CN103592485B - Oscillograph with input resistance defencive function - Google Patents
Oscillograph with input resistance defencive function Download PDFInfo
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- CN103592485B CN103592485B CN201210294980.1A CN201210294980A CN103592485B CN 103592485 B CN103592485 B CN 103592485B CN 201210294980 A CN201210294980 A CN 201210294980A CN 103592485 B CN103592485 B CN 103592485B
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Abstract
The invention discloses a kind of oscillograph with input resistance defencive function, including：Signal input part, AFE(analog front end) amplifying circuit, AD conversion module and the control process module being sequentially connected in series, and the first input resistance and the second input resistance；Selecting switch module, for making signal input part be selectively connected the first input end or the second input of analog front circuit；Voltage sampling module, for carrying out voltage sampling to input signal and obtaining a sampling voltage；Peak detection module, for carrying out positive and negative peak detection respectively to sampling voltage and obtaining a positive peak rectified signal and a negative peak rectified signal；Modulate circuit, is processed and is exported a conditioned signal for aligning crest rectified signal and negative peak rectified signal；Control process module is additionally operable to control selections switch module and makes the second input of signal input part connection simulation frontend amplifying circuit.Technical scheme low cost, and ensure that circuit has the high bandwidth of comparison.
Description
Technical field
The present invention relates to electric variable field tests, more particularly to a kind of oscillograph with input resistance defencive function.
Background technology
Oscillographic input has usual two kinds of input resistance patterns, low-resistance input（Generally 50 Ω or 75 Ω）And high resistant
Input（Generally 1M Ω）.Oscillographic input resistance is an oscillographic important indicator, and oscillograph is connected to circuit-under-test
Afterwards, oscillographic input resistance has reformed into a part for circuit-under-test.When 1M Ω are input into, the impact to circuit-under-test is compared
It is little, but effect of parasitic capacitance is received, and bandwidth is not high.When 50 Ω are input into, the input of 50 Ω resistance is for being 50 Ω with output impedance
Circuit-under-test carry out impedance matching, if mismatch, it may occur that signal reflex, be unfavorable for the realization of high bandwidth.50 Ω are defeated
Fashionable oscillograph bandwidth can be made thin high, have the oscillograph of tens GHz at present.
The input of high bandwidth oscilloscope can all provide 50 Ω and 1M Ω, two kinds of input resistance patterns, select for user.User
Oscillograph input resistance is selected according to the size reasonable of circuit under test output impedance, actual oscillograph input signal is in signal source
Resistance and the partial pressure of oscillograph input resistance.In general, during selection 1M Ω resistance, the amplitude of the loss of signal is minimum, but to impedance
Matching is unfavorable, and 1M Ω, when being input into, by effect of parasitic capacitance than larger, the electric capacity and 1M Ω resistance of very little can be formed by cutting
Only the relatively low low pass filter of frequency, so during general 1M Ω inputs, oscillograph bandwidth ratio is relatively low, is generally less than at present
1GHz；When selecting 50 Ω internal resistances, typically use when source impedance is 50 Ω, mainly match with source impedance, letter will not be lost
Number bandwidth.When 50 Ω are input into, oscillograph bandwidth can be made thin big, and current highest has GHz more than 30.
With reference to Fig. 1, it is the structural representation of prior art oscillograph 10, oscillograph 10 includes the signal input being sequentially connected in series
End 101, relay 102, AFE(analog front end) amplifying circuit 103, AD conversion module 104 and control process module 105, and first is defeated
Enter resistance 106 and the second input resistance 107,106 one end of the first input resistance ground connection, other end connection AFE(analog front end) are amplified
The first input end of circuit 103,107 one end of the second input resistance ground connection, other end connection simulation frontend amplifying circuit 103
The second input.Measured signal a is accessed by signal input part 101, is selectively accessing AFE(analog front end) by relay 102 and is put
The first input end or the second input of big circuit 103, if access AFE(analog front end) amplifying circuit 103 first input end namely
50 Ω input resistances are accessed, if accessing the second input of AFE(analog front end) amplifying circuit 103 namely having accessed 1M Ω inputs
The pretreatments such as resistance, measured signal a is amplified, is decayed by AFE(analog front end) amplifying circuit 103, bandwidth is limited, driving；Afterwards,
Pretreated measured signal inputs to A/D modular converters 104, carries out analog-to-digital conversion process, namely measured signal is adopted
Sample, obtains data signal, i.e. sampled data；Finally, data signal is input into control process module 105 carries out storing, triggers
The digital processings such as control, data output end output waveform display data b of control process module 105.
