How to determine the temperature control instrument output failure

First, the relay output temperature instrument main fault method

1. If the condition of the thermocouple or thermal resistor is in good condition and the instrument wiring is correct, the instrument will not heat up after being energized, or even measure the phenomenon of temperature drop (set temperature is higher than the measurement temperature precondition).

1) The main control output of the instrument is a relay. When the output is controlled by an AC contactor (or intermediate relay), the output is first known as contact control.

Check if the terminal wiring of the master output is correct. Because the main control output of our factory is counterproductive, the relay closed end of the main control output of our factory should be connected with the end of the line contact of the AC contactor (intermediate relay). The other wiring is correct. Although the indicator is running, the green indicator light is on, but Do not warm up. (Because the instrument is a reaction principle).

Instrument control output relay normally open end, according to the above and AC contactor (intermediate relay) wire package connection under the premise of the instrument power operation, the green indicator light, still not warming.

Inspection method: put the multimeter on the AC voltage, AC 250V file, a meter stick on the multimeter is on the normally open terminal of the relay output of the meter main control, another table stick is placed on the midline of the AC 220V power supply, 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) wire package is not connected to the normally open terminal of the meter main control output relay, but is connected to the normally closed terminal of the relay of the main control output of the instrument. There is no voltage input at both ends of AC contactor or intermediate relay wire package).

Check the method and check if the 220V power phase (fire) wire is connected to the middle terminal of the main control output relay of the instrument. Or the wire used inside is caused by an open circuit.

The main control output relay of the instrument did not reverse after being energized, indicating that the middle and the normally closed ends of the main control relay of the instrument were killed.

B) If there is about 220V AC voltage, it means that there are about 220V AC voltage at both ends of the AC contactor or intermediate relay line pack.

Inspection method: Check whether the voltage of the AC contactor or intermediate relay is 220V. If the product requires the line voltage to be AC ​​380 AC contactor (intermediate relay), it will not work. It is required to replace the AC contact or intermediate relay with AC 220V.

1) In compliance with the above requirements, it still cannot work normally. Under the non-energized condition, use the multimeter to put on the resistance×10 gears, and press the two meter sticks of the multimeter on both ends of the wire relay of the relay in the middle of the AC contactor. If the resistance value is very large, it means that the coil in the wire pack is broken. Open or damaged, should exchange AC contactors or intermediate relays. If there is a resistance value, it means that there is no iron core in the wire package, and no electromagnetic attraction can be generated and it cannot work. Exchange AC contactors or relays should be replaced.

2. In the operation of the instrument, the measured temperature is higher than the set temperature, and the green indicator of the instrument is extinguished, but the measurement temperature is still rising.

Inspection Method:

1) The master output of the watch is the relay contact output, while the controlled circuit is the AC contactor or intermediate relay.

(1) When the instrument is not powered, use a multimeter resistance × 1Ω file to detect, and the resistance value of the middle temple and the normally open resistance of the master control relay is determined.

1 If there is resistance or even a small value of the resistance, it means that the middle and end of the relay of the main control output of the instrument is dead due to long-term work. The relay of the main control output of the instrument should be exchanged, and the instrument can only be replaced at the scene.

2 If the resistance value is large, it means that the relay of the main control output of the instrument is in good condition, and the AC contactor or intermediate relay in the controlled circuit may have problems. Inspection Method:

Use multimeter resistance × 1Ω to detect the resistance value of the normally open contact of the AC contactor or intermediate relay. If there is a resistance value, even the resistance value is small. Description The AC contactors or intermediate relays often start to die due to long-term work. Only replace AC contactors or intermediate relays. On the other hand, the resistance value is very large, indicating that the AC contactor or intermediate relay is intact.

(2) When the instrument is powered on, the letter instrument is in operation. When the measured temperature is higher than the set temperature, the green indicator of the instrument is off, and when the temperature is greater than 10°C, put the multimeter on the AC voltage of 250V, using a multimeter. The meter stick is at the normally open end of the instrument's master control relay; the other meter stick's midline multimeter at the AC 220V supply shows the voltage value. 1 If the AC voltage of 220V is still about, it means that the master control relay of the instrument has been killed for a long time and the instrument should be replaced. 2 If there is no voltage value, the instrument master control relay is in good condition. Then use the above inspection method, use a multimeter to wrap the outlet of the AC contactor or intermediate relay at the outlet of the normally open end of the AC contactor, and another table stick to the midline of the AC 220V power supply. Is there any voltage value? If there is an AC voltage of about 220V, it means that the AC contact or the intermediate relay always starts to work and it is killed. It should be replaced. If there is no voltage value, the normally open end of the AC contactor and intermediate relay is intact.

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

1. If the condition of the thermocouple or thermal resistance is in good condition and the instrument wiring is correct, the instrument does not heat up after power on, and even measures the phenomenon of temperature drop (preset temperature is higher than the measurement temperature)

When the main control output of the meter is an SSR (level) output and the circuit to be controlled is an external solid state relay. Should first find out the main control output of this instrument, the green indicator light on the indicator is on, the main control output terminal has 12V level, and when the green indicator light is dark, there is no level or OV.

Inspection Method

1) In the absence of power

Check whether the wiring between the main control output of the instrument and the solid state relay is correct. The main control output SSR of the instrument has (+) and (-) with the two small screws on the solid state relay or the (+) and (-) signal control terminal of the solid state relay. ) The connection must be correct. At the same time, connect the line with a multimeter resistance × 1Ω, and measure if the connection is open.

2) In the case of electricity:

With the multimeter's DC voltage 20V, press the multimeter's two meter sticks on the two terminals of the meter's main control output (but figure out the positive and negative). When the indicator's green indicator light is on, is there a 12V DC voltage?

