CN106096463B - A kind of tamper-evident detection system and method based on capacitance detecting principle - Google Patents
A kind of tamper-evident detection system and method based on capacitance detecting principle Download PDFInfo
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- CN106096463B CN106096463B CN201610400135.6A CN201610400135A CN106096463B CN 106096463 B CN106096463 B CN 106096463B CN 201610400135 A CN201610400135 A CN 201610400135A CN 106096463 B CN106096463 B CN 106096463B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
- G06F21/70—Protecting specific internal or peripheral components, in which the protection of a component leads to protection of the entire computer
- G06F21/86—Secure or tamper-resistant housings
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- G—PHYSICS
- G07—CHECKING-DEVICES
- G07G—REGISTERING THE RECEIPT OF CASH, VALUABLES, OR TOKENS
- G07G1/00—Cash registers
- G07G1/12—Cash registers electronically operated
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Abstract
The present invention relates to a kind of tamper-evident detection systems and method based on capacitance detecting principle.The system includes including a tamper-evident protective device, a safety detection circuit；The tamper-evident protective device includes conductive contact and safety contact, and the conductive contact is connect with constant pressure source, and the safety contact is connected to the safety detection circuit, the conductive contact and safety contact split settings, to constitute an inductance capacitance；The safety detection circuit is used to carry out charge and discharge to safety contact and the charge and discharge time is detected, to judge contact situation of the safety contact with conductive contact.The present invention substitutes traditional mechanical detection on-off principle using capacitance detecting on-off principle, can not only realize the purpose of tamper-evident, but also can overcome the easy false triggering of existing apparatus, while to the higher disadvantage of structure combination required precision.
Description
Technical field
The present invention relates to a kind of tamper-evident detection systems and method based on capacitance detecting principle.
Background technique
As the important ring in finance informationalizing industry, set for electronics such as the computer of financial transaction and POS products
It is standby, the data that storage is similar to key and password has high susceptibility in this way are generally required in internal circuit plate.With electricity
The high speed development of sub- industry and computer industry, financial ITization have been deep into the every field of society.Therefore sensitive data quilt
The problem of stealing increasingly causes the great attention of the whole society.
In recent years, the side of intrusive attack can effectively be detected by having begun universal one kind in safe electronic equipment Industry
The basic principle of method, the detection method is: safety mechanical detection switch, safety mechanical detection is arranged in electronic equipment internal
Switch is made of safety contact and conductive contact.Under normal circumstances, it is tightened due to safety contact and conductive contact in mechanical structure
Close pressing, the signal on safety contact can keep connecting normal through conductive contact.When invader opens electronic equipment, safety
The electrical connection of contact and conductive contact is destroyed, and the signal on safety contact disconnects.Then equipment detects safety mechanical
Switch is triggered, and activates respective operations, as destroyed the sensitive data in equipment, record intrusion relevant information etc..
The detection method is simple and effective, but there are a problems, i.e., caused by can not effectively avoiding safety mechanical from switching
False triggering.No matter conductive contact is required between conductive contact and safety contact using the conductive devices such as carbon granule or pot son
Keep close connection.Therefore equipment is likely due to vibration, ambient temperature and humidity variation etc. in use, storage, transportational process
Reason, cause to occur between conductive contact and safety contact it is of short duration separate, and then cause equipment to destroy key and work can not be continued
Make, brings unexpected and unnecessary economic loss for user, also increase the maintenance work of producer.
In the industry in order to reduce risk caused by mechanical switch false triggering, at present there are two types of primary solutions:
One is on Design of Mechanical Structure, increase the connection stress between conductive contact and safety contact.I.e. by tight
Cooperation, conductive contact is pressed on safety contact inflexibly.Even encounter in this way it is fiercer collide with, can not also make conductive contact
It is detached from safety contact.But this design eventually improves equipment in length due to deliberately increasing the structural stress on circuit board
Failure probability in phase use process, additionally due to the program is very sensitive to package assembly precision, also to conformity of production and production
Spool control ability proposes certain requirement.
Another kind is that the signal on safety contact is filtered in hardware circuit design, when being filtered by control
Between length, generally can be to avoid overwhelming majority false triggering due to caused by vibration (as collided with and falling).But due to the program
The fortuitous event as caused by vibration cannot be distinguished and actively tear signal interruption caused by machine open as invader, actually reducing mistake
While triggering risk, the security protection ability of equipment is also reduced.
