How to distinguish the fault of the temperature co

2022-08-08
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How to distinguish the failure of temperature control instrument with switch output

Huaibei City has also increased efforts to attract investment and intelligence. First, the main fault discrimination method of the temperature control instrument output by the relay:

1. On the premise that the thermocouple or thermal resistance is in good condition and the instrument wiring is correct, the instrument does not rise after being powered on, and even the measured temperature drops (under the precondition that the set temperature is higher than the measured temperature)

1) when the main control output of the instrument is a relay, and the output and controlled circuit is an AC contactor (or intermediate relay); First, make sure that this output is controlled by contact

check whether the terminal wiring of the main control output is correct. Because the main control output of the instrument in our factory is a reaction, the closed end of the relay of the main control output of the instrument in our factory should be connected with one end of the wire package of the AC contactor (intermediate relay), and other wiring is correct. Although the green indicator light is on during the operation of the instrument, it does not heat up. (because the instrument is a reaction principle)

the main control output relay of the instrument always starts. On the premise of the correct connection with the wire package of the AC contactor (intermediate relay) as mentioned above, when the instrument is powered on and running, the green indicator light is on, but the temperature still does not rise

inspection method: put the multimeter at AC voltage and AC 250V, one meter bar on the multimeter is on the normally open terminal of the relay output of the instrument master control, and the other meter bar is on the neutral line of AC 220V power supply, and the multimeter shows whether there is AC 220V voltage

a) if there is no voltage value: it means that one end of the AC contactor (intermediate relay) package is not connected to the normally open terminal of the instrument main control output relay, but to the normally closed terminal of the instrument main control output relay (it means that there is no voltage input at both ends of the AC contactor or intermediate relay package)

inspection method: check whether there is useless wire connected to the intermediate terminal of the main control output relay of the instrument in the phase (fire) wire of AC 220V power supply. Or the internal open circuit of the wire used

the main control output relay of the instrument does not reverse after being powered on, indicating that the middle end and normally closed end of the main control relay of the instrument are locked

b) if there is about 220V AC voltage, it means that there is about 220V AC voltage at both ends of the AC contactor or intermediate relay package

inspection method: check whether the package voltage of AC contactor or intermediate relay is negative 220V. If the product requires the package voltage to be AC 380, the AC contactor (intermediate relay) will not work. It is required to replace the AC contact or intermediate relay with the package voltage of AC 220V

1) it meets the above requirements and cannot work normally. Put a multimeter on the resistance when there is no electricity × On the 10th gear, press the two meter bars of the multimeter on both ends of the wire package of the intermediate relay of the AC contactor. If the resistance value is large, it indicates that the coil in the wire package is disconnected or damaged, and the AC contactor or intermediate relay should be replaced. If there is a resistance value, it means that there is no iron core in the wire package, which cannot generate electromagnetic suction and cannot work. The AC contactor or intermediate relay should be replaced

2. During the operation of the instrument, the measured temperature has been higher than the set temperature, and the green indicator light of the instrument has been off, but the measured temperature has been rising

inspection method:

1) when the main control output of the table is the relay contact output, and the controlled circuit is AC contactor or intermediate relay

(1) when the instrument is not powered on, use a multimeter to measure the resistance × 1 Ω gear to detect, the signal meter main control relay Middle Temple and the constant start resistance value to distinguish

① if there is resistance, or even the resistance value is very small, it indicates that the middle end of the relay output by the main control of the instrument and the normal start are locked due to long-term work. The relay output by the main control of the instrument should be replaced, and the instrument can only be replaced on site

② if the resistance value is large, it indicates that the relay of the main control output of the instrument is in good condition, and there may be problems with the AC contactor or intermediate relay in the controlled circuit. Inspection method:

use multimeter resistance × 1 Ω gear to detect the resistance value of the constant start of the AC contactor or intermediate relay. If there is resistance value, even the resistance value is very small. It indicates that the AC contactor or intermediate relay often starts to bite due to long-term work. Only the AC contactor or intermediate relay can be replaced. On the contrary, if the resistance value is large, it indicates that the AC contactor or intermediate relay is in good condition

(2) when the instrument is powered on, it is believed that the instrument is in operation. When the measured temperature is higher than the set temperature, the green indicator light of the instrument is off and greater than 10 ℃, put the multimeter on the AC voltage 250V gear, and use a multimeter stick at the beginning of the main control relay of the instrument; Another meter stick is on the neutral line of AC 220V power supply, and the multimeter shows whether there is voltage value. ① If the voltage value is still about 220V AC, it means that the main control relay of the instrument has been working for a long time and is bitten, and the instrument should be replaced. ② If there is no voltage value, it indicates that the main control relay of the instrument is in good condition. Using the above inspection method, use a multimeter to check whether there is a voltage value with one meter bar at the outgoing line of the AC contactor or intermediate relay at the normal beginning and the other meter bar at the neutral line of the AC 220V power supply. If there is a voltage value of about 220V AC, it means that the AC contact or intermediate relay often starts to work for a long time and bites, and it should be replaced. If there is no voltage value, the normal start of AC contactor and intermediate relay is intact

II. Main fault discrimination method of SSR (level output) temperature control instrument:

1. On the premise that the thermocouple or thermal resistance is in good condition and the instrument wiring is correct, the instrument will not rise after being powered on, and even the measured temperature will fall down (under the precondition that the set temperature is higher than the measured temperature)

when the main control output of the instrument is SSR (level) output and the controlled circuit is externally connected with solid-state relay. First of all, you should find out the main control output of this instrument. When the green indicator light on the instrument is on, there is 12V level on the main control output terminal. When the green indicator light is dark, there is no level or ov

inspection method

1) under the condition of no power supply

check whether the wiring between the instrument main control output and the solid-state relay is correct. The instrument main control output SSR has (+) and (-) connected with the two small screws on the solid-state relay or the (+) and (-) of the signal control end of the solid-state relay must be correct. At the same time, connect the connected wires with Multimeter resistance × 1 Ω gear, measure whether the connection is open

