Bair Hugger Model 775 Operating Temperature Calibration
Temperature Modes: The warming unit has four operating modes: Ambient, 32°C, 38°C, and 43°C. To select the 32°C, 38°C, 43°C, or Ambient mode, press the corresponding button. The warming unit will operate within the specified temperature range.
Alternative Modes
The warming unit has five alternative modes that allow access to the service and calibration utilities of the warming unit (see Figure 1).
AltMode0 – Hour Meter
AltMode1 – Calibration
AltMode2 – Fault Code
LogAltMode3 – System Information
AltMode4 – Over-temperature Detection Test
Figure 1 Alternate modes
Figure 1 shows how to access alternative modes by pressing Alt mode 0 and the Ambient button (Altmode1 Calibration) simultaneously for 3 secs, allowing you to go into calibration mode.
The temperature management system needs to be calibrated every six months or after 500 Hours of operation, and the filter needs to be replaced after every 500 Hours of operation.
Test equipment – Model 22110 Temperature test unit. Connect this test device with a Fluke model 52k/J Thermometer.
Calibration Steps Involved:
If the warming unit has been stored at a temperature lower than 20°C, allow it to reach ambient temperature before the calibration procedure begins.
1. Attach the Model 22110 temperature test unit to the end of the warming unit hose.
2. Connect the warming unit to a grounded power source. The warming unit performs a self-test and automatically proceeds to Standby mode.
3. Press the Ambient button to place the warming unit in Ambient mode. Allow the warming unit to run in Ambient mode for at least ten minutes to equalize the temperature of the warming unit’s internal components.
Note: Verify warming unit is set to a high fan setting by ensuring the indicator light next to the upper fan is illuminated.
4. Press the Alternative Mode button (see Figure 2. Location of Alternative Mode button on page 7) and the Ambient button simultaneously for 3 seconds. The warming unit is now in Calibration mode. In this mode, the warming unit performs the following tasks:
• 32°C and 38°C indicator lights flash, indicating they can be used to adjust the offset value.
• Blower remains on.
• Heater elements remain off.
• The text TMP and the end of hose temperature in °C (0.1°C resolution) appear in the alphanumeric display.
• The text OS and the current calibration offset value (0.1°C resolution) appear in the alphanumeric display. 5. Compare the temperature shown on the alphanumeric display and the temperature shown on the thermocouple monitor.
• If the temperatures match, no adjustment is necessary; press the Alternative Mode button to return the warming unit to Standby mode.
• If the temperatures do not match, adjust the warming unit displayed temperature: a. Press the 32°C button to decrease the temperature or the 38°C button to increase the temperature by 0.1°C. You can adjust the temperature of the warming unit to a maximum of ±3°C. b. Continue to press the 32°C or 38°C button(s) until the temperature in the alphanumeric display matches the temperature on the thermocouple monitor as close as possible.
c. Press the Alternative Mode button to store the calibration offset value and return the warming unit to Standby mode.
Reference: Model 775 Service Manual (3m.com)