Hi, we have a thermohygrometer which charts our environmental conditions. Our calibration laboratory temperature is controlled at 21±3°C. Question: Is it acceptable to have the thermohygrometer calibrated at only one point (ie. 21°C), or does the calibration requires any minimum set of points (eg. 18°, 21°, 24°). Thanks.

Hi, we have a thermohygrometer which charts our environmental conditions. Our cal lab temperature is controlled at 21±3°C. Question: Is it acceptable to have the thermohygrometer calibrated at only one point (ie. 21°C), or does the calibration requires any minimum set of points (eg. 18°, 21°, 24°). Thanks.

I would recommend to go for a 3 point calibration.

Additionally, visit your city statistics information for the highest and lowest values of temp and humidity and accordingly select the high, low and optimum value for calibration.

So, you could use this thermohygrometer in any area within your facility.

As a metrologist, I have oft been quoted as saying "3 points is a cal." So I would concur with that recommendation.

However, it is not uncommon or unacceptable to do a one point cal. Some brand names of hygrometers in their OEM procedures even give you the option of single point or a variety of multi-point cals.

Whether it is acceptable or not may be a factor of your quality policy. It is a cost/convenience saving to do a single point cal, and may be satisfactory.

However, if you ever have an excursion away from your single point, you have no way to know how accurate your hygrometer (hygrothermograph) is.

What is going to happen if your calibration labratory falls to 17 C or rises to25C? If the answer is everything needs to stop while it is sorted out you probably want a multi point calibration. If all that is going to happen is an employee goes "brrr...I'm cold" then you could probably get away with a less rigourous calibration.

Often, a cal lab may cal that type instrument at 50% and 23 C.

I recommend at least two points, three is preferred.....and for RH you low and high end of what you monitor, and one in the middle.....

One other point, make sure to get the uncertainties, and not just a pass/fail.....

Hershal

THANKS to ALL for your replies. I am now convinced we'll need a 3 cal points for thermohygrographs in our lab.

PS. I hope no one will feel I'm using the "Thanks" too indiscriminately!!

PS. I hope no one will feel I'm using the "Thanks" too indiscriminately!!

Not at all, thats an appreciaition for the valuable inputs which we get in this Cove.

Qualityalways is correct.....our hope is to help you succeed.

Hershal