If selecting 50 Ω input resistances, input voltage signal to be applied directly to 50 Ω terminal resistances of oscillograph input stage
On, it is necessary to consider the rated power problem of 50 Ω resistance.The signal of such as 5V, the power on 50 Ω terminal resistances is
0.5W.Can not be infinitely great in view of the rated power of resistance, so during 50 Ω input resistances of oscillograph, needs are protected, prevent
When only user input voltage is excessive, more than the rated power of 50 Ω terminal resistances, resistance is burnt out, damage oscillograph.
The content of the invention
The technical problem to be solved is to provide a kind of oscillograph with input resistance defencive function, to oscillography
The smaller input resistance of device is effectively protected, and when preventing user input voltage excessive, is burnt out resistance, is damaged oscillograph.
Above-mentioned technical problem is solved, the present invention provides a kind of oscillograph with input resistance defencive function, including：Successively
The signal input part of series connection, AFE(analog front end) amplifying circuit, AD conversion module and control process module, and the first input resistance and
Second input resistance；Described first input resistance one end ground connection, of other end connection simulation frontend amplifying circuit are first defeated
Enter end, the second input resistance one end ground connection, second input of other end connection simulation frontend amplifying circuit are described
First input resistance is less than second input resistance；Also include：One selecting switch module, for making the signal input part
It is selectively connected the first input end or the second input of the analog front circuit；One voltage sampling module, for working as
When the signal input part connects the first input end of the AFE(analog front end) amplifying circuit, voltage sampling is carried out simultaneously to input signal
Obtain a sampling voltage；One peak detection module, for carrying out positive and negative peak detection to the sampling voltage respectively and obtaining
To a positive peak rectified signal and a negative peak rectified signal；One modulate circuit, for believing to the positive crest detection
Number and negative peak rectified signal carry out subtraction and low-pass filtering treatment and export a conditioned signal；The control process module is also
Comparative result for obtaining the virtual value of the conditioned signal the virtual value according to the conditioned signal and a threshold value comes
The selecting switch module action is controlled, when the virtual value of the conditioned signal is more than the threshold value, the selection is controlled and is opened
Closing module action makes the signal input part connect the second input of the AFE(analog front end) amplifying circuit.
As an example, the peak detection module has a cut-off frequency, and the peak detection module includes one
Individual positive peak detecting circuit and a negative peak detecting circuit；When frequency the cutting more than peak-detector circuit of the input signal
Only during frequency, the positive peak rectified signal is that the positive peak detecting circuit carries out to sampling voltage that peak detection is obtained
Individual positive crest envelope signal；The negative peak rectified signal is that the negative peak detecting circuit carries out peak detection to sampling voltage
The negative wave paddy envelope signal for obtaining；
When the frequency of the input signal is less than the cut-off frequency of peak-detector circuit, the positive peak rectified signal is
The positive peak detecting circuit carries out the positive crest rectified signal that rectification is obtained to sampling voltage；The negative peak detection letter
Number it is a negative wave paddy rectified signal that the negative peak detecting circuit carries out that to sampling voltage rectification is obtained.
