Sigma centrifuge maintenance fault analysis and solution
2024-06-08 19:06:17
Sigma centrifuge failure phenomenon <br> Since the centrifuge power supply is turned on, the initialization process is first performed to detect the core circuit. If there is a problem in the initialization process, it is in a shutdown state and enters an infinite loop. According to the failure phenomenon, the machine can be initially judged to be absent. The main reasons for the initialization process, resulting in no initialization process are:
(1) The microprocessor upd7810 on the control board is not reset;
(2) There is no clock signal;
(3) The program in the ROM is damaged;
(4) Microprocessor upd7810 damage repair method In the maintenance process, the principle of easy and difficult to be used should be taken first, first check the reset condition of the micro process. The low-level signal is instantaneously sent to the 28-pin reset end of the microprocessor upd7810. The machine enters the normal working state, and the display panel also works normally. This indicates that the fault occurs in the reset circuit. After the machine works for a period of time, the performance of the component changes, resulting in a reset pulse that does not meet the requirements (a normal reset pulse is about ten ns). After re-adjusting the capacitor C3 in the reset circuit, the machine works normally. If the Z11 and TL7705 integrated blocks are damaged, if they are not available, they can be replaced by an integral circuit r=RC>12ns.
Symptoms of sigma centrifuges <br> After starting up, when the speed of the rotor reaches 830r/min when the rotor is rising speed, the rotor lamp flashes and the rotor stops rising and enters the free decay state.
The main cause of such failure phenomena in fault analysis is the rotor speed detection circuit. Such as RPG (rotor pulse generator) sensor is bad; transistor aging, deterioration of characteristics, current amplification factor or resistance variable is the cause of such failure.
The inspection method checks the RPGA point pulse signal by about 3Vp-p, and the pulse width changes with the increase of the rotational speed. This indicates that the RPG sensor works normally, the collector Q4 and Z32 input terminals are both 2.8Vp-p pulse signals, and the output of Z32 The terminal is at +5V DC level (normally, it should be 5Vp-p pulse signal). Since the threshold voltage of Z32 is about 3V, the input 2.8Vp-p pulse cannot turn the inverter on. At this time, the detection state of the micro processing is wrong, and the rotor lamp is shining. Check Q4 collector current is lower than the normal value, in the case of Q4 aging is not serious, the output voltage of Q4 can be raised to high, that is, the collector resistance R31 is reduced, the collector current is increased, and Q4 is reached. The saturation is turned on, and the collector output is about 5Vp-p pulse signal and the machine resumes normal operation.
Sigma centrifuge failure phenomenon three <br> At room temperature l6 ° C or so, the boot temperature shows a 10 ° C, the temperature can be set normally, but the instrument can not work properly.
The reasons for the fault detection caused by the fault analysis are: (1) the thermal sensor is bad; (2) the temperature detecting circuit is faulty.
The inspection method checks that the thermal sensor is normal, the output of the op amp upc451 is 0V, and the output of the VR7 op amp (Fig. 4) remains unchanged, so it is determined that the operational amplifier is bad. Because the same type of four op amp upc451 is not available in the market, the LM324 with the same component foot arrangement is directly replaced. The measured temperature is slightly different from the actual temperature after the replacement, because the performance of the two integrated circuits is incomplete. Consistently caused. Therefore, it is necessary to carry out the calibration of the temperature measurement. After the instrument has been repaired, the temperature measurement circuit must be adjusted to calibrate the measured temperature.
Sigma centrifuge failure phenomenon four:
After pressing the start button, the motor runs for 5 seconds to indicate an imbalance error and cannot continue working.
Inspection method: 1. Check whether the centrifuge tube is placed symmetrically. If the asymmetry is removed, the symmetry can be solved.
2. Remove the rotor and clean the centrifuge tube with alcohol. The dirty inside will cause an imbalance error.
3. Check if the balance sensor is aging or misplaced, reinstall or replace the problem.
Reasons for corrosion of sigma centrifuge rotor and repair Why is the centrifuge rotor corroded during the process of using the centrifuge? Let's take a look at the specific reasons for the corrosion of the centrifuge rotor.
The corrosion of the rotor is usually caused by two aspects: chemical corrosion and stress corrosion:
1. Chemical corrosion on the surface of the rotor Under normal conditions, the surface of the aluminum rotor has an anodized oxidized protective film, but it is very brittle and can be scratched by sharp objects when careless. Acids, alkalis and detergents can also erode it. Some high-concentration salts also have an adverse effect on the aluminum rotor. It is stable only in mediums that are close to neutral (pH = 6.5 to 7.5).
2. Stress corrosion The rotor life is determined by mechanical fatigue strength test under non-corrosive conditions. However, in actual work, due to chemical corrosion, corrosion spots will be locally generated on the rotor surface, which will reduce the mechanical properties of the material and lead to stress concentration. Stress corrosion occurs. In the presence of stress corrosion, even if the stress is lower than the design limit of the rotor and the life index is not reached, the cracking phenomenon of the rotor frequently occurs. Stress corrosion is the main cause of scrapping aluminum alloy rotors. After the rotor has been used for a certain period of time, it must be checked regularly to avoid corrosion.