A) If the multimeter measures no 12V, there is a problem with the meter's master output. Check whether the model of the instrument is correct and replace the instrument.

B) If the multimeter has 12V measurement, it means there is a problem with the solid state relay. To replace the solid state relay, you can also remove the connection of the alternating current 220V power phase (fire) wire at the large screw of the solid state relay when it is not powered. Then power on, use a multimeter resistance × 1 file, the two sticks of the multimeter are pressed on the two large 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. It also shows that the solid state relay has problems and should be replaced. Conversely, when the resistance value of the multimeter shows close to 0, the solid state relay is in good condition.

2. In the operation of the instrument, the measured temperature is higher than the set temperature, and the green indicator of the instrument is extinguished, but the measurement temperature is still rising. The main control output of the instrument is the SSR (level) and the controlled circuit is a solid state relay.

Inspection Method:

(1) When the meter is not energized, put the multimeter's resistance on the 1KΩ file, and use the two multimeters 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 ∞, it indicates that the solid state relay is in good condition when it is cold.

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

(2) When the instrument is powered on, when the instrument is running, when the measured temperature is higher than the set temperature and is greater than 10°C, the green indicator light of the indicator is off, the multimeter is placed on the DC voltage 20V file, and the two meters on the multimeter are used. Bars are on both ends of the instrument's main control output, but the positive and negative sides must be clarified, and the multimeter displays the voltage value.

1 If a 12V DC voltage is displayed on the multimeter, there is a problem with the instrument and the instrument should be replaced.

2 If no voltage value is displayed on the multimeter, the meter is in good condition. Then check the solid state relay. The method is to dismantle the solid state relay screws and the outside world before power is applied. After power-on, place the multimeter on the resistance×1KΩ file, and use the two multimeters of the multimeter on the two large screws of the solid state relay. If the multimeter shows the resistance value and the resistance value is very small, it indicates that the solid state relay is short-circuited in the hot state. To replace solid-state relays. On the other hand, when the resistance value is large, it indicates that the solid state relay is in good condition when it is cold.

Third, pulse output temperature control instrument main fault method

1. If the condition of the thermocouple or thermal resistor is in good condition and the instrument wiring is correct, the instrument will not heat up after being energized, or even measure the phenomenon of temperature drop (set temperature is higher than the measurement temperature precondition).

When the main control output of the instrument is a pulse output, the circuit uses a triac. First, what should be the master output of the instrument? The master output of the instrument is a pulse signal.

Inspection Method:

When the main control output of the instrument is not connected to the outside world, place the multimeter on the DC voltage of 0.5V, and use the multimeter's two meter sticks to press the power on the instrument's main control output terminal (find positive and negative). The constant temperature is higher than the measured temperature.) If the multimeter shows a slight voltage, the meter has a pulse output and the meter output is normal. When the contemporary number is G (or unsigned), the main control output is whether the small thyristor in the meter is conductive or not. . All the wires connected to the outside world on the output terminal of the instrument are removed. Place the multimeter on the resistance×1Ω file. When the power is on, the indicator light of the instrument is on (the instrument setting temperature is higher than the measurement temperature), and the multimeter shows a smaller resistance value. The master control output is normal. On the contrary, there is a large value for the no-voltage and code-name M of the code M and the resistance value of this symbol, 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, the following conditions should be checked.

1) Whether the main control output of the instrument and the triac wiring are correct. Be sure to wire according to the wiring diagram indicated on the terminal block in the product instruction manual. Otherwise, it cannot be performed normally.

2) Check the quality of high-power bidirectional thyristors in the circuit

A) In the absence of power, pull the triac's control pole gently and firmly. If it looses or falls, it indicates that the triac is broken.

B) In the absence of power, use a multimeter resistance × 1Ω file, a meter stick on the multimeter is pressed on the control electrode of the triac, a stick is on the cathode, if the resistance value displayed on the multimeter is very large or not The resistance value indicates that the triac is broken. In normal conditions, the resistance value is between ≥20Ω and ≤80Ω.

C) When the instrument is not powered, first remove the high-power bidirectional thyristor anode in the circuit from the cathode to the outside world. Place the multimeter on the resistor × 1KΩ, use a multimeter on the multimeter to clamp on the triac anode, and another rod on the cathode. The multimeter will display the resistance value. 1 If the multimeter shows the resistance value ∞ When large, it shows that the triac is in good condition when it is cold. 2 If the resistance value or resistance value on the multimeter is very small, it indicates that the triac is damaged and must be replaced.

D) When the instrument is powered on, the main control output of the instrument is a pulse signal. Before the power is turned on, disconnect the connection between the main control output of the instrument and the outside world. When the instrument is powered on, put the multimeter on the 0.5V DC voltage, and the two multimeters The stick is on the two terminals of the master output (positive and negative to be clear). When the measuring temperature of the instrument is higher than the set temperature, the green indicator light of the instrument goes out. If the multimeter shows a little voltage value, it means that there is a problem with the instrument's main control output and the instrument should be replaced. If the multimeter shows no voltage, the meter is in good condition. At this point check again, first remove the connection between the anode of the triac and the cathode and the outside world. When the meter is powered on, the measured temperature is higher than the set temperature, the green indicator light of the instrument goes out, and then the multimeter is placed on the resistance×1KΩ. On the file, use a multimeter on the multimeter to hold the triac anode and the other one on the cathode. If the multimeter shows that the resistance value is very small, it means that the two-way SCR is short-circuited in the hot state. SCR. On the other hand, when the resistance value is large, it indicates that the triac is in good condition.

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