Guide to Digital Thermometers

Buying a digital thermometer can be sometime a difficult task. There are plenty of choices readily available, with prices starting from just a few dollars to thousands of dollars. So, which one of these digital devices is best for you? what are different types of digital thermometers available? How can you keep costs minimal without compromising quality or standard?

Finding the Perfect Digital Thermometer

As there is no device which is perfect, there will be compromises that we have to make, and every devices will have its good points and its bad points. The same holds true for digital thermometers too. Each type of device has it’s limitations, whether it be cost, reliability, ease of use, or accuracy. The key is to find the best solution that meets your requirement while reducing the risk of error and keeping costs low. Also we must understand that digital thermometers has limitations, so that any potential for inaccuracies can be accounted for or avoided.

Understanding Digital Thermometer

Digital Thermometers are replacing the conventional mercury thermometer due to the ease of taking reading and also because Mercury thermometers poses health and safety problems. Digital thermometer is much more advanced in construction and material composition than mercury or liquid in glass thermometers, it can be broken into two primary components: a sensing element, and readout device or CPU. The type of materials used in the sensing element determines the type of device.

The use of modern computing technology allows for digital thermometers to do much more than simply measure and display a temperature. Digital thermometers are now available with a plenty of features and tools, such as recording the change in temperature over a time interval, or sounding an alarm when a desired temperature is reached. Many digital thermometers can be connected to an external computer where temperature data can be used for further analysis.

Types of Digital Thermometer

Thermistors
Thermistors are made of ceramic materials formulated from metallic oxides. Thermistors are generally calibrated and suitable for a small temperature range. if you are looking for great accuracy and fast response time at a less price, then thermistors are best for you. But, their limited range of use makes them suitable only for measurements near room temperature. If you are buying thermistors, be sure to double-check that the device you’d like to buy will work effectively in the temperature range that you expect to use it in. Also importantly note that bead-in-glass thermistors offer greater stability compare to disc-type elements.

Thermocouples
Thermocouples are composed of two wires, which are made of a different material. The wires are joined at two points, or junctions. One of the junctions is designated as the measurement junction, and the other as the reference junction. When the measurement junction is exposed to a temperature that differs from that of the reference junction, electrical current flows through the circuit. The voltage difference between the two junctions can be measured and converted into temperature.
Thermocouples is a versatile device and are widely used for temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. They are less expensive but are not suitable for applications where smaller temperature differences need to be measured with high accuracy. Thermocouples should only be used when one or more degrees of error in temperature measurement is acceptable.

Infrared Thermometers
Infrared (IR) thermometers sense heat in the form of infrared energy. The optic mechanism inside an infrared thermometer collects the energy emitted by an object and sends it to an infrared detector. The detector then transforms the energy into an electrical signal, which is then shown on the display. For more information on Infrared thermometer check Infrared Thermometer and its Application.
Infrared thermometers offer a non contact method of temperature measurement, and can only be used to measure surface temperature. These thermometers are less accurate as compare to thermistors or thermocouples especially for uneven surfaces. They are recommended to use to measure temperature for flat and smooth surfaces.

Type of Device Cost Accuracy Durability Range Pros Cons
Thermistors $200 to $2000 0.01 to 0.1ºC

Good

-5ºC to 90ºC
  • Great Accuracy
  • Rugged
  • Limited Range of use
Thermocouples $100 to $1000 Over 1ºC

Great

-200ºC to 1800ºC
  • Low Cost
  • Rugged
  • Problems with Accuracy
  • Readings tend to drift
Infrared $30 to $200 Over 2ºC

Fair

-50ºC to 1100ºF
  • Low Cost
  • Non Contact measurement
  • Problems with Accuracy

Leave a Comment

Current month ye@r day *