(1) The microprocessor upd7810 on the control board is not reset;
(2) There is no clock signal;
(3) The program in the ROM is damaged;
(4) Microprocessor upd7810 damage repair method In the maintenance process, the principle of easy and difficult to be used should be taken first, first check the reset condition of the micro process. The low-level signal is instantaneously sent to the 28-pin reset end of the microprocessor upd7810. The machine enters the normal working state, and the display panel also works normally. This indicates that the fault occurs in the reset circuit. After the machine works for a period of time, the performance of the component changes, resulting in a reset pulse that does not meet the requirements (a normal reset pulse is about ten ns). After re-adjusting the capacitor C3 in the reset circuit, the machine works normally. If the Z11 and TL7705 integrated blocks are damaged, if they are not available, they can be replaced by an integral circuit r=RC>12ns.
Symptoms of sigma centrifuges <br> After starting up, when the speed of the rotor reaches 830r/min when the rotor is rising speed, the rotor lamp flashes and the rotor stops rising and enters the free decay state.
The main cause of such failure phenomena in fault analysis is the rotor speed detection circuit. Such as RPG (rotor pulse generator) sensor is bad; transistor aging, deterioration of characteristics, current amplification factor or resistance variable is the cause of such failure.
The inspection method checks the RPGA point pulse signal by about 3Vp-p, and the pulse width changes with the increase of the rotational speed. This indicates that the RPG sensor works normally, the collector Q4 and Z32 input terminals are both 2.8Vp-p pulse signals, and the output of Z32 The terminal is at +5V DC level (normally, it should be 5Vp-p pulse signal). Since the threshold voltage of Z32 is about 3V, the input 2.8Vp-p pulse cannot turn the inverter on. At this time, the detection state of the micro processing is wrong, and the rotor lamp is shining. Check Q4 collector current is lower than the normal value, in the case of Q4 aging is not serious, the output voltage of Q4 can be raised to high, that is, the collector resistance R31 is reduced, the collector current is increased, and Q4 is reached. The saturation is turned on, and the collector output is about 5Vp-p pulse signal and the machine resumes normal operation.
Sigma centrifuge failure phenomenon three <br> At room temperature l6 ° C or so, the boot temperature shows a 10 ° C, the temperature can be set normally, but the instrument can not work properly.
The reasons for the fault detection caused by the fault analysis are: (1) the thermal sensor is bad; (2) the temperature detecting circuit is faulty.
The inspection method checks that the thermal sensor is normal, the output of the op amp upc451 is 0V, and the output of the VR7 op amp (Fig. 4) remains unchanged, so it is determined that the operational amplifier is bad. Because the same type of four op amp upc451 is not available in the market, the LM324 with the same component foot arrangement is directly replaced. The measured temperature is slightly different from the actual temperature after the replacement, because the performance of the two integrated circuits is incomplete. Consistently caused. Therefore, it is necessary to carry out the calibration of the temperature measurement. After the instrument has been repaired, the temperature measurement circuit must be adjusted to calibrate the measured temperature.
Sigma centrifuge failure phenomenon four:
After pressing the start button, the motor runs for 5 seconds to indicate an imbalance error and cannot continue working.
Inspection method: 1. Check whether the centrifuge tube is placed symmetrically. If the asymmetry is removed, the symmetry can be solved.
2. Remove the rotor and clean the centrifuge tube with alcohol. The dirty inside will cause an imbalance error.
3. Check if the balance sensor is aging or misplaced, reinstall or replace the problem.
Reasons for corrosion of sigma centrifuge rotor and repair Why is the centrifuge rotor corroded during the process of using the centrifuge? Let's take a look at the specific reasons for the corrosion of the centrifuge rotor.
The corrosion of the rotor is usually caused by two aspects: chemical corrosion and stress corrosion:
1. Chemical corrosion on the surface of the rotor Under normal conditions, the surface of the aluminum rotor has an anodized oxidized protective film, but it is very brittle and can be scratched by sharp objects when careless. Acids, alkalis and detergents can also erode it. Some high-concentration salts also have an adverse effect on the aluminum rotor. It is stable only in mediums that are close to neutral (pH = 6.5 to 7.5).
2. Stress corrosion The rotor life is determined by mechanical fatigue strength test under non-corrosive conditions. However, in actual work, due to chemical corrosion, corrosion spots will be locally generated on the rotor surface, which will reduce the mechanical properties of the material and lead to stress concentration. Stress corrosion occurs. In the presence of stress corrosion, even if the stress is lower than the design limit of the rotor and the life index is not reached, the cracking phenomenon of the rotor frequently occurs. Stress corrosion is the main cause of scrapping aluminum alloy rotors. After the rotor has been used for a certain period of time, it must be checked regularly to avoid corrosion.
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