2) under the condition of electricity:

use the DC voltage 20V gear of the multimeter, press the two rods of the multimeter on the two terminals of the main control output of the instrument (but make sure the positive and negative). When the green indicator light of the instrument is on, whether there is 12V DC voltage

a) if there is no 12V measured by the multimeter, there is a problem with the main control output of the instrument. Check whether the model of the instrument is correct, and replace the instrument

b) if there is 12V measured by the multimeter, it indicates that there is a problem with the solid-state relay, and the solid-state relay should be replaced. When it is not powered on, first remove the connecting wire of the phase (fire) wire of the AC 220V power supply at the big screw of the solid-state relay, then power on, and use the multimeter resistance × In gear 1, press the two rods of the multimeter on the two big screws of the solid-state relay. When the green indicator light of the instrument is on, the resistance value displayed by the multimeter is very large, which also indicates that the solid-state relay has problems and should be replaced. On the contrary, when the resistance value displayed by the multimeter is close to 0, it indicates that the solid-state relay is in good condition

2. During the operation of the instrument, the measured temperature has been higher than the set temperature, and the green indicator light of the instrument has been extinguished, but the measured temperature has been rising. The main control output of the instrument is SSR (adding active additives to the level and adopting polypropylene with wide molecular weight distribution also have a certain effect on the improvement of tiger skin defects), and the controlled circuit is a solid-state relay

inspection method:

(1) when the instrument is not powered on, turn the multimeter resistance × On the 1K Ω gear, use the two meter rods of the multimeter to put them on the two big screws of the solid-state relay (but remove the connection between the big screw and the layman)

① if the resistance value ∞ displayed on the multimeter is large, it indicates that the solid-state relay is intact in cold state

② if the multimeter shows resistance or the resistance value is very small, it indicates that the solid-state relay is damaged and needs to be replaced

(2) when the instrument is powered on, during the operation of the instrument, when the measured temperature is higher than the set temperature and greater than 10 ℃, the green indicator light of the instrument is off, put the multimeter on the DC voltage 20V gear, and use the two meter rods on the multimeter at both ends of the main control output of the instrument, but the positive and negative should be clear, and whether there is a voltage value displayed on the multimeter

① if the multimeter shows a DC 12V voltage value, it indicates that there is a problem with the instrument and the instrument should be replaced

② if there is no voltage value displayed on the multimeter, it indicates that the instrument is normal and intact. Then check the solid-state relay. The method is to remove the wiring between the solid-state relay big screw and the outside world before powering on. After power on, put the multimeter on the resistance × On the 1K Ω gear, use the two meter rods of the multimeter to put them on the two big screws of the solid-state relay. If the multimeter shows a resistance value and the resistance value is very small, it means that the solid-state relay is short circuited when it is hot, and the solid-state relay should be replaced. On the contrary, when the resistance value ∞ is large, it indicates that the solid-state relay is intact in cold state

III. main fault discrimination method of temperature control instrument with pulse output:

1. On the premise that the thermocouple or thermal resistance is in good condition and the instrument wiring is correct, the instrument does not rise after being powered on, and even the measured temperature drops downward (under the precondition that the set temperature is higher than the measured temperature)

when the main control output of the instrument is pulse output, bidirectional thyristor is used in the circuit. First of all, what is the main control output of the instrument? The main control output of the instrument is a pulse signal

inspection method:

when the main control output end of the instrument is not connected to the outside world, put the multimeter on the DC voltage 0.5V gear, press the two meter rods of the multimeter on the main control output terminal of the instrument (make sure the positive and negative) and power on, the green indicator light of the instrument is on (the set temperature of the instrument is higher than the measured temperature), and the multimeter shows that if there is a little voltage, the instrument has pulse output, and the instrument output is normal When the contemporary number is g (or unsigned), the main control output is determined by whether the small thyristor in the instrument is conductive. All wires connected to the outside world on the output terminal of the instrument are removed, and the multimeter is placed on the resistance × 1 Ω gear ensures the safety of experimental personnel and equipment. When powered on, the green indicator light of the instrument is on (it is believed that the set temperature of the instrument is higher than the measured temperature), the multimeter displays a small resistance value, and the main control output of the instrument is normal. On the contrary, the no voltage of code m and the resistance value of code g or no such symbol are very large, indicating that there is a problem with the instrument, and the instrument should be replaced

according to the above, if there is no problem with the instrument, check the following conditions

1) whether the wiring between the main control output of the instrument and the bidirectional thyristor is correct. The wiring must be carried out according to the wiring diagram marked on the wiring terminal in the product instruction manual, otherwise it cannot be carried out normally

2) check the quality of high-power bidirectional thyristor in the circuit

a) under the condition of no power, gently pull the control pole of bidirectional thyristor to see whether it is reliable. If it is loose or falls off, it means that the bidirectional thyristor is broken and needs to be replaced

b) under the condition of no power supply, use a multimeter to measure the resistance × 1 Ω gear, a meter bar on the multimeter is pressed on the control pole of the bidirectional thyristor, and a meter bar is on the cathode. If the resistance value displayed on the multimeter is large or there is no resistance value, it means that the bidirectional thyristor is broken and needs to be replaced. Under normal conditions, the resistance value is between ≥ 20 Ω and ≤ 80 Ω

c) when the instrument is not powered on, first remove the connection between the high-power bidirectional thyristor anode and the cathode in the circuit and the outside world. Put the multimeter on the resistance × On 1K Ω gear, use a multimeter on a meter

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