (or have improved) the performance of the instrument.
c. We run many batches (as many as 20 (therefore 200 samples) on the updated instrument and also on the current instrument)and want to determine if the instruments are equivalent.

The questions are:
1. What is the best test to determine if the instruments are equivalent?
2. What formula do I use to determine the actual number of batches or samples needed to test this equivalence?

If anyone can help with this it would be much appreciated.
 
#2
Find the critical parameter you instrument should do & find new measurement after changes are made to instrument.
Use nonparametric test to find differences if any.