A contact resistance monitoring and alarming device for a contact

Abstract

The present invention discloses a contact resistance monitoring and alarming device for a contact point, which includes a box body, an alarming module installed on the box body, and further includes a power supply module, a monitoring module, a fixed connecting piece and a movable connecting piece. The power supply module and the monitoring module are installed inside the box body. The monitoring module and the alarming module are electrically connected to the power supply module. The fixed connecting piece is installed on the upper side of the box body and is electrically connected to the monitoring module. The movable connecting piece is located on the upper side of the box body and is electrically connected to the monitoring module through a connecting wire. The monitoring module is electrically connected to the alarming module. During monitoring, the fixed connecting piece is electrically connected to one end of the contact point to be monitored, and the movable connecting piece is electrically connected to the other end of the contact point to be monitored. The present invention is used in the equipment control loop, and can give an alarm when the contact resistance of the contact point increases, reminding the maintenance personnel to replace it in time.

Description

Technical Field

[0001] The present invention belongs to the field of industrial automatic control, and particularly relates to a contact resistance monitoring and alarming device for contacts. Background Art

[0002] Currently, in some industrial automatic control circuits, relay contacts or contactor contacts are used as conditions for equipment startup. Whether these contacts are in good contact cannot be monitored, and equipment inspection personnel cannot directly detect abnormal contact resistance of these contacts. Only when the equipment startup fails can it be found that the contact resistance of these contacts has become very large; in addition, during the operation of the equipment, the contact resistance of multiple contacts of the contactor after operation cannot be monitored either. Only when the load voltage is unbalanced and the alarm stops the machine can it be found that the contactor contacts are severely burned; both of these situations are the main causes of equipment failures. Summary of the Invention

[0003] The purpose of the present invention is to provide a contact resistance monitoring and alarming device for contacts, which is used in an equipment control circuit to give an alarm when the contact resistance of the contacts increases, reminding maintenance personnel to replace them in time.

[0004] The contact resistance monitoring and alarming device for contacts of the present invention includes a box body, an alarm module installed on the box body, and also includes a power supply module, a monitoring module, a fixed connection piece and a movable connection piece. The power supply module and the monitoring module are installed in the box body. The monitoring module and the alarm module are electrically connected to the power supply module. The fixed connection piece is installed on the upper side of the box body and is electrically connected to the monitoring module. The movable connection piece is located on the upper side of the box body and is electrically connected to the monitoring module through a connecting wire. The monitoring module is electrically connected to the alarm module; during monitoring, the fixed connection piece is electrically connected to one end of the monitored contact, the movable connection piece is electrically connected to the other end of the monitored contact, and at the same time, the box body is fixedly installed on the equipment control circuit through the fixed connection piece.

[0005] Preferably, the monitoring module includes a first resistor, a second adjustable resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a diode, a capacitor, a first comparator, a second comparator, a NOR gate, and a triode. The positive electrode of the diode serves as the first connection end of the monitoring module. The negative electrode of the diode is connected to one end of the first resistor. The other end of the first resistor is connected to a fixed end and an adjustment end of the second adjustable resistor. The adjustment knob of the second adjustable resistor is installed on the box body. The other fixed end of the second adjustable resistor is connected to one end of the capacitor, one end of the third resistor, the non-inverting input terminal of the first comparator, and the inverting input terminal of the second comparator. The other end of the capacitor and the other end of the third resistor are connected to the negative voltage output terminal of the power supply module and serve as the second connection end of the monitoring module. The positive power supply terminal of the first comparator is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The inverting input terminal of the first comparator is connected to one end of the sixth resistor and one end of the seventh resistor. The positive power supply terminal of the second comparator is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The non-inverting input terminal of the second comparator is connected to one end of the fourth resistor and one end of the fifth resistor. The other end of the fifth resistor and the other end of the seventh resistor are connected to the negative voltage output terminal of the power supply module. The other end of the fourth resistor and the other end of the sixth resistor are connected to the positive voltage output terminal of the power supply module. The output terminal of the first comparator is connected to one input terminal of the NOR gate. The output terminal of the second comparator is connected to the other input terminal of the NOR gate. The positive power supply terminal of the NOR gate is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The output terminal of the NOR gate is connected to the base of the triode. The emitter of the triode is connected to the negative voltage output terminal of the power supply module. The collector of the triode (serving as the output terminal of the monitoring module) is connected to one end of the alarm module. The other end of the alarm module is connected to the positive voltage output terminal of the power supply module.

