How-To Guide :: Soft Serve :: Temperature Calibration
Most Spaceman Soft Serve machines have digital controls and utilize PT100 temperature probes to measure the temperature in the hoppers and cylinders. The control board uses these temperature readings to control the cooling to the hoppers during freeze or standby modes, and to the cylinders in standby mode. The cylinder temperature readings are also used to protect the machine from too cold of temperatures or over-freezing. For more information on this protection, see the STOP 1 Error article.
Note: This article does not apply to the Model SM-6210, SM-6218, or any other analog Spaceman soft-serve freezers.
Often, these temperature probe readings may drift from the actual temperature of the product in the hopper or cylinder. This is completely normal since the temperature probes are not touching the product, but rather measuring the temperature through the stainless-steel hopper shell or cylinder wall. It may be required from time to time to adjust these temperatures in the digital controls in order to account for an offset such that the actual temperature of the product matches what is being read by the control system. The following process is best performed in the morning after cleaning the machine and allowing it to sit at ambient room temperature for several hours.
Special Note: The cylinder temperature does NOT control the viscosity of the frozen product. It is only used during standby mode and to protect the machine from over-freezing.
Alert: There is one temperature probe for each hopper and cylinder. In multi-flavor machines, there is only one refrigeration system for all hoppers. Each control board can call for hopper cooling, so it is very important that the temperature and fill levels of every hopper remains approximately equal. If you fill one hopper with warm product, and one with cold product, the temperature probe measuring the warm product will call for cooling, however, both hoppers will be cooled as there is only one refrigeration system. This could lead to the side with cold product over-cooling and freezing up. For this reason, Spaceman recommends filling hoppers only with pre-chilled product, and keeping hopper levels between the two sides as close to the same fill level as possible.
Testing Temperature Probes
Prior to calibrating, you should test the functionality of your temperature probes to ensure they are not too far out of calibration. In these cases, the temperature probe should be replaced prior to calibration. Spaceman sells replacement temperature probes at PartsTown. The Temperature Probe part number for digital soft-serve machines is: 3.1.02.13.020
- Often, the machine will detect when a temperature probe needs replacing and display a STOP 4 error code. For more information, see the STOP 4 Error article.
- To test if the product is too far out of calibration, use a food-grade thermometer to measure the product in the hopper or some recently dispensed product from the cylinder.
- Press the ‘P’ button on your machine to display the Temperature parameters being read by the control board.
- If the actual temperature and displayed temperature are different by more than 20 degrees F for either the hopper or cylinder, your temperature probe is likely too far out of calibration and needs to be replaced.
Calibrating Temperature Probes
- Follow the instructions in the Machine Manual or Cleaning Guide to drain, rinse, disassemble, and clean the machine.
- Follow the instructions in the Machine Manual or Cleaning Guide to assemble and lubricate the machine and all parts
- Fill the hopper and cylinder completely with room temperature water.
Note: It is best if the water has been allowed to sit at room temperature for several hours to stabilize the temperature. This will give you the most accurate results.
- Open the prime plug to purge all air and fill the cylinder completely.
- Allow the water to stand in the machine for several minutes, and allow the displayed temperature on the machine to stabilize.
Note: If the machine was recently in FREEZE or STANDBY modes, it is highly recommended to wait at least 30 minutes or longer to allow the system temperatures to stabilize.
- Turn the machine power on and put the machine in WASH mode for 1 minute
- Press the “P” button and write down the temperature displayed for the hopper and cylinder. These temperatures are the Temp_Hop_Reported and Temp_Cyl_Reported in the following equations.
- Example: Temp_Hop_Reported = 84.2°F (29.0°C), Temp_Cyl_Reported = 75.9°F (24.4°C)
- Using a food quality thermometer, measure the hopper temperature in three areas:
- At the rear, middle of the hopper, 1” from the back, and 1” below the product surface
- In the center of the hopper, 1” below the product surface
- At the front, middle of the hopper, 1” from the front, and 1” from the bottom
- Example: Temp 1 = 78.1°F (25.6°C), Temp 2 = 77.9°F (25.5°C), Temp 3 = 77.5°F (25.3°C)
- Average the 3 temperatures measured in the hopper, this temperature is the Temp-Hop-Measured
- Example: Temp_Hop_Measured = (78.1 + 77.9 + 77.5) / 3 = 77.8°F (25.4°C)
- Dispense 10-12oz of the water in the cylinder into a room temperature plastic cup
- Using a food quality thermometer, measure the temperature of the water in the center of the cup. This temperature is the Temp_Cyl_Measured
- Example: Temp_Cyl_Measured = 79.1°F (26.5°C)
- Calculate the following Hopper Adjustment:
- Temp_Hop_Adjustment = Temp_Hop_Measured – Temp_Hop_Reported
- Example: Temp_Hop_Adjustment = 78.1°F - 84.2°F = -6.3°F (-3.5°C)
- Calculate the following Cylinder Adjustment:
- Temp_Cyl_Adjustment = Temp_Cyl_Measured – Temp_Cyl_Reported
- Example: Temp_Cyl_Adjustment = 79.1°F - 75.9°F = 3.2°F (1.8°C)
- Press RESET to stop the machine
- Press and hold the RESET button to enter the programming settings
- Press RESET until you reach the Password screen, the password is 0-7-1-8
- Enter the password using the STANDBY and P buttons to increase or decrease the number and the FREEZE button to move the cursor forward
- Press the bottom middle button to access the advanced settings
- Press the RESET button until you reach the HOP.OFFEST setting
- Use the STANDBY and P buttons to increase or decrease the setting by the Temp_Hop_Adjustment value calculated in Step 12
- Example: If old Offset value was 7.3°F, and the Temp_Hop_Adjustment value is -6.3°F, decrease the 7.3°F value down to 1.0°F.
- Press the RESET button until you reach the CYL.OFFSET
- Use the STANDBY and P buttons to increase or decrease the setting by the Temp_Cyl_Adjustment value calculated in Step 13
- Example: If old Offset value was 1.6°F, and the Temp_Cyl_Adjustment value is 3.2°F, increase the 1.6°F value up to 4.8°F
- Press and hold the bottom middle button to save the settings
- Put the machine in WASH, wait 1 minute
- Press the P button to display the temperatures
- The temperatures displayed should match the average temperatures measured from the hopper above within 0.5°
- If the temperatures do not match within 0.5° repeat steps 5-21
- Repeat this process for all flavors on the machine
Resetting the Mix Temperature Setting
Often, operators will adjust the Mix Temperature setting to account for temperature offsets rather than properly adjust the offsets. Once your temperature probes are calibrated, it is important to reset the Mix Temperature setting so that the product in the hoppers does not freeze up or exceed food safe temperatures. This setting should almost always be left at 39°F (3.9°C).
- Press and hold RESET to enter the programming settings
- Press RESET until you reach the MIX TEMPERATURE screen
- Use the STANDBY and P buttons to adjust this setting to 39.0°F (3.9°C)
- Press and hold the bottom middle button to save the settings
- The machine can be returned to normal use