Our clients often ask: "I have located a few thermometers and temperature meters in the same room but they show different temperatures. Which devices or thermometers should we believe? “
In any room there exist certain temperature gradients, even without ventilation. Within two meters horizontal temperature gradient may be 2°C, but a temperature difference between the floor and the ceiling may consist up to 10°C. Therefore, the difference in a few degrees of the readings within the room is not an indicator of equipment malfunction.
But nevertheless if there are doubts one should perform the calibration test or at least checking of measuring instruments.
The procedure of calibration is operating tests with the purpose of confirming instrument accuracy. Each measuring tool should be calibrated before it is shipped out. Usually one year of calibration period is specified in the certificate. So, to be sure in correct measurements, thermometers should be checked in the Regional State Standard laboratory once a year, where specialists will confirm the correctness of metrology measurements or recognize them unusable.
It is clear that all temperature instruments used by mushroom growers are hardly possible to calibrate in the State Standard laboratories. We recommend you to select for at least one thermometer or temperature indicator (the most accurate of those that you have) and calibrate it every year. Such a standard precision instrument will allow the mushroom growers periodically to check the correct operation of all means of temperature measurements by their own.
Measuring instruments can be checked by comparison. You will have to pour water in any container and leave the containter, sensors and metallic open thermos in the place where they will be compared through a few hours so that the water and the thermos wall will accept room temperature (picture1). Pour the water in the thermos and immerse sensors and thermometers into it (picture 2). Hold it for at least half an hour. After that, we can assume that the unevenness of the water temperature in the thermos will be less than 0.2°C and it can be possible to compare the indications. The indications of devices and thermometers should be compared with the indication of the standard precision thermometer.
If the difference between the indications of the device and the standard precision thermometer differ by no more than the sum of errors plus 0.2°C, it means that devices and thermometers measure correctly.
If you find that any of the glass thermometers indicate incorrectly it cannot be used anymore.
If you find the wrong indicating of any sensor or measuring instrument, it should be calibrated in the State Standard laboratory. The specialists will measure the exact deviation from the true value and amend the device. After that the instrument will once again show correctly.