[0006] Preferably, the monitoring module further includes a voltage selection switch. The voltage selection switch is installed on the box body and has three gears. The first resistor is one of the first eleven resistor, the first twelve resistor, and the first thirteen resistor. One ends of the first eleven resistor, the first twelve resistor, and the first thirteen resistor are all connected to the negative electrode of the diode. The other ends of the first eleven resistor, the first twelve resistor, and the first thirteen resistor can be respectively connected to the adjustment end of the second adjustable resistor through the voltage selection switch. When the voltage selection switch is turned to the first gear, the first eleven resistor (serving as the first resistor) is connected to the adjustment end of the second adjustable resistor through the voltage selection switch. When the voltage selection switch is turned to the second gear, the first twelve resistor (serving as the first resistor) is connected to the adjustment end of the second adjustable resistor through the voltage selection switch. When the voltage selection switch is turned to the third gear, the first thirteen resistor (serving as the first resistor) is connected to the adjustment end of the second adjustable resistor through the voltage selection switch.

[0007] Preferably, the fixed connection piece is electrically connected to the first connection end of the monitoring module, and the movable connection piece is electrically connected to the second connection end of the monitoring module through a connecting wire; or the fixed connection piece is electrically connected to the second connection end of the monitoring module, and the movable connection piece is electrically connected to the first connection end of the monitoring module through a connecting wire.

[0008] Preferably, the power supply module uses a battery. The positive voltage output end of the power supply module is the positive electrode of the battery, and the negative voltage output end of the power supply module is the negative electrode of the battery.

[0009] Preferably, the alarm module is composed of a speaker and an indicator light connected in parallel. The speaker and the indicator light are independently installed on the box body. Using the method of acoustic and optical alarm can more conveniently remind the maintenance personnel to replace in time when the contact resistance increases.

[0010] When the contact resistance of the monitored contact in the equipment control circuit is monitored by using the present invention, the fixed connection piece is electrically connected to one end of the monitored contact, and the movable connection piece is electrically connected to the other end of the monitored contact; if the monitored contact is in the open state, its contact resistance is very large, and there will be no alarm at this time. If the monitored contact is in the closed position and in good contact, its contact resistance is very small, and there will be no alarm at this time either. Only when the monitored contact is in the closed position but in poor contact, its contact resistance increases, will the alarm module be controlled to give an alarm, reminding the maintenance personnel to replace in time to avoid causing equipment failures; and the present invention has a simple structure and low cost. The box body is fixed through the fixed connection piece, and can realize on-line monitoring and alarm of the contact resistance of the contact, and is suitable for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic structural diagram of this embodiment.

[0012] Figure 2 is a circuit block diagram of this embodiment.

[0013] Figure 3 is a circuit schematic diagram of this embodiment. DETAILED DESCRIPTION OF THE EMBODIMENT

[0014] The following will describe this embodiment in detail with reference to the accompanying drawings.

[0015] As Figures 1 to 3 shown, the contact resistance monitoring and alarm device for the contact includes a box body 1, an alarm module, a power supply module, a monitoring module, a fixed connection piece 4 and a movable connection piece 5. The power supply module uses a 23A type 12V battery BAT. A battery box 6 is provided on the box body 1, and the battery BAT is installed in the battery box 6. The alarm module is composed of a speaker 2 and an indicator light 3 connected in parallel. The speaker 2 and the indicator light 3 are independently installed on the box body 1.

