Well........the cost of an He analyzer is certainly a factor in that decision.
Depending on how and more importantly WHO is doing your trimix fills, an He analyzer isn't near as important.
Not that I have done piles of trimix, because that certainly isn't the case, and although I have had my mix checked with an He analyzer a couple times, it's not the worry that an Oxygen reading being "out" would be.
Some of the more learned folks here would probably tell you the same. Honestly, the He being out by even 5%, which is a gross blending error, wouldn't be catastrophic at all, which includes your decompression schedule, for a whole pile of gives that your "average" tech diver will ever do.
Bottom line.........I'd never purchase an He analyzer at current prices. I have and will continue to dive Trimix without analyzing the He content, but NEVER without analyzing the O2. You can also infer a fair amount of He "value" off of the O2 reading, there again, depending on "how" you mix, this can be more or less accurate, but more than accurate enough.
Caveat: If there's an He analyzer available, of course I'd double-check. It's in my nature.
Regards
Steve
