Question on "equivalence" in R71
 

Rule R71 states that I know we are supposed to go with the spirit of the rule and not be lawyers but I couldn't find a way to resolve this in my own head. What exactly is the definition of equivalence? Does equivalence mean the same part number, the part accomplishes the same task, equal performance, the same type of part, the same manufacturer but a different part number... What?

I would like to use something from the same manufacturer that accomplishes the same goal and is the same type of part but it is a different part number than the FIRST supplyers sell. It has slightly different specs that are at no advantage or disadvantage to us whatsoever. For our uses, the parts are identical. The only reasons for the different one is cost and time.

So what do you think?

Re: Question on "equivalence" in R71
 

I say good question for the Q&A...let them figure that one out

Re: Question on "equivalence" in R71
 

I would think that cost equivalence is one of the factors. The rules make a large fuss about accounting for the fair market value of things no matter if they were donated, bought on eBay, fell off the back of a truck, etc. So I think buying and "equivalent" part somewhere that's cheaper and costing the lower price might not come off well. So you might need to use the price of the piece you're saying it's equivalent to.

Re: Question on "equivalence" in R71
 

Unfortunately, there I don't think there is any way to provide a universally acceptable definition to the "equivalence" phrase for this context. It is much too application- and part-dependent.

For example, consider a resistor purchased from two different sources. The measured resistance of the two parts is identical. However, the body of one resistor (other than the color coding bands) is brown, while the other one is black. Are they "equivalent?" If you interpret equivalent to mean "identical" then they are not. If you interpret "equivalent" to mean "functionally equivalent for this application" then they are the same. For this application, the color is irrelevant.

But for another part in another application, color may be critical (e.g. a lens cover over a visible light sensor, which would affect the particular wavelengths detectable by the sensor, and therefore influence the sensor response).

One reasonable way to look at this is to try to determine the "functional equivalence" of two parts. The MINIMUM standard I would use would be "do they provide the same capability, and the same output response to equivalent input stimuli?" Because our robots are subject to such strict mass and volume guidelines, the parts may also have to pass a "do the parts weigh (approximately) the same and fill (approximately) the same volume?" test to be "equivalent" in the eyes of FIRST inspectors.

Realistically, if you are worried about this, you need to post a question to FIRST as soon as possible. They are the only ones that can give an official answer that you can use if questioned by an inspector.

-dave