A good temperature and humidity sensor is a huge boon for proper building management and a number of other business ventures. Temperature AND humidity detection means that your heating and air conditioning units can compensate for those environmental factors that sneak up on you and add to your electric costs, for instance. In today’s article we are going to talk about how these devices work, the different types, what kind of applications they have, and even give you a few examples just in case you’d like to enhance your current building management and automation capabilities. Let’s talk about temperature and humidity sensors: 4 20MA output and more!
So, how do temperature and humidity sensors work?
We’re glad that you asked! Also known as a hygrometer, a sensor of this type detects moisture which is in the air along with its temperature. The reason for this is that you want to gauge relative humidity. Relative humidity is what you get when you compare the moisture in the air outside at the current temperature and compare it with the normal amount of moisture at a particular temperature. The sensor basically works by detecting changes in the air that affect the temperature or alter electrical currents. There are, however, three main types of sensors which we will now explain.
The 3 types of temperature humidity sensors
Temperature humidity sensors come in three types and we should explain a little about each in order to help prepare you should you decide that you wish to invest in one. The 3 types of temperature humidity sensors are as follows:
- Capacitive – Ideal for commercial, industrial, and weather applications, a capacitive sensor works by the means of a strip of metal oxide placed between two electrodes which allows you to measure relative humidity based on the conductivity of the strip. This is fairly accurate, with a range from 0 – 100%, with the caveat being that these are complex circuits and they will require regular calibration in order to remain accurate. Due to their high level of accuracy when they are kept calibrated, capacitive sensors are quite popular.
- Resistive – A resistive sensor works by the means of monitoring the ions in salts, to determine the impedance of the atoms present. With the changes in humidity more or less resistance is detected from the electrodes working with the salt medium, allowing for temperature and humidity assessment.
- Thermal – A thermal sensor incorporates two sensors which are housed differently, with one in a medium of dry nitrogen while the other is by itself and measuring the ambient air. By the differences in what each sensor detects the relative humidity may be determined.
Applications of temperature humidity sensors
There are many applications for temperature humidity sensors. Building management, industrial, and commercial, being able to gauge the relative humidity not only ensures comfort but it can be integrated for proper care of materials as well. Textile is a good example. For instance, cotton has a high relative humidity of 70% to 80% due to its brittle nature. White silk, by contrast, is better at 65% to 70%. With a temperature humidity sensor you have the ability to not only detect the temperature and humidity of a room but you can also control it.
Some example sensors
We’ve included some sample temperature humidity sensors for you to take a look at. They come from a company called Dwyer, which has been around since 1931 and they hold over 650 design patents. This means that you can take advantage of their expertise for your own building management, industrial, or commercial usage. Let’s take a look at a few of their models.
Model 657-1 Relative Humidity/Temperature Transmitter
The Model 657-1 provides two 4 mA channels in order to produce 2 separate output signals, one for
“These are fairly accurate, producing a +1 degree Fahrenheit on temperature readings”
humidity and one for temperature. These are fairly accurate, producing a +1 degree Fahrenheit on temperature readings as well as a +2% accuracy when it comes to humidity. The units may be installed with ease inside the ductwork of your buildings and are excellent for HVAC or Cleanroom monitoring.
Series RHP-E/N Wall Mount Humidity/Temperature/Dew Point Transmitter
The RHP-EN is an excellent temperature and humidity sensor and considered one of the most versatile around. While it looks smooth and stylish, it is actually quite well ventilated in order to better ensure its measurement accuracy. It measures the dew point and humidity by the meaqns of a capacitive polymer sensor that can recover from 100% saturation. The optional temperature output can voltage, current, thermistor, or RTD, while the humidity or dew point can have a voltage output. With the voltage and current outputs the temperature range is going
to be field selectable.
Series RHP Humidity/Temperature Transmitter
The series RHP is a model which combines the current humidity transmitters output, RTD output, or the voltage. Employing polymer capacitance humidity sensors you can enjoy, depending on the model you select, and accuracy of 2%, 3%, or 5%. An optional 2 line alphanumeric display is available, but not necessary, and these units are duct mountable if that’s what you need. It should be noted, if you intend to mount this in a duct near to cooling and fan coils then you will want to obtain the sintered filter option for best results.
Some final words on temperature humidity sensors
In this article we have discussed the ins and outs of temperature humidity sensors. Starting with how they work, the three types, applications, and examples. If you are currently managing a business or a building, these are definitely worth considering, as tight environmental control not only ensures the lifespan of products produced by your businesses as well as the storage period of the materials but it can also save you lots of money. For best results, contact your vendor with your building’s requirements and any special requirements that may involve materials or people and they should be able to let you know how many sensors you will need to take advantage and save yourself a little cash!