[0016] AsFigure 3As shown, the monitoring module includes a first resistor, a second adjustable resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a voltage selection switch 8, a diode D, a capacitor C, a first comparator A1, a second comparator A2, a NOR gate G, and a triode Q. The capacitor C is a polarized capacitor; the first resistor is one of the first eleven resistor R11, the first twelve resistor R12, and the first thirteen resistor R13. The voltage selection switch 8 is installed on the box body 1. The voltage selection switch 8 has three gears, which are: the first gear Ⅰ, 220V DC gear; the second gear Ⅱ, 220V AC and 110V DC gear; the third gear Ⅲ, AC below 110V and DC below 48V. The positive electrode of the diode D is used as the first connection end of the monitoring module and is electrically connected to the fixed connection piece 4. The fixed connection piece 4 is installed on the upper side of the box body 1. The negative electrode of the diode D is connected to one end of the first eleven resistor R11, the first twelve resistor R12, and the first thirteen resistor R13. The other end of the first eleven resistor R11 is connected to the static contact 81 of the voltage selection switch 8. The other end of the first twelve resistor R12 is connected to the static contact 83 of the voltage selection switch 8. The other end of the first thirteen resistor R13 is connected to the static contact 85 of the voltage selection switch 8. The static contacts 82, 84, and 86 of the voltage selection switch 8 are all connected to a fixed end and an adjustment end of the second adjustable resistor R2. The adjustment knob 7 of the second adjustable resistor R2 is installed on the box body 1. The other fixed end of the second adjustable resistor R2 is connected to the positive electrode of the capacitor C, one end of the third resistor R3, the non-inverting input terminal of the first comparator A1, and the inverting input terminal of the second comparator A2. The negative electrode of the capacitor C is connected to the negative electrode of the battery BAT and serves as the second connection end of the monitoring module and is electrically connected to the movable connection piece 5 through a connecting wire 9 (a flexible wire about 10 cm long). The movable connection piece 5 is located on the upper side of the box body 1. The other end of the third resistor R3 is connected to the negative electrode of the battery BAT. The positive power supply terminal of the first comparator A1 is connected to the positive electrode of the battery BAT. The negative power supply terminal of the first comparator A1 is connected to the negative electrode of the battery BAT. The inverting input terminal of the first comparator A1 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The other end of the sixth resistor R6 is connected to the positive electrode of the battery BAT. The other end of the seventh resistor R7 is connected to the negative electrode of the battery BAT. The positive power supply terminal of the second comparator A2 is connected to the positive electrode of the battery BAT. The negative power supply terminal of the second comparator A2 is connected to the negative electrode of the battery BAT. The non-inverting input terminal of the second comparator A2 is connected to one end of the fourth resistor R4 and one end of the fifth resistor R5. The other end of the fourth resistor R4 is connected to the positive electrode of the battery BAT. The other end of the fifth resistor R5 is connected to the negative electrode of the battery BAT.The output terminal of the first comparator A1 is connected to one input terminal of the NOR gate G, and the output terminal of the second comparator A2 is connected to the other input terminal of the NOR gate G. The positive power supply terminal of the NOR gate G is connected to the positive electrode of the battery BAT, and the negative power supply terminal of the NOR gate G is connected to the negative electrode of the battery BAT. The output terminal of the NOR gate G is connected to the base of the triode Q. The emitter of the triode Q is connected to the negative electrode of the battery BAT. The collector of the triode Q is connected to one end of the speaker 2 and one end of the indicator light 3. The other end of the speaker 2 and the other end of the indicator light 3 are connected to the positive electrode of the battery BAT. When the voltage selection switch 8 is turned to the first gear position I, the moving contact of the voltage selection switch 8 connects the stationary contact 81 and the stationary contact 82, and the first resistor R11 (as the first resistor) is connected to the adjustment terminal of the second adjustable resistor R2 through the moving contact. When the voltage selection switch 8 is turned to the second gear position II, the moving contact of the voltage selection switch 8 connects the stationary contact 83 and the stationary contact 84, and the second resistor R12 (as the first resistor) is connected to the adjustment terminal of the second adjustable resistor R2 through the moving contact. When the voltage selection switch 8 is turned to the third gear position III, the moving contact of the voltage selection switch 8 connects the stationary contact 85 and the stationary contact 86, and the third resistor R13 (as the first resistor) is connected to the adjustment terminal of the second adjustable resistor R2 through the moving contact.

