The melting point apparatus is a commonly used instrument for determining the melting point of substances in fields such as chemistry, pharmaceuticals, and materials science. Its malfunction may involve multiple aspects including temperature control, optical systems, mechanical structures, or software operation. The following provides a detailed explanation from three dimensions: common fault phenomena, cause analysis, and solutions, to help users quickly locate problems and take effective measures.
I. Abnormal temperature control
1. Fault phenomenon
The actual temperature deviates significantly from the set value (for example, if the set temperature is 150℃, the actual temperature may be more than ±5℃ higher or lower).
The heating rate is unstable (sometimes fast and sometimes slow or fails to reach the preset rate).
Abnormal temperature display (jumping, black screen or fixed value remaining unchanged).
2. Possible causes
- Temperature sensor failure: The thermocouple or platinum resistance (RTD) probe is aged, loose or has poor contact.
- Heating element damage: The heating wire breaks or the heating block ages, resulting in a decrease in heating capacity.
- Temperature control circuit issues: PID control parameter imbalance, relay failure or unstable power supply voltage.
- Calibration offset: Long-term use without calibration leads to temperature indication deviation.
3. Solution
- Check the sensor:
- Confirm that the sensor is in good contact with the heating block, without any loosening or oxidation.
Calibrate with a standard thermometer (such as a high-precision mercury thermometer). If the deviation exceeds ±1℃, the sensor needs to be replaced.
- Test the heating system:
Disconnect the heating block from the main unit and directly power on to test whether the heating wire is heating up (please pay attention to safety).
If the heating wire is normal but the temperature rises slowly, it might be that the insulation layer inside the heating block is damaged. You need to contact the manufacturer for replacement.
Calibrate the temperature control program:
Enter the instrument Settings menu, select the "Calibration" function, and recalibrate the temperature as required by the manual (standard substances such as indium, benzoic acid, etc. must be used).
If the PID parameters are adjustable, try fine-tuning the proportional band (P), integral time (I), and differential time (D) parameters.
- Check the power supply and wiring
Ensure the power supply voltage is stable (some instruments require a voltage stabilizer), and check whether the line interfaces are oxidized or have poor contact.
Ii. Faults in the optical observation system
1. Fault phenomenon
The eyepiece or display screen cannot observe the melting process of the sample (the image is blurry, completely black or flickering).
The lighting is not working or has insufficient brightness, resulting in a dim view.
- Image distortion (such as blurred edges, inconsistent magnification).
2. Possible causes
- Light source failure: Halogen lamps, LED lamps or optical fibers have aged or burned out.
- Lens contamination: Oil stains, fingerprints or sample residues on the surface of the objective lens, eyepiece or reflector.
- CCD camera issues: Loose data cable, damaged image sensor or abnormal software driver.
- Hot stage obstruction: The position of the heating stage and the lens is offset, causing the light path to be blocked.
3. Solution
- Clean optical components:
After turning off the power, use lens cleaning paper dipped in anhydrous ethanol to gently wipe the surfaces of the objective lens, eyepiece and reflector.
Check the focusing distance between the hot stage and the lens and adjust it to the best observation position.
- Replace the light source:
If the lighting lamp burns out, replace it with a matching halogen lamp or LED lamp according to the instrument model (pay attention to the matching of power and voltage).
For optical fiber transmission type instruments, it is necessary to check whether the optical fiber interface has fallen off or broken.
- Check the camera and software:
Restart the instrument and enter the imaging software to test if the camera is recognized.
If the image is still abnormal, try updating the driver or replacing the camera.
- Adjust the optical path:
Make sure the heating table is coaxial with the light source and the lens to avoid tilting which may cause light scattering.
Iii. Mechanical Structure and Operational Faults
1. Fault phenomenon
The sample stage is stuck and cannot be raised, lowered or rotated.
The capillary tube is difficult to insert or not sealed tightly, resulting in sample leakage.
The touchscreen or buttons are malfunctioning, preventing the input of instructions.
2. Possible causes
- Wear of transmission components: Insufficient lubrication of lead screws, gears or guide rails after long-term use leads to jamming.
- Sample stage deformation: The heating and cooling cycle causes slight warping of the metal tabletop.
- Sealing aging: The rubber gasket of the capillary tube fixing device has hardened or been damaged.
- Misjudgment of operation: Failure to operate in accordance with the specifications (such as overloading the sample or forcibly rotating the sample stage).
3. Solution
- Lubrication and cleaning:
Disassemble the sample stage, clean the dust and oil stains on the lead screw and guide rail, and apply an appropriate amount of lubricating oil (such as silicone oil).
Check the meshing condition of the gears. If the teeth are worn, replace the parts.
- Calibration sample stage:
Check the flatness of the countertop with a level. Slight warping can be repaired by adjusting the screws on the base.
Replace the sealing gasket of the capillary tube and ensure that the sample tube is inserted vertically.
- Standard operation:
Avoid overloading the sample (such as overfilling causing capillary blockage), and fill it to the standard length (usually 2-3mm).
Operate the buttons or touch screen gently to avoid excessive force that may damage the circuit.
Iv. Software and Data Processing Issues
1. Fault phenomenon
Test data cannot be saved or reports cannot be exported.
The calculation result of the melting point deviates significantly from the manually observed value.
The instrument cannot be connected to a computer or a mobile phone APP.
2. Possible causes
- Insufficient storage space: Excessive data cache or damaged memory card.
- Incorrect algorithm parameter Settings: For instance, the melting point determination threshold (such as the maximum absorbance change rate) is set unreasonably.
- Communication protocol mismatch: USB interface, Bluetooth or Wi-Fi module failure.
- System file damage: Sudden power outage or software crash caused by virus.
3. Solution
- Clear storage space:
Delete useless historical data and check whether the memory card can be read and written normally.
Reset the instrument to factory Settings (note to back up important data).
- Calibration algorithm parameters:
Adjust the melting point determination threshold according to the sample characteristics (such as transparency and color depth), and manually enter the correction value if necessary.
- Check the communication connection
Replace the data cable or restart the router to ensure a stable Bluetooth /Wi-Fi signal.
Update the software version to the latest patch.
- Reinstall the system:
Contact the manufacturer to obtain the original firmware package and follow the instructions to restore the system to avoid data loss