Summary of the invention
The purpose of the present invention is to provide a kind of tamper-evident detection system and method based on capacitance detecting principle, present invention benefits
Traditional mechanical detection on-off principle is substituted with capacitor detection switch principle, can not only realize the purpose of tamper-evident, but also can be overcome existing
There is the easy false triggering of device, while to the higher disadvantage of structure combination required precision.
To achieve the above object, the technical scheme is that a kind of tamper-evident detection system based on capacitance detecting principle,
Including a tamper-evident protective device, a safety detection circuit；The tamper-evident protective device includes conductive contact and safety contact, described
Conductive contact is connect with constant pressure source, and the safety contact is connected to the safety detection circuit, and the conductive contact and safety are touched
Point split settings, to constitute an inductance capacitance；The safety detection circuit is used to carry out charge and discharge and charge and discharge to safety contact
Electric time detection, to judge contact situation of the safety contact with conductive contact.
In an embodiment of the present invention, the safety detection circuit includes control circuit and fills with what the control circuit was connect
Discharge circuit, the control circuit periodically carries out charge and discharge to safety contact by charge-discharge circuit, while control circuit is logical
It spends the charge and discharge time to safety contact to detect, to judge contact situation of the safety contact with conductive contact.
In an embodiment of the present invention, the conductive contact is that conductive carbon granule or pot are young, and the safety contact covers copper for one
Pad.
In an embodiment of the present invention, the charge-discharge circuit includes hysteresis comparison circuit and push-pull amplifier circuit, described
The control terminal of hysteresis comparison circuit connects to the control circuit, and the input terminal of the hysteresis comparison circuit and safety contact are recommended and put
The output end connection of big circuit, the output end of the hysteresis comparison circuit and the input terminal of push-pull amplifier circuit connect, to constitute
RC oscillation circuit.
In an embodiment of the present invention, the control circuit judges the specific of contact situation of the safety contact with conductive contact
Mode is as follows:
Threshold voltage V1, V2 of hysteresis comparison circuit are set by control circuit, and according to the threshold voltage of stagnant comparator
The vibration frequency of V1, V2 and RC oscillation circuit, counter alarm threshold value is set,
The inductance capacitance capacitance that middle C is made of safety contact and conductive contact；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, to RC
The frequency of oscillation circuit is counted；
According to frequency statistics as a result, obtaining the cycle of oscillation number N of RC oscillation circuit, and with counter alarm threshold valueIt is compared,
If N >, then show that contact of the safety contact with conductive contact is all right；
If N <, then it is different to show that contact situation of the safety contact with conductive contact has.
The present invention also provides a kind of tamper-evident detection methods based on capacitance detecting principle, include the following steps,
S1: providing a tamper-evident protective device, a safety detection circuit, and the tamper-evident protective device includes conductive contact and peace
Full contact, the conductive contact are connect with constant pressure source, and the safety contact is connected to the safety detection circuit, the conductive touching
Head and safety contact split settings, to constitute an inductance capacitance；
S2: periodical charge and discharge are carried out to safety contact by the safety detection circuit, and safety contact is filled
Discharge time detection；
S3: it is detected according to the charge and discharge time to safety contact, obtains charging-discharging cycle, pass through what is be arranged with control circuit
Predetermined safety period threshold value is compared, if charging-discharging cycle exceeds predetermined safety period threshold range, judges conductive contact
There is exception with safety contact contact situation, finally re-execute the steps S2.
In an embodiment of the present invention, the conductive contact is that conductive carbon granule or pot are young, and the safety contact covers copper for one
Pad.
In an embodiment of the present invention, the safety detection circuit includes control circuit and fills with what the control circuit was connect
Discharge circuit, the control circuit periodically carries out charge and discharge to safety contact by charge-discharge circuit, while control circuit is logical
It spends the charge and discharge time to safety contact to detect, to judge contact situation of the safety contact with conductive contact.
In an embodiment of the present invention, the charge-discharge circuit includes hysteresis comparison circuit and push-pull amplifier circuit, described
The control terminal of hysteresis comparison circuit connects to the control circuit, and the input terminal of the hysteresis comparison circuit and safety contact are recommended and put
The output end connection of big circuit, the output end of the hysteresis comparison circuit and the input terminal of push-pull amplifier circuit connect, to constitute
RC oscillation circuit.
