We normally trust readings of instrument at hand, don't we? Better than a wild guess, right?
I have 2 household type temperature/hygrometer units purchased over time. The unit (on right) was my first purchase for over a year now. I bought the unit (on left) as it has additional external temp sensor.. useful to monitor both internal & external temp. But it never occur to compare their readings until now. Temperature readings are pretty close but a 18% difference in reading! Which would you trust?
As I am building my own humidifier controllers recently, I gathered all my other instruments together and get more surprises! I also bought a hand-held unit and several hygrostats. Put them all together I get 4 different readings! The spread is 22.5%! Wow.. which do I trust now?
The later two are instrument grade products. I bought the hand-held unit for its fast response to humidity changes (and the most expensive of course). Shall I trust it more?
Another factor that compounded the issue further, differences in reading varies over time. Question of linearity amongst them varies too!
My object here is to open up your mind as to what you can expect with your instruments too!
Fortunately for the moment, I can resolved the situation with the 4 hygrostats that tracks with each other within 1% over time. As for the hand-held unit, I would take it back to the shop and check its accuracy against other units.
From my experience in the electronics industry, I would only trust instrument grade products from the industry. Consumer grade product companies are too cost driven in their designs that compromise product quality (both in design & production). They may lack quality assurance in precision of the sensors used.
Lesson here is to check on the company that manufactured the hygrostats - see if they have good R&D capability.
3 comments:
I do have 2 sets of industrial grade humidifier. It is used to check the humidity in the chamber. I also bought a data logger that able to log the temp and humidify over a period of time. The data logger from US. I will use them to compare the temp and humidity results at my new BH.
Hey Gee, we can compare the readings of our instruments next week too. I brought back my hand held unit.
calibrate them first. then see if there's significant drift afterwards or if the calibration has drifted.
some details of creating a known humidity environment to calibrate the devices is here.
http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/momo/momo_002.cfm
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