As an example, the positive peak detecting circuit includes an input, output end, the one or two pole
Pipe, first electric capacity and a first resistor, the anode of first diode connect the defeated of the positive peak detecting circuit
Enter end, the negative electrode of the first diode connects the output end of the positive peak detecting circuit, and one end of first electric capacity is grounded, separately
One end connects the negative electrode of the first diode, and one end ground connection of the first resistor, the other end connect the negative electrode of the first diode；
The negative peak detecting circuit includes an input, an output end, second diode, one it is second electric
Hold and a second resistance；The anode of second diode connects the input of the negative peak detecting circuit, the two or two pole
The negative electrode of pipe connects the output end of the negative peak detecting circuit；One end ground connection of second electric capacity, other end connection second
The negative electrode of diode；One end ground connection of the second resistance, the other end connect the negative electrode of the second diode.
As an example, the modulate circuit includes：One subtraction circuit, for the positive peak rectified signal and
Negative peak rectified signal is carried out subtracting each other and obtains a positive envelope output signal；One low-pass filter circuit, for the positive closure
Network output signal is filtered, and obtains the conditioned signal.
As an example, the modulate circuit include one first follow circuit, one second follow circuit, one subtract
Method circuit and a low-pass filter circuit, described first follow circuit for will the positive peak detecting circuit and the subtraction electricity
Road is isolated, and described second follows circuit for the negative peak detecting circuit is isolated with the subtraction circuit, institute
Subtraction circuit is stated for carrying out subtracting each other and just obtaining one to the positive crest envelope detection signal and negative wave paddy envelope detection signal
Envelope output signal, the low-pass filter circuit obtain the conditioning letter for being filtered to the positive envelope output signal
Number.
As an example, described first follow circuit and second follow circuit be be made up of amplifier follow electricity
Road.
As an example, the control process module, including：
One AD conversion unit, for sampling to the conditioned signal, obtains sampled data；
One computing unit, for virtual value calculating is carried out to the sampled data in Preset Time, obtains the conditioning letter
Number virtual value, and the virtual value is compared with a threshold value, when virtual value is more than the threshold value, exports a control
Signal；
One control unit, makes the signal defeated for controlling the selecting switch module action according to the control signal
Enter the second input of the end connection Simulation scale-up circuit.
As an example, the AD conversion unit and the computing unit are made up of a single-chip microcomputer.
As an example, the first input resistance is 50 Europe, and the second input resistance is 1M Europe.
As an example, the first input resistance is 75 Europe, and the second input resistance is 1M Europe.
Technical scheme carries out voltage sampling by the input signal for contrasting less input resistance, after sampling
Signal peak detection carried out to the signal after the sampling using a peak detection module obtain positive peak detection letter
Number and a negative peak rectified signal, then through signal conditioning circuit by above-mentioned positive peak rectified signal and the inspection of negative peak
Ripple signal carries out subtraction and low-pass filtering treatment and exports a conditioned signal, obtains conditioned signal by control process module
Virtual value and according to the comparative result of the virtual value and a threshold value controlling the selecting switch module action, when the conditioning
When the virtual value of signal is more than the threshold value, controlling the selecting switch module action makes the signal input part connect the mould
Intend the second input of amplifying circuit, that is, be switched to big input resistance, so as to the input resistance little to oscillograph serves guarantor
The effect of shield.Technical scheme low cost, and ensure that circuit has the high bandwidth of comparison.
Description of the drawings
Fig. 1 is the structural representation of prior art oscillograph 10
Fig. 2 is a kind of structural representation of the oscillograph 20 with input resistance defencive function of the preferred embodiment of the present invention
Fig. 3 is a kind of structural representation of the oscillograph 30 with input resistance defencive function of the preferred embodiment of the present invention
Fig. 4 is the flow chart that the preferred embodiment of the present invention calculates conditioned signal virtual value
Fig. 5 is a kind of structural representation of the oscillograph 40 with input resistance defencive function of the preferred embodiment of the present invention
Specific embodiment
The present invention will be further described in detail with reference to the accompanying drawings and detailed description.