In an embodiment of the present invention, the step S3 judges the specific side of contact situation of the safety contact with conductive contact
Formula is as follows:
Threshold voltage V1, V2 of hysteresis comparison circuit are set by control circuit, and according to the threshold voltage of stagnant comparator
The vibration frequency of V1, V2 and RC oscillation circuit, counter alarm threshold value is set,
The inductance capacitance capacitance that middle C is made of safety contact and conductive contact；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, to RC
The frequency of oscillation circuit is counted；
According to frequency statistics as a result, obtaining the mechanical periodicity value of RC oscillation circuit, i.e. cycle of oscillation number N, and and counter
Alarm threshold valueIt is compared,
If N >, then show that contact of the safety contact with conductive contact is all right；
If N <, then it is different to show that contact situation of the safety contact with conductive contact has.
Compared to the prior art, the invention has the following advantages:
Present invention reduces the risks of safety switch false triggering, while can not also reduce the protection abilities of equipment, this
Invention detection method substitutes traditional mechanical detection on-off principle using capacitance detecting on-off principle, can both realize the mesh of tamper-evident
, and the easy false triggering of existing apparatus can be overcome, while to the higher disadvantage of structure combination required precision.
Detailed description of the invention
Fig. 1 is that the present invention is based on the tamper-evident protective device structural schematic diagrams of capacitance detecting principle.
Fig. 2 is the top view of Fig. 1.
Fig. 3 is the perspective view of Fig. 1.
Fig. 4 is safety detection circuit topology schematic diagram of the present invention.
Fig. 5 is one embodiment of the invention RC oscillating circuit waveform schematic diagram when tamper-evident protective device connects.
Fig. 6 is one embodiment of the invention RC oscillating circuit waveform schematic diagram when tamper-evident protective device disconnects.
In figure: 1 is pcb board, and 2 be the pad for connecting constant pressure source signal, and 3 be conductive contact, and 4 be safety contact.
Specific embodiment
With reference to the accompanying drawing, technical solution of the present invention is specifically described.
A kind of tamper-evident detection system based on capacitance detecting principle of the invention, including a tamper-evident protective device, a safety
Detection circuit；The tamper-evident protective device includes conductive contact 3 and safety contact 4, and the conductive contact 3 is believed with constant pressure source is connect
Number pad 2(constant pressure source signal be usually power supply signal or earth signal) connection, the safety contact 4 be connected to it is described safety inspection
Slowdown monitoring circuit, the conductive contact 3 and 4 split settings of safety contact, to constitute an inductance capacitance；The safety detection circuit is used for
Charge and discharge and the detection of charge and discharge time are carried out to safety contact, to judge contact situation of the safety contact with conductive contact.Institute
The charge-discharge circuit that safety detection circuit includes control circuit and connect with the control circuit is stated, the control circuit passes through charge and discharge
Electric circuit period property carries out charge and discharge to safety contact, while control circuit is examined by the charge and discharge time to safety contact
It surveys, to judge contact situation of the safety contact with conductive contact.
The conductive contact 3 is that conductive carbon granule or pot are young, and the safety contact 4 covers copper pad for one.
The charge-discharge circuit includes hysteresis comparison circuit and push-pull amplifier circuit, the control terminal of the hysteresis comparison circuit
It connects to the control circuit, the input terminal of the hysteresis comparison circuit is connect with the output end of safety contact, push-pull amplifier circuit, institute
The input terminal of the output end and push-pull amplifier circuit of stating hysteresis comparison circuit connects, to constitute RC oscillation circuit.The control electricity
Road judges that the concrete mode of contact situation of the safety contact with conductive contact is as follows:
Threshold voltage V1, V2 of hysteresis comparison circuit are set by control circuit, and according to the threshold voltage of stagnant comparator
The vibration frequency of V1, V2 and RC oscillation circuit, counter alarm threshold value is set,
The inductance capacitance capacitance that middle C is made of safety contact and conductive contact；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, to RC
The frequency of oscillation circuit is counted；
According to frequency statistics as a result, obtaining the cycle of oscillation number N of RC oscillation circuit, and with counter alarm threshold valueIt is compared,
If N >, then show that contact of the safety contact with conductive contact is all right；
If N <, then it is different to show that contact situation of the safety contact with conductive contact has.
