Abnormal temperature of lab graphite furnace
10-23-2025 Author: KJ technology
The abnormal temperature of the laboratory graphite vacuum furnace may be caused by incorrect temperature controller parameters, breakdown of solid-state relays, poor or damaged thermocouple contact, heating element failure, abnormal cooling system, unreasonable material layout in the furnace, or temperature control system failure. It is necessary to investigate and handle each phenomenon one by one. The following are specific reasons and solutions:
1. High temperature alarm
Temperature controller parameter error:
Check if the temperature controller parameters in the workspace are normal, and refer to other temperature controllers in normal use to calibrate all parameters.
Solid state relay breakdown:
Check whether the output terminal of the solid-state relay in the corresponding working area is broken down according to the circuit diagram.
Specific method: After a power outage, use a multimeter to measure the resistance between the two output points of the solid-state relay. Normally, the resistance should be several megohms or more. If it is broken down, there will be almost no resistance, and a new one of the same model should be used.
Poor or damaged thermocouple contact:
When powered on, gently shake the thermocouple probe in the corresponding working area by hand and observe whether the temperature controller displays a large jumping amplitude.
If so, it indicates poor contact of the thermocouple probe and needs to be replaced with a new one.
The thermocouple can also be swapped with the thermocouple on a normal thermostat and connected to the thermostat to observe the temperature display to verify if the thermocouple is damaged.
Heating element malfunction:
Check whether the heating element (such as graphite heating rod or heating wire) is damaged or aged, causing overheating.
If any problems are found with the heating element, it should be replaced or repaired in a timely manner.
Abnormal cooling system:
Check if the cooling system is operating normally, such as water flow rate, water temperature, etc.
If there is a malfunction in the cooling system, it should be repaired in a timely manner to ensure the cooling effect.
2. The displayed temperature is too low to reach the set value
Temperature controller parameter error or no output signal:
Check if the parameters of the temperature controller in the work area are normal and if there is an output signal.
Thermocouple damage:
Check if the thermocouple in the corresponding work area is damaged.
The thermocouple can be swapped with the thermocouple on a normal thermostat and connected to the thermostat to observe the temperature display.
If the thermocouple is indeed damaged, it must be replaced.
Heating element not powered on:
After powering on, start heating and directly test the wires connected to the heating tube in the corresponding working area using a test pen according to the circuit diagram (the white high-temperature wire on the solid-state output terminal is the one) to see if there is electricity.
If there is electricity arriving, it is necessary to use a clamp meter to measure whether the current is different from other working areas. Under normal circumstances, the difference is not significant.
If there is no electricity arriving, the circuit must be checked one by one according to the circuit diagram to see where the electricity is cut off and whether any components are burned out.
3. Unstable temperature or uneven heating speed
Unreasonable layout of heating elements:
Adjust the position and layout of the heating element to ensure even heating.
Decreased insulation performance of furnace body:
Check the insulation performance of the furnace body to ensure that there is no heat loss.
Temperature control system malfunction:
Check and adjust the temperature control system to ensure proper operation.
If there is a malfunction in the temperature control system, relevant components should be repaired or replaced in a timely manner.
