Fault identification method of temperature control instrument

How to distinguish the fault of temperature control instrument

First, the main fault identification method of relay output temperature instrument:

1. Under the premise that the thermocouple or thermal resistance is in good condition and the instrument is connected correctly, the instrument does not heat up after being energized, and even the phenomenon of measuring temperature falling (the set temperature is higher than the prerequisite for measuring temperature).

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

Check whether the terminal connection of the main control output is correct. For the instrument whose main control output is reactive, the relay closed end of the main control output should be connected to the wire package end of the AC contactor (intermediate relay), and the other wiring is correct, although the instrument is running, the green indicator is on, but it does not heat up. (Since the meter is a reaction principle). The output relay of the main control of the instrument usually starts. Under the premise that the cable package of the AC contactor (intermediate relay) is connected correctly, the green indicator is on when the instrument is powered on and still does not heat up. Check method: Put the multimeter in the AC voltage and AC 250V gear. Place one meter rod on the normally open terminal of the relay output by the main control of the meter, and place the other meter rod on the middle line of the AC 220V power supply. The multimeter displays whether the AC 220V voltage is present.

A) If there is no voltage value: it indicates that one end of the AC contactor (intermediate relay) wire package is not connected to the normal start of the instrument main control output relay, but is connected to the normally closed terminal of the instrument main control output relay, (indicating that there is no voltage input at both ends of the AC contactor or intermediate relay wire package). Check the method, check the AC 220V power supply phase (fire) line has unnecessary wires connected to the middle terminal of the instrument master output relay. Or caused by the internal opening of the wire used. The output relay of the instrument master control does not reverse after being powered on, indicating that the middle end of the instrument master control relay and the normally closed end are bitten.

B) If there is about 220V AC voltage, it means that both ends of the AC contactor or intermediate relay wire package are about 220V AC voltage plus. Check method: Check the packet voltage of the AC contactor or intermediate relay is negative 220V. The AC contactor (intermediate relay) will not work if the product requires a packet voltage of AC 380. It is required to replace the AC contact or intermediate relay with the packet voltage of AC 220V.

2) Meet the above requirements, can not work normally. In the case of no power, put the multimeter on the resistance ×10, and press the two meter rods on the two 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, the AC contactor or the intermediate relay should be replaced. If there is a resistance value, it indicates 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 measuring temperature has been higher than the set temperature, and the green indicator light of the instrument has been extinguished, but the measuring temperature has been rising.

Inspection method:

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

(1) When the instrument is not powered on, the multimeter resistance × 1ω is used to detect, and the value of the middle temple and the normal opening resistance of the main control relay of the signal meter is judged.

① If there is resistance, or even a small resistance value, it indicates that the middle end of the relay and the normal beginning of the instrument main control output are bitten by long-term work, and the relay of the instrument main control output should be replaced, and the instrument can only be replaced on the spot.

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

Use the multimeter resistance ×1Ω to detect the resistance value of the normal beginning of the AC contactor or intermediate relay. If there is a resistance value, even the resistance value is very small. Ac contactors or intermediate relays often start to die due to long-term work. Only replace the AC contactor or intermediate relay. Conversely the resistance value is very large, said

Clear AC contactor or intermediate relay in good condition.

(2) When the instrument is powered on, the instrument is in operation, when the measuring temperature is higher than the set temperature, the green indicator light of the instrument is off, and is greater than 10 ° C, put the multimeter on the AC voltage 250V, and use a meter bar in the normal start of the main control relay of the instrument; Another meter bar shows whether there is a voltage value in the midline multimeter of the AC 220V power supply.

① If the AC voltage is still about 220V, it indicates that the main control relay of the instrument is bitten by long-term work, 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 check method, use a multimeter to check whether there is a voltage value at the outlet of the AC contactor or intermediate relay, and another meter to check whether there is a voltage value at the middle line of the AC 220V power supply. If there is an AC 220V voltage value, it indicates that the AC contact or intermediate relay often starts to work for a long time and dies, and should be replaced. If there is no voltage value, it indicates that the normal opening of the AC contactor and the intermediate relay is intact.

Second, SSR(level output) temperature control instrument main fault identification method:

1, the thermocouple or thermal resistance is intact and the instrument wiring is correct under the premise that the instrument does not heat up after power, and even the phenomenon of measuring temperature falling (the set temperature is higher than the measurement temperature prerequisite) the main control output of the instrument is SSR(level) output and the controlled circuit is an external solid-state relay. It should first be understood that when the main control output of the instrument is on, the green indicator is on, the main control output terminal has a 12V level, and when the green indicator is dark, no level or OV.

Inspection method:

1) In the case of no power, check whether the connection between the instrument master control output and the solid-state relay is correct, and the instrument master control output SSR has (+) and (-) the two small screws on the solid-state relay, or the solid-state relay signal control end (+) and (-) must be connected correctly. At the same time, use the multimeter resistance x 1Ω to measure whether the connection is open.

2) In the case of power, use the multimeter DC voltage 20V, press the two meter rods on the two terminals of the main control output of the instrument (but make sure that the positive and negative), and whether there is 12V DC voltage when the green indicator of the instrument is on.

A) If no 12V is measured by the multimeter, the main control output of the meter is faulty. Check whether the model of the instrument is correct and replace the instrument.

B) If the multimeter measures 12V, it indicates that there is a problem with the solid-state relay. To replace the solid-state relay, you can also remove the cable connecting to the AC 220V power phase (fire) line at the big screw of the solid-state relay when there is no power supply, and then power on, press the two rods of the multimeter on the two big screws of the solid-state relay with the multimeter resistance ×1. When the green indicator of the instrument is on, the resistance value displayed by the multimeter is very large, which also indicates that the solid-state relay has a problem 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 measuring temperature has been higher than the set temperature, and the green indicator light of the instrument has been extinguished, but the measuring temperature has been rising. The main control output of the instrument is SSR(level), and the controlled circuit is a solid-state relay.

Inspection method:

(1) When the meter is not powered on, put the multimeter resistance ×1KΩ on the gear, and use the two meter rods of the multimeter on the two large 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, the solid-state relay is in good condition when it is cold.

② If the multimeter shows resistance or resistance value is very small, it indicates that the solid-state relay is damaged and should be replaced.

(2) When the meter is powered on, when the meter is running, when the measurement temperature is higher than the set temperature and is greater than 10 ° C, the green indicator light of the meter is off, the multimeter is placed on the DC voltage 20V file, and the two meter bars on the multimeter are used at both ends of the main control output of the meter, but the positive and negative values should be made clear whether there is a voltage value displayed on the multimeter.

① If the DC 12V voltage is displayed on the multimeter, it indicates that the meter is faulty and should be replaced.

② If no voltage is displayed on the multimeter, the meter is in good condition. Then check the solid state relays. The method is to remove the connection between the big screw of the solid-state relay and the outside world before the power is turned on. After power, put the multimeter on the resistance ×1KΩ, and use the two meter rods of the multimeter on the two large screws of the solid-state relay. If the multimeter shows a resistance value and the resistance value is very small, it indicates that the solid-state relay is short circuit 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 in good condition when cold.