The present invention also provides a kind of tamper-evident detection methods based on capacitance detecting principle, include the following steps,
S1: providing a tamper-evident protective device, a safety detection circuit, the tamper-evident protective device include conductive contact 3 with
Safety contact 4, the conductive contact 3 are usually that power supply signal or ground are believed with the pad 2(constant pressure source signal for connecting constant pressure source signal
Number) connect, the safety contact 4 is connected to the safety detection circuit, the conductive contact 3 and 4 split settings of safety contact,
To constitute an inductance capacitance；
S2: periodical charge and discharge are carried out to safety contact 4 by the safety detection circuit, and safety contact 4 is carried out
The detection of charge and discharge time；
S3: it is detected according to the charge and discharge time to safety contact 4, charging-discharging cycle is obtained, by being arranged with control circuit
Predetermined safety period threshold value be compared, if charging-discharging cycle exceed predetermined safety period threshold range, judge conductive touching
First 3, which contact situation with safety contact 4, exception, finally re-execute the steps S2.
The conductive contact is that conductive carbon granule or pot are young, and the safety contact covers copper pad for one.
The safety detection circuit includes control circuit and the charge-discharge circuit that connect with the control circuit, the control electricity
Road periodically carries out charge and discharge to safety contact by charge-discharge circuit, while control circuit passes through the charge and discharge to safety contact
Time is detected, to judge contact situation of the safety contact with conductive contact.The charge-discharge circuit includes that hysteresis compares
The control terminal of circuit and push-pull amplifier circuit, the hysteresis comparison circuit connects to the control circuit, the hysteresis comparison circuit
Input terminal is connect with the output end of safety contact, push-pull amplifier circuit, the output end of the hysteresis comparison circuit and recommends amplification
The input terminal of circuit connects, to constitute RC oscillation circuit.
The step S3 judges that the concrete mode of contact situation of the safety contact with conductive contact is as follows:
Threshold voltage V1, V2 of hysteresis comparison circuit are set by control circuit, and according to the threshold voltage of stagnant comparator
The vibration frequency of V1, V2 and RC oscillation circuit, counter alarm threshold value is set,
The inductance capacitance capacitance that middle C is made of safety contact and conductive contact；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, to RC
The frequency of oscillation circuit is counted；
According to frequency statistics as a result, obtaining the mechanical periodicity value of RC oscillation circuit, i.e. cycle of oscillation number N, and and counter
Alarm threshold valueIt is compared,
If N >, then show that contact of the safety contact with conductive contact is all right；
If N <, then it is different to show that contact situation of the safety contact with conductive contact has.
The following are specific embodiments of the present invention.
Embodiment one: as shown in figures 1 to 6, the tamper-evident detection system based on capacitance detecting principle, by tamper-evident protective device, peace
Full inspection slowdown monitoring circuit (shown in Fig. 4) is constituted；As shown in Figure 1-3, tamper-evident protective device includes that conductive contact (is used in the present embodiment and led
Electric carbon granule) with safety contact (covering copper pad in the present embodiment for what cloth was placed on circuit board internal layer), conductive contact and safety contact
Between separated by board substrate, to constitute an inductance capacitance；Conductive contact is connect with earth signal, and safety contact is connected to safety
Detection circuit；
Assuming that the capacitance of the inductance capacitance is, by taking conductive contact is conductive carbon granule as an example, since conductive carbon granule bottom surface is flat
Face, and safety contact is equally a flat surface, then the inductance capacitance can approximation be considered as a plane-parallel capacitor.Then according to parallel-plate electricity
The definition of container, the capacitance of the inductance capacitanceAre as follows:
Wherein,The dielectric constant of medium between safety contact and conductive contact, due under normal circumstances, the medium by
The insulated part (FR4 substrate and solder mask) and air of pcb board are constituted, therefore can be considered steady state value, therefore the inductance capacitance
Capacitance, only and conductive contact and safety contact equivalent areaAnd the two spacingIt is related.Any change safety contact with
The movement of conductive contact relative position finally can all be embodied in capacitanceVariation on.
There are many kinds of the method for detection capacitance is current, using sense capacitor and resistance is utilized in the present embodiment, one is formed
A RC oscillating circuit.Capacitance is obtained indirectly by measuring the frequency of RC oscillating circuit.It is specific as follows:
Safety contact is connected to hysteresis comparison circuit input terminal, the output of hysteresis comparison circuit terminates push-pull amplifier circuit,
Push-pull amplifier circuit output end takes back hysteresis comparison circuit input terminal, to constitute a positive feedback oscillation loop.
