Troubleshooting of super constant temperature oil bath and water bath

The following is the constant temperature oil bath in the heating process prone to failure: first, temperature setting, temperature measurement is normal but not heated First, judge from the screen display, first turn on the power supply, and adjust the set temperature to more than 20% of the design temperature Then observe whether the heating indicator is on If it is on, it means that the heating tube is broken or the relay contact cannot be connected because the contact is ablated during long-term use, so it cannot be heated It needs to be replaced It can also be checked by multimeter The check method is to turn off the power supply and use the multimeter resistance gear (10 Ohm) is the resistance small? The resistance of the heating tube of the oil bath is generally less than 100 ohm If the resistance is large, it must be that the heating tube is broken, the resistance is normal, and the relay is mostly damaged II The temperature setting and temperature measurement are normal, but the temperature will continue to be heated when it reaches the set temperature (for the oil bath pot used for the first time, there will be overtemperature due to the use of microcomputer PID control mode, but the overtemperature generally will not exceed 10 ℃, the effect is better after self-tuning for the first use) Observe whether the heating indicator goes out after reaching the set temperature If it goes out, it means that the temperature controller is normal Just replace the relay If the heating indicator is always on, the temperature controller is broken and needs to be replaced 3 After using for a period of time, it is found that the temperature cannot be increased, mostly because the resistance of the heating pipe becomes larger or the connecting wire with the heating pipe is rusted, resulting in the contact resistance becoming larger The former needs to replace the heating pipe, and the latter cuts off the wire head at the connection, and at the same time, the rusted part of the heating pipe joint is cleaned, and the connection can be reconnected Two judgment methods can be determined by visual inspection IV after setting the temperature, the temperature measurement shows a decrease, but the actual temperature is in the heating state (k sensor is applicable, PT100 sensor will not have this phenomenon) This phenomenon often occurs in the replacement of new sensor, just exchange the positive and negative poles of the sensor V if the display shows 000 or 999, it means the sensor is open or short circuited Replace it Vi there is no power supply for the whole machine Check whether the power socket has power, whether the fuse is in good condition, and whether the power switch has fault Most of the fault is that the power switch is damaged VII The power indicator is on, but the temperature controller has no screen display Check whether the output of lm7805 on the temperature controller is normal Generally, this fault is mainly caused by the transformer on the temperature controller is broken or the lm7805 has faulty welding during use (lm7805 is a heating element) 8、 Due to the circulation function of super constant temperature oil bath, if the circulation pump does not turn, this phenomenon is mostly capacitance without capacity, replacement is enough Judgment method: turn on the power switch, turn on the power supply of the circulating pump, and turn the motor shaft by hand If it turns, it means that the capacitance is broken If it doesn't turn, the motor is faulty.