What is Thermo-Hygrometer?

Most are familiar with these instruments because if you have been to a hospital or even a mall these days, you can see it mounted in a wall. A thermo-hygrometer is an instrument used to measure and monitor temperature and humidity at a time, it is also known as Temperature Humidity Meter. It is a combination of a thermometer and a humidity meter or hygrometer.

Since both parameters affect each other, it is good that we can monitor them simultaneously. Some Thermo-hygrometers has a recorder included with a chart to properly display and monitor the readings. We are already familiar with a temperature which is the degree of hotness or coldness of a body or system, while humidity is the amount of moisture or water vapor in the air.

Why use a Thermo-hygrometer?

In our typical environment outside, when it is very hot and very humid, what do you feel? If you observed, you will perspire faster and that perspiration in your skin will not evaporate easily so you feel very sticky and uncomfortable. On the other hand, when it is very cold and low humid, our skin and lips are very dry, moreover, it also affects our breathing making our throats dry resulting in a cough.

But how do we know that temperature and humidity are low or high? It is through the use of a thermo-hygrometer.  By monitoring temperature and humidity, a desired environmental conditions can be controlled and achieved. Thermo-hygrometer will monitor the environment and inform us what needs to be done so as not to affect our equipment and our process.

The Importance of Thermo-Hygrometer

There were lots of reasons why during calibration, environmental conditions must be accepted before starting a calibration work.

In dimensional calibration, the temperature is a big factor in maintaining an accurate measuring process. A gauge block, for example, will be affected by thermal expansion and this will result in an additional source of error.

In electrical systems, the presence of high humidity can result in moisture in which some electrical components particularly made of metals will get rusty or oxidized which can result in damage or malfunction. 

On the other hand, an area environment with low humidity will cause high resistance in the air where a problem with the electrostatic discharge will be observed.

In some food industries, humidity is kept low to avoid molds from growing in their products and to maintain dryness and preserve its good quality. Others kept the temperature and humidity higher to grow bacteria to ferment their products.

And other applications that require humidity and temperature-controlled environments.

Where to use a Thermo-hygrometer?

Thermo-hygrometers are used especially in an area or room where temperature and humidity are critical in a process just like in laboratories, manufacturing areas, pharmaceuticals, food industries, and more. Critical in a way that it affects your process where continuous monitoring should be properly implemented. Some products or procedure also requires a certain temperature and humidity to be processed properly.

Why Calibrate a Thermo-hygrometer?

As for other instruments that are used for measuring, thermo-hygrometer should be calibrated to ensure accurate readings. Thermo-hygrometer has a sensor that can degrade and drift anytime so a regular calibration must be applied.

Some thermo-hygrometers or hygrometers can drift easily and cannot be adjusted. Once your Thermo hygrometer is calibrated, a calibration certificate will display the errors, and therefore, you can use it to apply corrections during measurements.

It is also advisable to monitor the performance by comparing it regularly to another calibrated thermo-hygrometer. This will ensure that drift can be detected immediately while it is within the calibration interval.

Regular calibration will also provide a good record for us to decide if we increase or decrease the calibration frequency we use.

A recommended calibration interval for thermo-hygrometers that are situated in a stable environment is 6 to 12 months.

How to calibrate a Thermo-hygrometer?

The standard way for a Thermo hygrometer and/or hygrometer calibration is to use a special chamber or a humidity generator, this is usually performed in a lab. The humidity generator can be varied to different ranges of humidity and temperature.But in this post, we will focus on a single range calibration and we will perform the calibration in the location where the thermo hygrometer is being used.

Thermo-hygrometers have different types of sensors, but regardless of the sensor types, the procedure for calibrating them is mostly the same. As long as the sensors are accessible and intact, we can calibrate it with this simple method.

This method can be applied for the hygrometer calibration procedure. It is only the humidity that is calibrated.

It is purely a comparison between a standard or more accurate Thermo-hygrometer and a regular thermo-hygrometer which we call a unit under calibration (UUC) where adjustment is not required unless the instruments have the capability to be adjusted.

You can use this method at any ambient room temperature in an enclosed area where the environment is stable. This method is suitable for those thermo-hygrometers that are permanently installed in a location where removing them is not possible.

Also, this method is applicable when you are not requiring a very high accuracy of results or you have a wide tolerance for your process monitoring.

Objective:

To define the verification procedure on thermo-hygrometers with a probe using a Fluke 971 as the reference standard. We will be using a single point calibration since the environment that we will measure is the existing environmental condition in a stable room.