Weather Station Hardware > Davis Instruments Weather Stations

The Reliability of the SHT-31 Humidity Sensor & What Psychrometer Should I Buy?

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jgentry:
I’m thinking about getting a sling psychrometer to make sure that my RH sensor is within specs. I would like to know which psychrometers are accurate and reliable.  Thanks!

miraculon:
I have used sling psychrometers in the past and broken them as well. I see one that is on Amazon that the thermometers seem to be protected. I don't know if it is good, bad or indifferent though. Most reviews are good, but there are some bad ones too. See: https://www.amazon.com/Bacharach-0012-7012-Spirit-Filled-Psychrometer/dp/B000LDNH8I

I found a used Belfort fan aspirated wet/dry bulb "Psychron" that I use occasionally to confirm the electronic humidity readings. I found it on eBay. There are some listed there currently. At least you aren't flinging breakable thermometers around with the fan, but make sure you getting a good one with functional thermometers and fan.

https://www.ebay.com/sch/12576/i.html?_from=R40&_nkw=psychron

Greg H.

ValentineWeather:
Not a sling, this unit has claimed better specs than most. 3% vs 5% humidity on most including sling types, probably because temperature accuracy is good at (+/-) 1°F.

http://www.extech.com/display/?id=14692

Listed $88 to around $100 depending on seller.


https://www.amazon.com/Extech-RH25-Heat-Index-Psychrometer/dp/B00DWX75QY/ref=sr_1_1?ie=UTF8&qid=1530708749&sr=8-1&keywords=Extech+RH25

DaleReid:
Valentine:
Have you seen one of these little gizmos?
I wonder if they are well built, have reproducible values and so on?

I've seen stuff like this at ham flea markets and some is a real find, other stuff is best bought by handling it for a feel of what it's like.

For this price is is no Vaisala probe, but may function pretty well for our use, especially after we get our stations installed and you want to wander over after a few months or change in season to see what it says compared to the station sensors.

As far as the little units with a fan on them, is that the 'original' FARS concept?

Just teasing.  But it makes sense.  I know our building guy would wonder around the halls with a sling unit and it was a bit daunting to see him whipping the thing around, (mercury) thermometers exposed and going 40 mph in circles. 

I assume it was correct as one could get with distilled water and doing it long enough to be stable.

Didn't Taylor make a twin yellow thermometer unit in a sling configuration, too?

Our lust for accuracy and precision are overwhelming when we get digital and start to see decimal points on a readout.  With a sling you'd need a table and do a little interpolation anyway.

Dale

miraculon:
By the way, the Psychron is (was) like a sling in that it has two mercury thermometers with 1 degree graduations.

I found some specs here: http://www.belfort-inst.com/Model_566.htm

The fan eliminates the need to "sling". The wet and dry bulb thermometers are terminated in a venturi-like housing and the fan draws the air across the two thermometer bulbs. I use distilled water with mine as recommended.

Greg H.

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