What is the reason for the inconsistency between the measured temperature and the actual temperature of the laboratory rotary tube furnace?

The inconsistency between the measured temperature and the actual temperature of the laboratory rotary tube furnace may be caused by various reasons, including:

1. Temperature sensor related issues
Improper sensor position
Reason: If the temperature sensor is not placed in a position that can accurately reflect the average temperature inside the furnace, such as near heating elements or furnace doors where there is a large temperature gradient, it will result in a deviation between the measured temperature and the actual temperature.
Example: The sensor is closely attached to the heating zone of the furnace tube, and the measured temperature is too high; If placed at the cold end of the furnace tube, the measured temperature will be too low.
Sensor aging or damage
Reason: Long term high temperature environment may cause sensor performance degradation or measurement distortion due to physical damage.
Testing method: Use a standard thermometer for comparative measurement, or calibrate the sensor regularly.
Sensor response delay
Reason: The sensor’s response speed to temperature changes is insufficient, resulting in a delay in dynamic measurement compared to actual temperature changes.
Impact: During rapid heating or cooling, there is a significant difference between the measured value and the actual value.

2. Thermocouple or compensation wire issues
Thermocouple material mismatch
Reason: The thermocouple material does not match the compensation wire material, resulting in inaccurate cold end compensation.
Impact: Systematic deviation in temperature measurement.
Compensation wire fault
Reason: Compensation wire insulation damage, poor contact, or electromagnetic interference can cause signal transmission distortion.
Testing method: Check the appearance of the wire, measure the resistance value, and eliminate electromagnetic interference sources.

3. Temperature control system issue
Improper PID parameter settings
Reason: PID controller parameters (proportional, integral, derivative) were not optimized, resulting in unstable or overshoot temperature control.
Impact: The measured temperature fluctuates greatly and deviates significantly from the set value.
Calibration deviation of temperature controller
Reason: The temperature controller has not been regularly calibrated or the calibration method is incorrect, resulting in the accumulation of measurement errors.
Solution: Regularly calibrate the temperature controller using a standard temperature source.

4. Furnace structure and insulation performance issues
Poor sealing of furnace body
Reason: The furnace door, flange and other parts are not sealed tightly, resulting in heat loss and actual temperature lower than the measured value.
Detection method: Check the leakage point of the furnace body and repair the sealing components.
Aging of insulation materials
Reason: The performance of insulation materials has decreased, resulting in uneven temperature distribution inside the furnace and deviation between measured values and actual values.
Solution: Replace the aging insulation material.

5. Operation and process setting issues
Heating rate set too fast
Reason: The heating rate exceeds the equipment’s capacity, causing temperature control to lag and the measured value to be out of sync with the actual value.
Solution: Reasonably set the heating rate to avoid temperature overshoot.
The influence of samples on temperature
Reason: The heat absorption or release characteristics of the sample cause local temperature changes, which affect the measured values.
Solution: Optimize the placement of samples or use multi-point measurement of average temperature.

6. Environment and interference factors
electromagnetic interference
Reason: The strong electromagnetic field nearby interferes with the temperature sensor signal, resulting in measurement errors.
Solution: Block the sensor signal line and keep it away from interference sources.
Environmental temperature changes
Reason: The temperature fluctuation in the laboratory environment affects the heat dissipation of the furnace body, resulting in a deviation between the actual temperature and the measured value.
Solution: Control the laboratory environment temperature or insulate the furnace body.

7. Equipment aging and maintenance issues
Long term use of equipment
Reason: Aging of furnace body, heating elements and other components leads to a decrease in temperature control performance.
Solution: Regularly maintain the equipment and replace aging components.
Improper maintenance
Reason: Failure to clean, calibrate, and maintain the equipment according to regulations resulted in inaccurate temperature measurement.
Solution: Establish an equipment maintenance plan and strictly implement it.