Calibration Query

[JonG]

I think I am right in saying that calibration should be completed infrequently, so that any gradual cell deterioration or developing issue isn't masked.

If so when do you calibrate and if you change 1 cell every 6 months to avoid batch manufacturing issues and then calibrate, doesn't this compromise the concept above?

[graham_hk]

I replace my 3 cells all at the same time within 12mo of manufacture and calibrate everyday. Have done for nearly 20years. I keep a note of Millivolts and make sure they reach expected on calibration as opposed to just calibrating blind - it’s less hassle (for me) to calibrate than flush with o2 and checking 1.0 is reached

[matt]

You are always best following manufacturers advice IMHO.

I calibrate each day, but I also keep a note of the end-cal value which clearly shows changes over time. I also check the last calibration is still good in air as well as in O2.

Matt.

[ebt]

On a KISS I calibrate...then for subsequent dives will usually do a cal check (ie does it reach what I expect). I'd try to avoid re-calibrating when the cell faces are moist, so generally that means a recal every few days on a multi day trip.

[notdeadyet]

I re-cal if/when the cells aren't reading right. I'd tolerate down to about 0.97 without, any less and I will re-do it. I know the received wisdom is that calibration is just calibrating over errors but that also assumes you have the memory of a goldfish.

I used to cycle a new cell in every six months but got out the habit. Last few years I've just taken the winter off rather than do unsatisfying diving just for the sake of getting in the water so the 6 month cycle seemed pointless. I replace the cells with a full set at the end of winter now and change them out a year later. I've found that I need to calibrate less often that way, too. I guess because they are aging at the same rate and never nearing end of their life so they are staying in the same range. On the 6 month cycle you'd always have one really old cell that would drift off cal sooner than the others do. As for cost, two cells a year vs. three isn't really anything to get excited about in the grand scheme of things.

[matt]

I re-cal if/when the cells aren't reading right. I'd tolerate down to about 0.97 without, any less and I will re-do it. I know the received wisdom is that calibration is just calibrating over errors but that also assumes you have the memory of a goldfish.

I used to cycle a new cell in every six months but got out the habit. Last few years I've just taken the winter off rather than do unsatisfying diving just for the sake of getting in the water so the 6 month cycle seemed pointless. I replace the cells with a full set at the end of winter now and change them out a year later. I've found that I need to calibrate less often that way, too. I guess because they are aging at the same rate and never nearing end of their life so they are staying in the same range. On the 6 month cycle you'd always have one really old cell that would drift off cal sooner than the others do. As for cost, two cells a year vs. three isn't really anything to get excited about in the grand scheme of things.

I do 4 month swap, but agree it is a PITA. Especially when you forget or get them 2 months apart and get the same batch regardless!

[notdeadyet]

I do 4 month swap, but agree it is a PITA. Especially when you forget or get them 2 months apart and get the same batch regardless!

Mine are made to order so not really any issue with batching if you are cycling one at a time. Any saving in doing two a year instead of three is balanced out with the shipping costs from the US for a single cell (not cheap). I'm not sold on either way of doing it, they both have pluses and minuses. If I was diving year round I'd probably still cycle them. I find winter diving less satisfying than I used to do so I am happy taking a break, doing other things and mothballing the unit for 4-5 months. Not much sense paying for cells to sit in the cupboard. I might go crazy and have my first ever diving holiday abroad this winter so will see.

[Paulo]

Made to order? Can you not just change the connector on your cables and use mire commonly available cells?

[Capt Morgan]

Made to order? Can you not just change the connector on your cables and use mire commonly available cells?

I'm fairly sure they run a higher milivoltage than most cells.

[Paulo]

I'm fairly sure they run a higher milivoltage than most cells.

I guess it takes more power to run something that was made with the same technology as the Apollo spacecraft

[notdeadyet]

Made to order? Can you not just change the connector on your cables and use mire commonly available cells?

Why would I want to? Lifespan is longer and reliability is about a million times better than those shitty magic pebbles in the Inspo

I guess it takes more power to run something that was made with the same technology as the Apollo spacecraft

Fuck me, the amount of support you've had to ask for for that Lada made thing you've got you'd think it was a mail order Russian bride

[Paulo]

Why would I want to? Lifespan is longer and reliability is about a million times better than those shitty magic pebbles in the Inspo



Fuck me, the amount of support you've had to ask for for that Lada made thing you've got you'd think it was a mail order Russian bride

[JonG]

So what are the pros and cons of frequent versus infrequent calibration?

[dwhitlow]

You are always best following manufacturers advice IMHO.

I calibrate each day, but I also keep a note of the end-cal value which clearly shows changes over time. I also check the last calibration is still good in air as well as in O2.

Matt.

Perhaps I should follow the manufacturer's advice, but I don't. After all, they did send me APD12s and tell me they were good, whilst telling me other cells were unsuitable, until they later decided to call those same cells APD16s and supply them to their customers. I like to put my intellect and instincts ahead of brand loyalty and marketing.

When my cells are dry I look at the ppo2 readings on my plumbed in OSTC cR (which monitors cells 2, 3 and 4) and if they read close to .21 I assume nothing has changed and assemble my unit. After pressure tests I switch on and expect to see very similar readings on handset and OSTC cR. Assuming that is the case I go diving. As I ascend and approach 6m I flush my unit with oxygen until I see all the cells read 1.6. I then feel happy they aren't dying.

Occasionally I do calibrate but would never do so if my cells were not dry as water on the cell surface might affect calibration values.

I also change a cell every 4-5 months and avoiding fitting cells from the same batch at the same time and relegate the replaced cell to cell #4.

[JonG]

So what are the pros and cons of frequent versus infrequent calibration?

Bump:

I am thinking that frequent calibration, could mask another issue, unrelated to cell health, maybe wiring for instance so you end up calibrating over it and not spotting the problem when cells are checked?

In-frequent calibration could result in cell drift, but if the o2 checks on the surface, and then at 6m on dive are not conducted correctly (adequate flushing etc.) the drift could be missed.

Or am I way off?