Earlier this year I bought a SPG from Deep Six but never used it. I acquired a Perdix AI a few months ago, and last week my wife got her own Perdix AI.
I wanted to check her Perdix against mine before diving it and thought I’d use the Deep Six gauge as well.
On a full HP steel, both Perdixes showed identical pressure at about 3600, whereas the SPG showed about 3900.
I then put them all on a pony I have which I know to be about half empty. The Perdixes were again identical and read about 1350, whereas the Deep Six registered about 1425.
Were you comparing the 2 Perdix by having them both "read" the same transmitter? Or was each Perdix reading its own separate transmitter?
If they were both reading the same transmitter, then of course they will both show you the same number. They are both getting the same reading from the transmitter.
If they were each reading their own transmitter, then I would be very surprised if they gave you the exact same number. I would expect them to be very close, but not always exactly the same. I have 2 transmitters and when I put them both on my doubles, they always read very close but never EXACTLY the same.
All the comments in here about SPGs, combined with my own experience of never once having a problem with AI but exactly once having a spool O-ring on an SPG blow out, are why I only use AI these days and don't have an actual SPG on any of my reg sets (except for button gauges on my deco regs).