[0017] There is a monitored contact K between the circuit L1 and the circuit L2 in the device control loop. During use, first, according to the applied voltage level of the device control loop, select the gear through the voltage selection switch 8. If the applied voltage of the device control loop is 220V DC, turn the voltage selection switch 8 to the first gear position I. If the applied voltage of the device control loop is 220V AC or 110V DC, turn the voltage selection switch 8 to the second gear position II. If the applied voltage of the device control loop is AC and less than or equal to 110V or DC and less than or equal to 48V, turn the voltage selection switch 8 to the third gear position III. After the gear selection is completed, connect the fixed connection piece 4 to one end (circuit L1 end) of the monitored contact K, connect the movable connection piece 5 to the other end (circuit L2 end) of the monitored contact K through the connecting wire 9, and fix the box body 1 on the device control loop through the fixed connection piece 4. Then, when the monitored contact K is in the closed position and in good contact, rotate the adjustment knob 7 to make the speaker 2 and the indicator light 3 not alarm. Then, during the use of the monitoring and alarm device, if the monitored contact K is in the closed position but has poor contact (i.e., the contact resistance increases), the speaker 2 and the indicator light 3 will alarm, and if the monitored contact K is open, the speaker 2 and the indicator light 3 will not alarm.

[0018] The monitoring and alarming principle is as follows: The voltage between the two ends of the monitored contact K is stepped down by the first resistor, rectified by the diode D, and filtered by the capacitor C to obtain the sampling voltage for measuring the contact resistance. This voltage is divided by the second adjustable resistor R2, and a sampled voltage is obtained from the third resistor R3. The sampled voltage is connected to the first comparator A1 and the second comparator A2. The threshold voltages of the first comparator A1 and the second comparator A2 are from the battery BAT. The threshold voltage of the first comparator A1 (i.e., the voltage input to the inverting input terminal of A1) is obtained by dividing the voltage by the seventh resistor R7, and the threshold voltage of the second comparator A2 (i.e., the voltage input to the non-inverting input terminal of A2) is obtained by dividing the voltage by the fifth resistor R5. The threshold voltage of the first comparator A1 is higher than the threshold voltage of the second comparator A2. When the monitored contact K is in the open state, the sampled voltage is higher than the threshold voltage of the first comparator A1, the NOR gate G outputs a low level, the triode Q is not turned on, the indicator light 3 remains off, and the speaker 2 remains closed. In this case, no alarm is output. When the monitored contact K is in the closed position and in good contact, the sampled voltage is lower than the threshold voltage of the second comparator A2, the NOR gate G outputs a low level, the triode Q is not turned on, the indicator light 3 remains off, and the speaker 2 remains closed. In this case, no alarm is output either. Only when the monitored contact K is in the closed position but with poor contact (the contact resistance increases), the sampled voltage is higher than the threshold voltage of the second comparator A2 and lower than the threshold voltage of the first comparator A1, the NOR gate G outputs a high level, the triode Q is turned on, the indicator light 3 lights up, and the speaker 2 is turned on for audible and visual alarms.

[0019] In practical applications, the size of the sampled voltage can be adjusted by rotating the adjustment knob 7. Taking the application voltage of the equipment control circuit as 48V DC as an example, the voltage selection switch 8 is turned to the third gear III. The fifth resistor R5 obtains a voltage of 1V, the threshold voltage of the second comparator A2 is 1V, the seventh resistor R7 obtains a voltage of 10V, and the threshold voltage of the first comparator A1 is 10V. If the sampled voltage is greater than 10V, it means that the monitored contact K is open and no alarm is output. If the sampled voltage is less than 1V, it means that the monitored contact K is in the closed position and in good contact and no alarm is output. If the sampled voltage is greater than 1V and less than 10V, it means that the monitored contact K is in the closed position but with poor contact (the contact resistance increases) and an alarm is output.