The then frequency of oscillation of the oscillation circuitAre as follows:
Wherein,For the quiescent current on the oscillation circuit,For the threshold voltage of hysteresis comparison circuitWithDifference.
Due to the threshold voltage of hysteresis comparison circuitWithIt has been determined that so a median can be found
Threshold voltage as statistics frequency of oscillation.
A counter is driven by a standard clock source, to the periodicity of statistics oscillatorIt is counted, through standard
Clock source frequencyAfter conversion, the frequency of oscillation on oscillation circuit can be obtained, to instead release direct capacitance detection switch
Equivalent capacitance valueSituation is contacted to obtain it.
Opposite, by standard time clock source frequency, the threshold value of hysteresis comparison circuitWithAnd counter report
Alert threshold valueEtc. parameters configuration, the detection sensitivity of direct capacitance detection switch can be customized, thus realize do not dropping
Under the premise of low equipment safety protective capacities, the risk of detection switch false triggering is reduced.
The specific detection method is as follows for the above-mentioned tamper-evident detection system based on capacitance detecting principle:
First by the way that software and hardware is adjusted, the standard time clock source frequency of safety detection circuit is set, hysteresis compares
The threshold voltage of circuitWithAnd median, counter alarm threshold value, then
Starting detection.
It is enabled first to be vibrated back by the RC that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted when detection
Road starts to count the frequency of RC oscillation circuit after vibrational stabilization on RC oscillation circuit.Both statistics available one when statistics
The time in period, also time in statistics available multiple periods.Finally by RC oscillator cycle of oscillation number, with preset counter
Alarm threshold valueIt is compared:
If RC oscillating circuit waveform is as shown in figure 5, sampled result N >, then illustrate that safety contact contacts situation
Well；
If RC oscillating circuit waveform is as shown in fig. 6, sampled result N <, then illustrate that safety contact contacts situation
Have different.
The advantages of embodiment, is, since the safety detection method based on direct capacitance principle belongs to non-contact detection, because
This to the contact pressure between conductive contact and safety contact and insensitive, even if due to being influenced by external environment, it is conductive
Small gap is produced between contact and safety contact, will not lead to the false triggering of safety detection circuit.And since this is anti-
The projection overlapping area taken off between the capacitance of protective device and conductive contact and safety contact changes linearly relationship, compared to conduction
Vertical interval between contact and safety contact is more insensitive, therefore can also tolerate the error of certain fit on.
The above are preferred embodiments of the present invention, all any changes made according to the technical solution of the present invention, and generated function is made
When with range without departing from technical solution of the present invention, all belong to the scope of protection of the present invention.
Claims (6)
1. a kind of tamper-evident detection system based on capacitance detecting principle, it is characterised in that: including a tamper-evident protective device, a safety
Detection circuit；The tamper-evident protective device includes conductive contact and safety contact, and the conductive contact is connect with constant pressure source, described
Safety contact is connected to the safety detection circuit, the conductive contact and safety contact split settings, to constitute an induced electricity
Hold；The safety detection circuit is used to carry out charge and discharge to safety contact and the charge and discharge time is detected, to judge safety contact
Contact situation with conductive contact；The safety detection circuit includes control circuit and the charge and discharge connecting with control circuit electricity
Road, the control circuit periodically carries out charge and discharge to safety contact by charge-discharge circuit, while control circuit passes through to peace
The charge and discharge time of full contact is detected, to judge contact situation of the safety contact with conductive contact；The charge and discharge electricity
Road includes hysteresis comparison circuit and push-pull amplifier circuit, and the control terminal of the hysteresis comparison circuit connects to the control circuit, described
The input terminal of hysteresis comparison circuit is connect with the output end of safety contact, push-pull amplifier circuit, the hysteresis comparison circuit it is defeated
The input terminal of outlet and push-pull amplifier circuit connection, to constitute RC oscillation circuit.
2. a kind of tamper-evident detection system based on capacitance detecting principle according to claim 1, it is characterised in that: described to lead
Electrical contact is that conductive carbon granule or pot are young, and the safety contact covers copper pad for one.
