Do RH gauges lose accuracy over time?

[Philc2001]

I've had multiple humidity gauges over the years and over time a few have stopped working so for Christmas I asked Santa for a couple of new adjustable gauges. I still have a pair of non-adjustable gauges I bought about 15 years ago, which have served me well and have been remarkably consistent between each other. When I first got them I did the salt test, and they were within 1%-2% below the esteemed 75% reference mark, so I always aimed for 1%-2% below my target for my humidors. 

With the new arrivals, as I've done in the past, I did the salt test. No surprise, the three new gauges came in 1%-2% below reference. This time, I tested again using my two old gauges along with the new ones to determine the range of drift between gauges. To my surprise I found the two old gauges to be 4%+ below reference. The temperature across all 5 gauges was within 1DF of each other, very nearly identical (< 1DF) to my reference La Crosse weather station, but the RH was all over the place. If this new reading is correct, my RH in my humidors has been around 65%-66%, well above my 61%-62% I was aiming for.

This begs the question; Do humidity gauges drift lower and lower over time? 

Do you all check your gauges regularly, and if so, what are your observations?  Based on this experience I will test my gauges annually from here onward. Should you also?

[havanaclub]

I have noticed my gauges to be not as accurate when batteries are low. One of my xikar has a low battery indicator which is nice. When this goes off I change all them. Which I need to do in the next few weeks.
Mine happen to read lower I find when battery is low.
But the difference between two different hydrometers with fresh batteries can be 1-3rh off I have noticed. Both salt tested at the same time. This must be the variance that they talk about on the product instructions.


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[Philc2001]

42 minutes ago, Hutch said:

When they start to err, I change the batteries. Works almost very time.

I changed batteries about 4 months ago, but I'll put in some fresh batteries and test again. Thanks. 

[Fugu]

Yes - and - yes.

And....changing batteries has no effect on sensor drift.

[OB1]

So.... sensors will drift in time. What’s the solution? Recalibrate or throw them out?

[El Presidente]

51 minutes ago, OB1 said:

So.... sensors will drift in time. What’s the solution? Recalibrate or throw them out?

i like using inexpensive Digital hygrometers. I change them every two years. My commercial grade hygrometers will  remain accurate 5-7 years. When they begin to drift I just mark on them +/- how many points they are out. 

[Philc2001]

4 hours ago, Hutch said:

Correct...depleted batteries does though. And changing to fresh ones can be the remedy.

I put fresh batteries in, but it had little effect; about +1% (batteries were only 4 months old), so the drift is still quite significant. Since these are not adjustable gauges I've relegated them to external duty.

Ironically, the RH in the house is normally around 45-50%, but lately it has been fairly steady in the mid 60s, which surprised me a bit. With the cool weather I was expecting the air to dry out, but the opposite appears to be happening. I guess with the cool temperature our AC is not kicking in and taking the humidity out of the air so the RH is equalizing and creeping up. You can really notice the effect in the early evening as soon as the sun sets, the temperature starts to fall from mid-high 70s down into high 50s or low 60s, and very quickly you can observe the damp air pushing the RH well into the 80s. I guess until it warms up a bit the RH will likely stay a little elevated, so I can't even dry out the humidor my simply leaving the door ajar. Fortunately 68% RH should not be detrimental to cigars, so I'm not worried about it, but it's interesting that most times we're trying to add humidity to our cigars, whereas now the natural RH in the house is higher than my target RH. Weird.

I'm going to set a reminder now to test my gauges at least once per year. 

[Philc2001]

56 minutes ago, Hutch said:

As temp drops RELATIVE humidity reading rises, without a change in the actual moisture in the air.  Mr Pig has explained this rather thoroughly in more than one post.

Yes, quite aware of the change in dew point relative to temperature. However, what seems to be happening here is more than the average RH swing. In fact, lately I've been seeing RH rise 30-35% (from high 50% to near 90%) in just 2 hours and ~8 degree shift in temperature. I never really noticed this before I put a gauge out there, now I watch it every time I go outside to smoke. We didn't have these kinds of swings in RH until about the past 6-8 weeks or so.