Easy Peasy Hygrometer Calibration

[Mark Stone]

OP here! Funny, I don’t remember posting this lol - - Everyone’s comments today are great, and an interesting read. I still use the same method I described in post #1, and the guitars are doing fine. I would comment that checking the accuracy of a hygrometer and adjusting it is frequently “overthought” methinks. However, guitar maintenance - just like guitar playing - is not an exact art, and there are several routes to success. ��

[JayBee1404]

Originally Posted by Mandobart

Just a reminder from your former USN instrumentation tech that a salt test is NOT a calibration! It's a simple one-point cal check.

Unless you're testing the hygrometer's reading at 5 cardinal test points AND adjusting the response to be within a specific tolerance at these points, you're NOT calibrating anything.

It's just a go/no-go check of what your hygrometer reads at a single relative humidity value. Without knowing the range, span, linearity, etc. you can't know with any certainty if it reads X% off the actual value at more than the one point you tested.

BTW people who perform calibration on instruments used to monitor and control a nuclear power plant don't sweat non-identical readings in a given instrument loop, so long as they are all within their tolerance. And they know about hysteresis - an instrument will read one way on the way up from say 100 F to 500 F, but the response will be different from 500 F back down to 100 F.

So don't get all wadded up over a 2% - 6% difference between two or more hygrometers reading different values even when they're sitting right next to each other.

Most laypeople expect instrumentation to behave exactly linearly, repeatedly, identically and digitally (even when measuring an analog parameter). There are micro spatial and temporal relationships at work. It takes a few years of training and experience to learn this stuff. A little knowledge, mfr hype and OCD misunderstanding can cause you stress you really don't need.

This forum desperately needs a ‘Like’ button! Like, like, like!

If I was asked to summarise MB’s piece, I would say, “Don’t over-think this RH thing”.

[Jamolay]

Guilty of overthinking, about this and other things. But, not like harm is being done.

Mostly, I just find it funny that my two (same type/brand) humidistats seem to be all over the place out and about in my guitar room, then are practically identical inside the calibration bag.

Which, as mentioned, was a 32% bag to be at least a bit closer to my 40% ish goals than a 75% bag.

Part of the reason I did the “calibration” that is not really a calibration was because I was really curious about the local variations in the room.

It verifies that the humidity in my room is probably different in different locations. The humidity measured 2” off the floor is 50% and 2’ off the floor is 40%. The humidity measured by my humidifier is very different as well, so I want to adjust it using a humidistat that is as close to the guitar as possible. Maybe over the sound hole.

I also wonder if a small fan to better mix the air would even things out, even though it probably is not important.

Overall, I think my humidity is the best I can do right now, and adequate if not ideal. So I am scrutinizing it more than necessary, but that is who I am and I kind of enjoy these mini deep dives.

The next step is small Bluetooth humidistats I can hang inside the guitars! [emoji849]