A digital thermometer should always return accurate readings. Whether you use it for cooking, for measuring body temperature, atmospheric temperature, or any other relevant use, a thermometer should always be made to provide the correct temperature. From time to time, digital thermometers will require recalibrating. This is, fortunately, a very simple task. Here are some easy steps to follow.
Step 1 – Know When to Calibrate
You will want to calibrate the thermometer before you use it for the first time to ensure that a thermometer reads the correct temperature before you need it for any readings. It also needs calibration when dropped since the impact may affect its ability to read correctly. It is also recommended that you calibrate a thermometer when it is used to measure extreme temperatures. Measuring very hot and very cold objects may cause slight errors the next time you go to test something. Finally, thermometers require regular calibration (daily or weekly) when they are used frequently.
Step 2 – Test Your Thermometer
Use these two methods to get your thermometer back on the right track. The first is the freezing point method. Fill a glass with crushed ice. Add a little clean water until the glass is full and stir. Wait for about three minutes before inserting the sensor on the thermometer into the ice-filled water. Wait for about thirty seconds and check that the thermometer reads 32°F. If it does, then it is accurate, but if not, it requires calibration. This is by far the most accurate method, and it will also give you an idea of how far off your readings are when it comes time to reset it.
Another method is called the boiling point method. You need to boil about six inches of water. When the water reaches its boiling point, place the sensor into the water and make sure that you keep it as close to the center as possible, away from the sides and bottom of the container. Wait for thirty seconds and check if the thermometer reads correctly at 212°F if you are at sea level or below 1,000 feet elevation. The boiling point of water will vary for different elevations: sea level at 212°F, 1000 feet at 210°F, 2000 feet at 208°F, 3000 feet at 206.4°F, 5000 feet at 202.75°F, and 8,000 feet at 197.5°F.
Step 3 – Calibrate the Digital Thermometer
Adjust the nut or the slotted fine adjust potentiometer of the digital thermometer in order to correct the temperature as needed. This is done by simply turning the adjuster until an accurate reading is reached. Some digital thermometers do not require any adjustment of a screw or nut. You simply need to locate the reset button. When the freezing point or boiling point of water is achieved, push or hold the button and that’s it.
Since a single-point test can only ensure that your thermometer is correctly calibrated for one temperature, it is best to conduct at least two different tests using the measuring points above for the most accurate calibration.
Calibrate a Digital Thermometer FAQ
Why is my digital thermometer inaccurate?
Digital thermometers are truly modern marvels. They are incredibly handy little gadgets and super convenient but they are not always perfectly accurate.
Many different variables can affect the accuracy of a digital thermometer, including radiant heat, direct sunlight and a simple draft of air. If the thermometer is used on a person who has been wearing a head wrap, a headband or a hairpiece, or even if they have sweat or dirt on their forehead, the reading may also be inaccurate.
Inaccurate readings can also indicate that the probe itself on the thermometer is wearing out, or could indicate that the battery is dead or losing strength. Sometimes, the thermometer simply needs to be reset and will display incorrect readings until this is done.
How do I make sure my digital thermometer is accurate?
If you don't know your digital thermometer is accurate, it's pretty difficult to judge whether or not you have a fever. Test the thermometer's reading by making a glass of ice water.
Swirl the ice around for a few moments to get the water uniformly cold and place the thermometer in the water in the glass for about 30 seconds. Don't touch the bottom or sides of the glass with the thermometer.
The thermometer should read 32 degrees F, which is freezing temperature. If it does not, you can now seriously doubt the accuracy of the device.
Can you reset a digital thermometer?
If your digital thermometer is giving incorrect readings, there are a couple of ways you can reset it.
Place the thermometer in ice water, which should give a temperature reading of 32 degrees F. If the thermometer has a dial, adjust this by turning the hex nut until the temperature does read 32 degrees.
Most of the time, the thermometer will have a reset button. Press and hold this while the thermometer is in the water and it should now read an accurate 32 degrees.
If there is no reset button, try replacing the battery and then test the temperature in the ice water to see if the reading is now correct.
What happens if you don't calibrate a thermometer?
Over time and with use, thermometers can "drift," meaning they may start to vary by a degree or more in their readings. Calibrating thermometers ensures that readings remain accurate, which makes calibration an important maintenance step.
Can you make a digital thermometer read higher?
Digital thermometers can be tweaked a bit intentionally to display readings that are slightly lower or higher. For example, you can hold it very tightly in your hand to make it read higher than body temperature because the palm of the hand can get very hot and sweaty without air.
Taking a drink of something hot or cold and then putting the thermometer in your mouth will also skew the reading. Even wearing a hat can affect the accuracy of the reading, sometimes.