There are many situations in which a temperature measurement is needed, and there is an equally wide variety of thermometers on the market. It is important to choose the right thermometer for your needs to ensure efficiency and accuracy. There are two main uses for thermometers: industrial and medical. Let’s go into the types of thermometers, advantages and disadvantages of each, and other factors you should consider before you buy.
Thermometers have many uses in industrial settings. From HVAC to food to agricultural, there are several jobs that require frequent temperature readings. Some situations require an internal temperature measurement, while others can only get a surface measurement. Before you buy an industrial thermometer, you should consider the setting in which you are measuring and make sure your thermometer is the best fit to get the right measurement.
Digital Probe Thermometers:
Digital probe thermometers use a probe that is inserted directly into the object being measured. They are ideal for when you need to know the internal temperature of something such as an air duct.
Pros of digital probe thermometer:
- Accurate readings
- Measures internal temperature
- Small size makes it easy to carry and transport
Cons of digital probe thermometer:
- Requires direct contact with objects and items that are fragile, dangerous, or out of reach (ex: computer circuitry, molten metal, moving conveyor belts)
General Purpose Infrared Thermometers:
General purpose infrared thermometers are great for situations where you are unable to directly contact the object you are measuring. They are gun-shaped and take measurements by using lasers to point at the surface. The pros of this type are the same as the cons of probe thermometers: they can measure those objects that cannot be measured using direct contact.
Pros of general-purpose infrared thermometer:
- No-contact option is safer
- Take quick measurements
- Can measure a wide range of temperatures
Cons of general-purpose infrared thermometer:
- Not as accurate as contact measurements
- Do not measure all surfaces equally (ex: shiny metals are harder to measure)
- Cannot take internal measurements
Can I use a general-purpose infrared thermometer to check my body temperature?
The surface of the forehead does not exactly match the internal body temperature, so infrared forehead thermometers, also known as temporal artery thermometers, make calculations to match the forehead surface temperature to the internal body temperature. If you use a regular thermometer to measure your forehead, you are losing that calculation and you will get a temperature that is lower than your actual body temperature.
If you have no other choice but to use a general-purpose infrared thermometer to take your temperature, there are a few ways to combat these differences. If your thermometer has adjustable emissivity, you can set it to 0.78. If you are using fixed emissivity, you can add 5 degrees to your forehead temperature. You could also just accept a reading of 91F-95F as normal temperature, and anything higher than that as a fever. This is because the surface of your forehead is about 5 degrees lower than your internal body temperature.
Some thermometers use thermocouples as their heat sensors. A thermocouple is made up of two wires welded together. A k-type thermometer is named for its k-type thermocouple, which is the most common type of thermocouple.
Pros of K-type thermometer:
- Good resistance against oxidation
- Measures a variety of temperatures
Cons of K-type thermometer:
- Less accurate than other types
- Susceptible to corrosion
Other factors to consider:
No matter what type of thermometer you choose, there are some important factors that you need to consider before you buy:
Emissivity for infrared thermometers:
- Definition of emissivity: measurement of a material’s ability to emit infrared energy
- Shiny metals have lower emissivity rates and are more likely to emit the energy of the substances around them than their own energy, making measurements inaccurate
- Thermometers have either adjustable or fixed emissivity
- Choose one with adjustable emissivity if you will be measuring surfaces with different emissivity levels
Distance to spot ratio/optical resolution for infrared thermometers:
- Distance to spot ratio is the circle of the measurement zone
- The laser points at the zone, while the thermometer measures from a distance around it
- Example: if the distance to spot ratio is 12:1, the distance it measures is 12 inches away from the 1-inch measurement zone
- If you will be outdoors or dealing with extreme temperatures, you need to make sure to get a weatherproof thermometer that will withstand those conditions
- Make sure you know the range of temperatures that you will be measuring
- Some have high and low temperature limits with alarms that you can set to sound when the limit is reached
- If you are going to use your thermometer often, make sure you choose one with a long battery life
- Some also have auto shut off to save battery
A fever is a leading symptom of many types of illnesses, including COVID-19. As businesses begin to reopen, many are requiring mandatory temperature checks for employees. It is important to choose not only the most accurate thermometer, but the safest and most efficient for your situation.
Regular digital thermometers are the most common type of thermometer and can take temperatures through the rectum, mouth, or armpit.
Pros of a regular digital thermometer:
- Take temperature quickly
- Most accurate readings of all medical thermometer types
Cons of regular digital thermometer:
- Must be cleaned after every use
- Food, drink, and exercise can interfere with the reading
Ear thermometers are inserted into the ear and use an infrared ray to measure temperature inside the ear canal.
Pros of ear thermometers:
- Quick measurements
- Easy to take temperature
Cons of ear thermometers:
- Earwax can interfere
- Readings are not as accurate as regular digital thermometers because of interference
Forehead thermometers use an infrared ray to measure temperature of the surface of the forehead. The thermometer then converts this into internal body temperature. Some require the thermometer to touch the surface of the forehead to take a measurement, while others can do it a few inches away from the forehead.
Pros of forehead thermometers:
- Quick readings
- Safe no-contact option makes it efficient for businesses testing employees
- Comfortable because it requires little to no contact
Cons of forehead thermometers:
- Expensive compared to other types of thermometers
- Not as accurate readings as digital thermometers because the forehead surface does not exactly match internal body temperature