Embodiment 1：With reference to Fig. 2, the oscillograph 20 in the present embodiment includes signal input part 201, the simulation being sequentially connected in series
Frontend amplifying circuit 202, AD conversion module 203 and control process module 204, and the first input resistance 205 and the second input
Resistance 206；First input resistance, 205 one end is grounded, the first input end of other end connection simulation frontend amplifying circuit 202, the
Two input resistances, 206 one end is grounded, the second input of other end connection simulation frontend amplifying circuit 202, the first input resistance
205 are less than the second input resistance 206, and in the present embodiment, the first input resistance is 50 ohm, and the second input resistance is 1M ohms；Quilt
Survey the pretreatments such as signal is amplified, is decayed by AFE(analog front end) amplifying circuit 202, bandwidth is limited, driven；Afterwards, it is preprocessed
Measured signal input to A/D modular converters 203, carry out analog-to-digital conversion process, namely measured signal sampled, counted
Word signal, i.e. sampled data；Finally, data signal is input into control process module 204 carries out storing, triggers the numerals such as control
Process, the data output end output waveform display data of control process module 204..Oscillograph 20 also includes：One selecting switch
Module 207, for make the signal input part 201 be selectively connected the analog front circuit 202 first input end or
Second input, the selecting switch module 207 in the present embodiment select relay；One voltage sampling module 208, for working as
When stating signal input part 201 and connecting the first input end of the AFE(analog front end) amplifying circuit 202, voltage is carried out to input signal and is taken
Sample simultaneously obtains a sampling voltage；One peak detection module 209, for carrying out positive negative peak inspection respectively to the sampling voltage
Ripple simultaneously obtains a positive peak rectified signal and a negative peak rectified signal；One modulate circuit 210, for the positive wave
Peak rectified signal and negative peak rectified signal carry out subtraction and low-pass filtering treatment and export a conditioned signal；At the control
Reason module 204 is additionally operable to obtain the virtual value of the conditioned signal and the virtual value according to the conditioned signal and a threshold value
Comparative result controlling 207 action of selecting switch module, when the virtual value of the conditioned signal is more than the threshold value, control
Making 207 action of selecting switch module makes the signal input part 201 connect the second of the AFE(analog front end) amplifying circuit 202
Input.
Embodiment 2：With reference to Fig. 3, the oscillograph 30 in the present embodiment includes signal input part 301, the simulation being sequentially connected in series
Frontend amplifying circuit 302, AD conversion module 303 and control process module 304, and the first input resistance 305 and the second input
Resistance 306；First input resistance, 305 one end is grounded, the first input end of other end connection simulation frontend amplifying circuit 302, the
Two input resistances, 306 one end is grounded, the second input of other end connection simulation frontend amplifying circuit 302, the first input resistance
305 are less than the second input resistance 306, and in the present embodiment, the first input resistance is 50 ohm, and the second input resistance is 1M ohms；Quilt
Survey the pretreatments such as signal is amplified, is decayed by AFE(analog front end) amplifying circuit 302, bandwidth is limited, driven；Afterwards, it is preprocessed
Measured signal input to A/D modular converters 303, carry out analog-to-digital conversion process, namely measured signal sampled, counted
Word signal, i.e. sampled data；Finally, data signal is input into control process module 304 carries out storing, triggers the numerals such as control
Process, the data output end output waveform display data of control process module 304.Oscillograph 30 also includes：One selecting switch
Module 307, for make the signal input part 301 be selectively connected the analog front circuit 302 first input end or
Second input, the selecting switch module 307 in the present embodiment select relay；One voltage sample circuit 308, for working as
When stating signal input part 301 and connecting the first input end of the AFE(analog front end) amplifying circuit 302, voltage is carried out to input signal and is taken
Sample simultaneously obtains a sampling voltage, and the voltage sampling module 308 in the present embodiment is the partial pressure being made up of two resistance R2 and R2