3. a kind of tamper-evident detection system based on capacitance detecting principle according to claim 1, it is characterised in that: the control
The concrete mode of contact situation of the circuit judges safety contact processed with conductive contact is as follows:
By control circuit be arranged hysteresis comparison circuit threshold voltage V1, V2, and according to the threshold voltage V1 of stagnant comparator,
The vibration frequency of V2 and RC oscillation circuitCounter alarm threshold value N is setthreshold, wherein C be
The inductance capacitance capacitance that safety contact and conductive contact are constituted；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, RC is vibrated
The frequency in circuit is counted；
According to frequency statistics as a result, obtaining the cycle of oscillation number N of RC oscillation circuit, and with counter alarm threshold value NthresholdInto
Row compares,
If N > Nthreshold, then show that contact of the safety contact with conductive contact is all right；
If N < Nthreshold, then it is different to show that contact situation of the safety contact with conductive contact has.
4. a kind of tamper-evident detection method based on capacitance detecting principle, it is characterised in that: include the following steps,
S1: providing a tamper-evident protective device, a safety detection circuit, and the tamper-evident protective device includes that conductive contact and safety are touched
Point, the conductive contact are connect with constant pressure source, and the safety contact is connected to the safety detection circuit, the conductive contact with
Safety contact split settings, to constitute an inductance capacitance；
S2: periodical charge and discharge are carried out to safety contact by the safety detection circuit, and charge and discharge are carried out to safety contact
Time detection；
S3: detecting according to the charge and discharge time to safety contact, obtain charging-discharging cycle, predetermined by being arranged with control circuit
Safety period threshold value is compared, if charging-discharging cycle exceeds predetermined safety period threshold range, judges conductive contact and peace
Full contact contact situation has exception, finally re-execute the steps S2；
The safety detection circuit includes control circuit and the charge-discharge circuit that connect with the control circuit, and the control circuit is logical
It crosses charge-discharge circuit and charge and discharge periodically is carried out to safety contact, while control circuit passes through the charge and discharge time to safety contact
It is detected, to judge contact situation of the safety contact with conductive contact；The charge-discharge circuit includes hysteresis comparison circuit
And push-pull amplifier circuit, the control terminal of the hysteresis comparison circuit connect to the control circuit, the input of the hysteresis comparison circuit
End is connect with the output end of safety contact, push-pull amplifier circuit, the output end and push-pull amplifier circuit of the hysteresis comparison circuit
Input terminal connection, to constitute RC oscillation circuit.
5. a kind of tamper-evident detection method based on capacitance detecting principle according to claim 4, it is characterised in that: described to lead
Electrical contact is that conductive carbon granule or pot are young, and the safety contact covers copper pad for one.
6. a kind of tamper-evident detection method based on capacitance detecting principle according to claim 4, it is characterised in that: the step
Rapid S3 judges that the concrete mode of contact situation of the safety contact with conductive contact is as follows:
By control circuit be arranged hysteresis comparison circuit threshold voltage V1, V2, and according to the threshold voltage V1 of stagnant comparator,
The vibration frequency of V2 and RC oscillation circuitCounter alarm threshold value N is setthreshold, wherein C be
The inductance capacitance capacitance that safety contact and conductive contact are constituted；Then, start safety detection circuit；
After the RC oscillation circuit vibrational stabilization that safety contact, hysteresis comparison circuit and push-pull amplifier circuit are constituted, RC is vibrated
The frequency in circuit is counted；
According to frequency statistics as a result, obtaining the mechanical periodicity value of RC oscillation circuit, i.e. cycle of oscillation number N, and alarm with counter
Threshold value NthresholdIt is compared,
If N > Nthreshold, then show that contact of the safety contact with conductive contact is all right；
If N < Nthreshold, then it is different to show that contact situation of the safety contact with conductive contact has.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610400135.6A CN106096463B (en) | 2016-06-08 | 2016-06-08 | A kind of tamper-evident detection system and method based on capacitance detecting principle |
| PCT/CN2016/094798 WO2017210996A1 (en) | 2016-06-08 | 2016-08-12 | Tamper-evident detection system and method based on capacitance detection principle |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610400135.6A CN106096463B (en) | 2016-06-08 | 2016-06-08 | A kind of tamper-evident detection system and method based on capacitance detecting principle |
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| CN106096463A CN106096463A (en) | 2016-11-09 |
| CN106096463B true CN106096463B (en) | 2019-02-19 |
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| Publication number | Publication date |
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| WO2017210996A1 (en) | 2017-12-14 |
| CN106096463A (en) | 2016-11-09 |
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