Claims

1. A contact resistance monitoring and alarming device for a contact point, comprising a box body (1) and an alarming module installed on the box body (1). Characterized in that: It further includes a power supply module, a monitoring module, a fixed connecting piece (4) and a movable connecting piece (5). The power supply module and the monitoring module are installed inside the box body (1). The monitoring module, the alarming module are electrically connected to the power supply module. The fixed connecting piece (4) is installed on the upper side of the box body (1) and is electrically connected to the monitoring module. The movable connecting piece (5) is located on the upper side of the box body (1) and is electrically connected to the monitoring module through a connecting wire (9). The monitoring module is electrically connected to the alarming module. The alarming module is composed of a loudspeaker (2) and an indicator light (3) connected in parallel. The loudspeaker (2) and the indicator light (3) are independently installed on the box body (1). During monitoring, the fixed connecting piece (4) is electrically connected to one end of the contact point K to be monitored, and the movable connecting piece (5) is electrically connected to the other end of the contact point K to be monitored. Wherein, the monitoring module includes a first resistor, a second adjustable resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a diode D, a capacitor C, a first comparator A1, a second comparator A2, a NOR gate G and a triode Q. The positive electrode of the diode D is used as the first connection end of the monitoring module. The negative electrode of the diode D is connected to one end of the first resistor. The other end of the first resistor is connected to a fixed end and an adjusting end of the second adjustable resistor R2. The adjusting knob (7) of the second adjustable resistor R2 is installed on the box body (1). The other fixed end of the second adjustable resistor R2 is connected to one end of the capacitor C, one end of the third resistor R3, the non-inverting input terminal of the first comparator A1 and the inverting input terminal of the second comparator A2. The other end of the capacitor C and the other end of the third resistor R3 are connected to the negative voltage output terminal of the power supply module and serve as the second connection end of the monitoring module. The positive power supply terminal of the first comparator A1 is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The inverting input terminal of the first comparator A1 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The positive power supply terminal of the second comparator A2 is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The non-inverting input terminal of the second comparator A2 is connected to one end of the fourth resistor R4 and one end of the fifth resistor R5. The other end of the fifth resistor R5 and the other end of the seventh resistor R7 are connected to the negative voltage output terminal of the power supply module. The other end of the fourth resistor R4 and the other end of the sixth resistor R6 are connected to the positive voltage output terminal of the power supply module. The output terminal of the first comparator A1 is connected to one input terminal of the NOR gate G. The output terminal of the second comparator A2 is connected to the other input terminal of the NOR gate G. The positive power supply terminal of the NOR gate G is connected to the positive voltage output terminal of the power supply module, and the negative power supply terminal is connected to the negative voltage output terminal of the power supply module. The output terminal of the NOR gate G is connected to the base of the triode Q. The emitter of the triode Q is connected to the negative voltage output terminal of the power supply module. The collector of the triode Q is connected to one end of the loudspeaker (2) and the indicator light (3). The other ends of the loudspeaker (2) and the indicator light (3) are connected to the positive voltage output terminal of the power supply module.

2. The contact resistance monitoring and alarming device for the contact according to claim 1, characterized in that: The monitoring module further includes a voltage selection switch (8), the voltage selection switch (8) is installed on the box body (1) and has three gears; the first resistor is one of the first resistor R11, the second resistor R12, and the third resistor R13. One ends of the first resistor R11, the second resistor R12, and the third resistor R13 are all connected to the negative electrode of the diode D, and the other ends of the first resistor R11, the second resistor R12, and the third resistor R13 can be respectively connected to the adjusting end of the second adjustable resistor R2 through the voltage selection switch (8); when the voltage selection switch (8) is turned to the first gear, the first resistor R11 is connected to the adjusting end of the second adjustable resistor R2 through the voltage selection switch (8); when the voltage selection switch (8) is turned to the second gear, the second resistor R12 is connected to the adjusting end of the second adjustable resistor R2 through the voltage selection switch (8); when the voltage selection switch (8) is turned to the third gear, the third resistor R13 is connected to the adjusting end of the second adjustable resistor R2 through the voltage selection switch (8).

3. The contact resistance monitoring and alarming device for the contact according to claim 2, characterized in that: The fixed connecting piece (4) is electrically connected to the first connection end of the monitoring module, and the movable connecting piece (5) is electrically connected to the second connection end of the monitoring module through a connecting wire (9).

4. The contact resistance monitoring and alarming device for the contact according to claim 2, characterized in that: The fixed connecting piece (4) is electrically connected to the second connection end of the monitoring module, and the movable connecting piece (5) is electrically connected to the first connection end of the monitoring module through a connecting wire (9).

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