Circuit is constituted, and after resistance R1 and resistance R2 is connected in series with each other, one end is connected on 50 Ω signals, other end ground connection, resistance
Output point of the intermediate point that R1 and resistance R2 are connected with each other as sampling voltage, wherein select the value of R1 to be far longer than 50 Ω, one
As more than tens k Ω of value, so as to the impact to 50 Ω terminal resistances can almost be ignored, do not affect 50 Ω resistance be input into when
Impedance matching and bandwidth；One peak detection module, the peak detection module include a positive peak detecting circuit 309 and
Individual negative peak detecting circuit 310, the peak detection module have a cut-off frequency, when the frequency of the input signal is more than
During the cut-off frequency of peak-detector circuit, the positive peak detecting circuit 309 carries out peak detection to sampling voltage and obtains one
Positive crest envelope signal；The negative peak detecting circuit 310 carries out peak detection and obtains a negative wave paddy envelope to sampling voltage
Signal；When the frequency of the input signal is less than the cut-off frequency of peak-detector circuit, the positive peak detecting circuit 309 pairs
Sampling voltage carries out rectification and obtains a positive crest rectified signal；The negative peak detecting circuit 310 carries out whole to sampling voltage
Stream obtains a negative wave paddy rectified signal.Positive peak detecting circuit 309 in the present embodiment includes an input, an output
The anode connection positive peak detecting circuit 309 at end, diode D1, an electric capacity C3 and a resistance R3, diode D1
Input, the output end of the negative electrode connection positive peak detecting circuit 309 of diode D1, one end ground connection of electric capacity C3, the other end connect
The negative electrode of diode D1 is connect, one end ground connection of resistance R3, the other end connect the negative electrode of diode D1；Negative peak in the present embodiment
Detecting circuit 310 includes an input, an output end, diode D2, an electric capacity C4 and a resistance R4；Two poles
The anode of pipe D2 connects the output end of the negative peak detecting circuit 310, and the negative electrode of diode D2 connects the negative peak detection
The input of circuit 310；One end ground connection of electric capacity C4, the other end connect the anode of diode D2；One termination of the resistance R4
Ground, the other end connect the anode of diode D2.The modulate circuit 312 of the present embodiment includes subtraction circuit 313 and LPF electricity
Road 314, the output end of the positive peak detecting circuit 309 connect an input of subtraction circuit 313, negative peak detecting circuit
310 output end connects another input of subtraction circuit 313, the output end connection low-pass filter circuit of subtraction circuit 313
314 input, when the frequency of input signal is more than the cut-off frequency of peak-detector circuit, positive peak detecting circuit 309 pairs
Sampling voltage carries out peak detection and obtains a positive crest envelope signal；Negative peak detecting circuit 310 carries out peak to sampling voltage
Value detection obtains a negative wave paddy envelope signal；The positive crest envelope signal of the subtraction circuit 313 pairs and negative wave paddy envelope
Signal does subtraction, positive crest envelope signal is deducted negative wave paddy envelope signal and obtains a positive envelope output signal；When input letter
Number frequency less than peak-detector circuit cut-off frequency when, the positive peak detecting circuit 309 carries out rectification to sampling voltage
Obtain a positive crest rectified signal；The negative peak detecting circuit 310 carries out rectification and obtains a negative wave paddy to sampling voltage
Rectified signal；The positive crest rectified signal of the subtraction circuit 313 pairs and negative wave paddy rectified signal do subtraction, will be positive crest whole
Stream signal deducts negative wave paddy rectified signal and obtains a positive envelope output signal.Due to the AD conversion unit in control process module
Sample rate it is certain, so needing the high frequency in the positive envelope output signal that subtraction circuit 313 exports by low-pass filter circuit 314
Component is filtered, and is made the bandwidth of positive envelope output signal of output less than the half of the sample rate of AD conversion unit, is realized anti-aliasing
Filtering, and export a conditioned signal.
