Is Joule not reporting the water temperatures you’re expecting? If Joule's circulation chamber has become dirty or scaled, it can affect the detected water temperature. So, before doing any of the calibration testing, please clean Joule via the following instructions:
Joule uses a thermistor that is capable of +/- 0.1 ºC, or +/- 0.2 ºF, accuracy. Each unit is tested multiple times during manufacture to ensure that your Joule is of the highest accuracy out of the box. To help us determine if you have received a Joule that might be inaccurate, the following test and test method should be employed.
Please calibrate your reference thermometer per manufacturer instructions and record the calibration measurements. Typically, you will perform an ice bath calibration at 32 ºF/0 ºC and a boiling calibration corrected for atmospheric pressure.
You may also use Joule without running the motor in these calibrations. Just put Joule into the water and record the temperature that is displayed on the App screen. In all cases, you will need to manually stir Joule like you would with a spoon or spatula to ensure that it reaches an equilibrium point. If you do not, the temperature that Joule will read may be slightly higher than the true water temperature.
How to carefully compare Joule temperatures:
- Set up the water with approximately 8 liters, or 2.1 gallons, of water. For best results, use a vessel that has well-insulated sides. Covering the sides with a towel will work well. You do not need a lid for this test.
- Place Joule on one side of the vessel and aim the water outlet so that it shoots across the center of the bath.
- Set Joule to a temperature of 104° F / 40° C.
- After the water has reached the set temperature, allow Joule to circulate for at least 20 minutes undisturbed.
- Place your reference thermometer about 2 to 3 inches to one side of the water outlet and record the temperature. The water coming out of the water outlet is being heated, so it will be warmer than the set temperature. You’ll want to be careful not to measure the temperature of this water.
- Compare this recorded temperature to the temperature in the Joule app.
- Repeat steps 3 through 6 for 158° F / 70° C.
- If you have access to multiple reference thermometers, please repeat these tests with each one. (More data is better!)
To note, here are things that can affect the temperature read by a reference thermometer:
- The size of the container, how well insulated it is, the temperature of the cook, how long the water has been circulating, and the position of the reference thermometer within the container compared to the position of Joule. You may want also to try placing your reference thermometer in different positions within the water to gather a range of temps to compare.
If the tested temperatures are significantly different than your calibrated reference thermometer, please make a table of your measurements—including the thermometer calibration data—and send it to us via a support request by clicking the link below.