How Slow Digi Hygro?

[Herf N Turf]

A few months back, I broke down and "calibrated" my Madeline digi. I use quotes because, since it's got no provision for calibration, what I really did was "test" it. I hadn't bothered until then, since the analogue I was using was calibrated and the digi read dead on when compared to that.

So, off to the salt mines. I made the usual slurry of mortons and distilled water in a pepsi cap, inserted my salt and hygro into a zipper baggie and walked away... sort of. I kept looking at it every several hours and the readings were all over the map. It wasn't until (literally) hour 24 that the thing came to rest on 75%. Whew, what a relief to have what I already knew, confirmed.

Anyway, the question is, do these things really take 24hrs to render an accurate reading? It seems that whenever I open my box, the thing immediately rises or drops, depending on what's up in the outside world. But, in order to really know what's whats happening inside, while Im not looking, do I have to leave the box closed for a full 24hrs??

Thanks!

[SMOKE20]

Good question. I have always let it sit for at least 24 hours. sometimes a little longer.

[Herf N Turf]

Originally Posted by SMOKE20

Good question. I have always let it sit for at least 24 hours. sometimes a little longer.

Yeah, me too. That time I let it sit for 32hrs and it never moved once it hit 75%

[slyder]

I usually do mine for 24 to 36 hrs.

[dj1340]

It took 24hrs for the 2 I bought at Wally World. During that time the numbers were all over the place. Afterwards it set at 75% and never moved. Might have something to do with the salty air settling on the contacts. Thsi is only a WAG of course.

[karmaz00]

i lean towards 36 hours...

[Herf N Turf]

I think I've been misleading... sorry.

What I want to know is (once calibrated) how fast/slow are these things responding to changing levels? For example, if I open the box and set the hygo on the table, and it drops to 66%, is that to be considered accurate, or would it have to sit in that environment for 24hrs in order to be taken as gospel?

[dj1340]

When I open my humi, the reading drops. After I close it up mine usually go back to what it was a fairly quickly. Maybe an hour or less, depends on how long I had it open.

[LibertyToad]

I can't help but think that the salt test was originally done for analog hygros years ago and thus the 24-36 hour time period since the analogs react so much slower.

My digital resamples around every 5 minutes or so. I don't know this for fact, but I bet you could salt test using a digital and if you give it 10-12 hours it would be plenty.

[Jack Straw]

I think it depends on the hygro and the method it uses to measure. They all probably have different refresh rates, and different surface areas on whatever they use to measure which respond differently to changes in moisture.

That said, the reason you let a salt test sit for so long isn't that you need the hygro to stabilize, it's that you need to allow the salt/water enough time to stabilize - it has to absorb/release moisture into the air until it reaches a stasis at 75%.

[Herf N Turf]

Originally Posted by LibertyToad

I bet you could salt test using a digital and if you give it 10-12 hours it would be plenty.

Actually you can't. From what I've recently learned, it's not about how fast the hygro responds but how long it takes the salt slurry to take over the environment in the isolation medium. Unless you can get that medium down to the size of just the salt slurry and hygro, in most cases it's gonna take the full 24hrs to stabilize.

Thanks, Andrew. That's right on the money, bro.

[LibertyToad]

Originally Posted by Herf N Turf

Actually you can't. From what I've recently learned, it's not about how fast the hygro responds but how long it takes the salt slurry to take over the environment in the isolation medium. Unless you can get that medium down to the size of just the salt slurry and hygro, in most cases it's gonna take the full 24hrs to stabilize.

Thanks, Andrew. That's right on the money, bro.

Great info--thanks. I didn't consider that.