Control process module 304, including：One AD conversion unit, for sampling to the conditioned signal, is adopted
Sample data；One computing unit, for virtual value calculating is carried out to the sampled data in Preset Time, obtains the conditioned signal
Virtual value, and the virtual value is compared with a threshold value, when virtual value is more than the threshold value, exports a control letter
Number；Control process module 304 also includes a control unit, for controlling the selecting switch module according to the control signal
Action makes the signal input part connect the second input of the Simulation scale-up circuit.In order to cost-effective, in the present embodiment
AD conversion unit and computing unit completed by a single-chip microcomputer for being internally integrated ADC, single-chip microcomputer needs to arrange suitable
Sample rate, gathering a number of sampled point carries out virtual value calculating, then judges what result of calculation and needs were protected
Voltage result of calculation.Due to frequency input signal it is relatively low when, peak detection electric capacity is not filtered, and single-chip microcomputer needs as far as possible to calculate complete
The signal in cycle, in the case where single-chip microcomputer inner buffer circuit is certain, needs to reduce sample rate as far as possible, in making conditioned signal
Low frequency signal can be calculated virtual value.50Hz signal frequencies to for example be met, single-chip microcomputer inner buffer has at 256 points, then needs
Sample rate f to be arranged<256*50=12.8kHz.Sample rate is determined in this way.
With reference to Fig. 4, it is the flow chart of preferred embodiment of the present invention calculating conditioned signal virtual value, if calculative sampling
Data are 256 points, and program circuit starts, and initialize single-chip microcomputer, then by result of calculation Q of computing unit（That is virtual value）Clearly
Zero, ith sample value is then read, divided by 256, result of calculation Qi for obtaining will be added with Q, be will add up after sampled value square
Result be updated to Q values；Then judge whether to have calculated at 256 points, if it did not, continuing to calculate；If having calculated at 256 points, will
As a result Q and need value to be protected（Threshold value）It is compared, this needs value to be protected, can be by 50 Ω of oscillograph input electricity
During resistance, input direct-current test is obtained.If greater than the value of protection, then computing unit output control signal is to notify control process
The control unit of module 304, input voltage are excessive, need protection, if the no more than value of protection, returns, Q is reset, weight
Newly calculated.The control unit of control process module 304 is needed relay immediately after the control signal for receiving single-chip microcomputer
1M Ω states are switched to, then control relay action makes the signal input part connect the second input of the Simulation scale-up circuit
End；Carry out being input into the related prompting transfinited simultaneously on oscillograph interface.For quick response, the control of control process module 304
Unit processed typically adopts logic circuit, and for example, during the control unit output 1 of control process module 304, relay switches to 1M
Ω, the realization of logic circuit, the relay that can be arranged user arrange state and single-chip microcomputer output and carry out and operation, and input is big
When threshold value, single-chip microcomputer output 1.When then needing to protect little input resistance, by with logic, control process module
Relay is switched to 1M Ω by 304 control unit output level 1.If do not protected, single-chip microcomputer is output as 0, by with patrol
Volume, the control unit of control process module 304 is output as the state of user's setting.
