Resolving my hygrostats readings - Part 2

With a doubt about its accuracy, I took my hand-held unit back to the shop for comparison. I was attended by the manager. He was surprised I thought the unit inaccurate compared to the hygrostats (both bought from them).

The sensor used is 'thin-film' technology and should be more accurate he said.
But I got all 4 hygrostats track each other within 1% and reading 9% lower from the hand-held unit, I informed.

Without fuss he had the show room unit side by side with mine. After a few minutes, the reading differences between the 2 units was 1.3%! What can I say now!

Today, I went back with my camera to repeat the tests again. This time I was attended by an executive; the results was repeatable.

After a few minutes, the readings converged to 1.5% from each other.















A bit later difference was down to 1.2%.















Waited for another 5 min, it was still 1.2%.















Well, I am satisfied now.

The hygrostats actually has an offset adjustment of +/- 9%. So reading can be set to the hand-held unit as reference.

I also learned the accuracy of hygrostats sensor do drift with time and can be affected by environmental dusts, chemical pollutants etc.

So it is advisable to check their accuracy from time to time. For a start I will check them at 3-month interval and then to 6-month interval if sensors are still good.

Finally I would recommend when buying hygrostats, choose a brand that has replacement sensors.

Another word of caution, avoid blowing into the sensor (thin film type especially) to check its sensitivity. Just wrap your palm around and the humidity should go up in quick response; or place close to a glass of ice water and humidity should drop.