sensor type

Your post is a little confusing, I will try to reply about what I understanded.

It seems that your company packs something you call blades in sets of 10, and need to control if each pack comes out with 10.

The solution depends on the size, the speed, the type of package you have, how much money you can spend in it and, related closely to it, what's the reliability you expect from your inspection process. It's not a "use this sensor" type of question.

Here go some suggestions. Please come up with more details about the blades and the package and let me see if I can help more:

- Put in your production line (transport conveyor, for example) one section with a dynamometer, feeling the weight of the packages. If they're lighter than they should, diverge to another line for review.

- Install an image recognition device that actually "take a look" at each package and count the number of blades.

- If the packages have standard dimensions depending on the blades inside, a simple deflector in the conveyor can direct the packages that are complete to the "ready" line, while the others go for inspection/rework.

Dynamometric is #1

Magnetic Coupling/differential transformer could be #2( depends on μ ,however)

On-the- go Levitation by Swept Pressure air wave(sensing pressure it lifted on)#3

Simple Electronics + any of #1,2,3 above will solve your problem.