Embodiment 3, with reference to Fig. 5, the oscillograph 40 in the present embodiment includes signal input part 401, the simulation being sequentially connected in series
Frontend amplifying circuit 402, AD conversion module 403 and control process module 404, and the first input resistance 405 and the second input
Resistance 406；First input resistance, 405 one end is grounded, the first input end of other end connection simulation frontend amplifying circuit 402, the
Two input resistances, 406 one end is grounded, the second input of other end connection simulation frontend amplifying circuit 402, the first input resistance
405 are less than the second input resistance 406, and in the present embodiment, the first input resistance is 75 ohm, and the second input resistance is 1M ohms；Quilt
Survey the pretreatments such as signal is amplified, is decayed by AFE(analog front end) amplifying circuit 402, bandwidth is limited, driven；Afterwards, it is preprocessed
Measured signal input to A/D modular converters 403, carry out analog-to-digital conversion process, namely measured signal sampled, counted
Word signal, i.e. sampled data；Finally, data signal is input into control process module 404 carries out storing, triggers the numerals such as control
Process, the data output end output waveform display data of control process module 404..Oscillograph 40 also includes：One selecting switch
Module 407, for make the signal input part 401 be selectively connected the analog front circuit 402 first input end or
Second input, the selecting switch module 407 in the present embodiment select relay；One voltage sampling module 408, for working as
When stating signal input part 401 and connecting the first input end of the AFE(analog front end) amplifying circuit 402, voltage is carried out to input signal and is taken
Sample simultaneously obtains a sampling voltage；One peak detection module, the peak detection module include a positive peak detecting circuit
409 and a negative peak detecting circuit 410, the peak detection module has a cut-off frequency, when the input signal
When frequency is more than the cut-off frequency of peak-detector circuit, the positive peak detecting circuit 409 carries out peak detection to sampling voltage
Obtain a positive crest envelope signal；The negative peak detecting circuit 410 sampling voltage is carried out peak detection obtain one bear
Trough envelope signal；When the frequency of the input signal is less than the cut-off frequency of peak-detector circuit, the positive peak detection
Circuit 409 carries out rectification and obtains a positive crest rectified signal to sampling voltage；410 pairs of sampling electricity of the negative peak detecting circuit
Pressure carries out rectification and obtains a negative wave paddy rectified signal.The modulate circuit 412 of the present embodiment includes buffer circuit 415 and buffering electricity
Road 416, and subtraction circuit 413 and low-pass filter circuit 414, the output end of the positive peak detecting circuit 409 by first with
Connect an input of subtraction circuit 413 with circuit 415, the output end of negative peak detecting circuit 410 follows electricity by second
Road 416 connects another input of subtraction circuit 413, and first follows circuit 415 and second to follow circuit 416 by peak detection
Circuit is isolated with circuit below, it is to avoid other circuits affect the load of detecting circuit, so as to affect the output of detecting circuit.
First follow circuit 415 and second follow circuit 416 be be made up of amplifier follow circuit.The output of subtraction circuit 413
The input of end connection low-pass filter circuit 414, when the frequency of input signal is more than the cut-off frequency of peak-detector circuit, just
Peak-detector circuit 409 carries out peak detection and obtains a positive crest envelope signal to sampling voltage；Negative peak detecting circuit 410
Peak detection is carried out to sampling voltage and obtains a negative wave paddy envelope signal；The positive crest envelope of the subtraction circuit 413 pairs
Signal and negative wave paddy envelope signal do subtraction, obtain an absolute value signal；When the frequency of input signal is less than peak detection electricity
During the cut-off frequency on road, the positive peak detecting circuit 409 carries out rectification and obtains a positive crest rectified signal to sampling voltage；
The negative peak detecting circuit 410 carries out rectification and obtains a negative wave paddy rectified signal to sampling voltage；The subtraction circuit 413
Subtraction is done to the positive crest rectified signal and negative wave paddy rectified signal, an absolute value signal is obtained.Due to control process mould
The sample rate of the AD conversion unit in block is certain, so needing the positive envelope that subtraction circuit 413 is exported by low-pass filter circuit 414
High fdrequency component in output signal is filtered, and makes the bandwidth of positive envelope output signal of output less than the sample rate of AD conversion unit
Half, realizes anti-aliasing filter, and exports a conditioned signal.Control process module 404, including：One AD conversion unit, uses
In sampling to the conditioned signal, sampled data is obtained；One computing unit, for the sampled data in Preset Time
Virtual value calculating is carried out, the virtual value of the conditioned signal is obtained, and the virtual value is compared with a threshold value, effective
When value is more than the threshold value, a control signal is exported；Control process module 404 also includes a control unit, for foundation
The control signal controls the selecting switch module action makes the signal input part connect the of the Simulation scale-up circuit
Two inputs.
