We are conducting weight tests on new media stock that is coming fully certified from out supplier.
(In fact it has been checked at the point of manufacture and by our supplier so our check is merely just us being cautious and checking everything)

Instead of testing the media by weight can we use the sieve analysis method to check size instead?

Media will be in only two possibilities, new or in-use.

If it's new you use the weight method.
If it's in-use you may use the sieve.

I want to point out the obvious, that new media inspection by weight is for cut wire media. We're assuming that's what you're working with since you mentioned inspection by weight.

This has me thinking.

AMS 2341/3D
Wire Quality
Paragraph 3.5 “Weight shall conform to Table 3 or 4 as determined in accordance with 4.1.3.2”.

Paragraph 3.5 is referring to the wire diameter prior to conditioning. Tables 3 and 4 states: "Wire Diameter" in inch and Millimeters. It does not state conditioned cut wire diameter. What happens to the wire when it is conditioned? Does it shrink or grow how much weight is lost during the conditioning process?

The answer to the original question can be found in section 4.1.3.1 which states: "Alternative methods for size evaluation may be used provided that they can be correlated to the weight method and are acceptable to the purchaser" So yes you can use a sieve test method as long as you meet the stated requirement.

Bottom line , In-process media testing uses the sieve test method. If the machine has a proper screening system, defective material should never come in contact with the part. This would only be an economic issue versus a quality issue. The over or undersize material would be discarded to the waste bins. If the amount in the waste bins is substantial then you know you have an issue with the as supplied product.