How to Calibrate a Digital Thermometer

Lead Image
What You'll Need
Digital thermometer
Crushed ice
Boiling water
Small flat screwdriver

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

A pot of boiling water

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.