The present invention is as a result of peak-detector circuit so that input signal can be calculated in high and low frequency effectively
Value, hence in so that the responsive bandwidth of circuit can carry out the protection of input resistance than larger to the input signal of higher frequency；By
Common diode, low bandwidth amplifier and single-chip microcomputer be have selected in the present invention, therefore circuit cost is than relatively low.
Above-described is only the preferred embodiments of the present invention, and the explanation of should be understood that preferred embodiment above is only
It is to be used to help understand the method for the present invention and its core concept, the protection domain being not intended to limit the present invention is all at this
Any modification for being made within bright thought and principle, equivalent etc., should be included within the scope of the present invention.
Claims (10)
1. a kind of oscillograph with input resistance defencive function, including：The signal input part that is sequentially connected in series, AFE(analog front end) amplify
Circuit, AD conversion module and control process module, and the first input resistance and the second input resistance；First input resistance
One end is grounded, and the first input end of other end connection simulation frontend amplifying circuit, the second input resistance one end ground connection are another
Second input of end connection simulation frontend amplifying circuit, first input resistance are less than second input resistance；Which is special
Levy and be, also include：
One selecting switch module, for making the signal input part be selectively connected the of the AFE(analog front end) amplifying circuit
One input or the second input；
One voltage sampling module, for connecting the first input end of the AFE(analog front end) amplifying circuit when the signal input part
When, voltage sampling is carried out to input signal and a sampling voltage is obtained；
One peak detection module, for carrying out positive and negative peak detection respectively to the sampling voltage and obtaining a positive peak inspection
Ripple signal and a negative peak rectified signal；
One modulate circuit, for carrying out at subtraction and LPF to the positive peak rectified signal and negative peak rectified signal
Manage and export a conditioned signal；
The control process module is additionally operable to the virtual value for obtaining the conditioned signal the virtual value according to the conditioned signal
The selecting switch module action is controlled with the comparative result of a threshold value, when the virtual value of the conditioned signal is more than described
During threshold value, controlling the selecting switch module action makes the signal input part connect the second of the AFE(analog front end) amplifying circuit
Input.
2. oscillograph according to claim 1, it is characterised in that the peak detection module has a cut-off frequency,
The peak detection module includes a positive peak detecting circuit and a negative peak detecting circuit；
When the frequency of the input signal is more than the cut-off frequency of peak-detector circuit, the positive peak rectified signal is described
Positive peak detecting circuit carries out the positive crest envelope signal that peak detection is obtained to sampling voltage；The negative peak detection letter
Number it is a negative wave paddy envelope signal that the negative peak detecting circuit carries out that to sampling voltage peak detection is obtained；
When the frequency of the input signal is less than the cut-off frequency of peak-detector circuit, the positive peak rectified signal is described
Positive peak detecting circuit carries out the positive crest rectified signal that rectification is obtained to sampling voltage；The negative peak rectified signal is
The negative peak detecting circuit carries out the negative wave paddy rectified signal that rectification is obtained to sampling voltage.
3. oscillograph according to claim 2, it is characterised in that
The positive peak detecting circuit include an input, an output end, first diode, first electric capacity and
One first resistor, the anode of first diode connect the input of the positive peak detecting circuit, the first diode
Negative electrode connects the output end of the positive peak detecting circuit, and one end ground connection of first electric capacity, the other end connect the one or two pole
The negative electrode of pipe, one end ground connection of the first resistor, the other end connect the negative electrode of the first diode；
The negative peak detecting circuit includes an input, an output end, second diode, second electric capacity and
One second resistance；The anode of second diode connects the input of the negative peak detecting circuit, the second diode
Negative electrode connects the output end of the negative peak detecting circuit；One end ground connection of second electric capacity, the other end connect the two or two pole
The negative electrode of pipe；One end ground connection of the second resistance, the other end connect the negative electrode of the second diode.
4. oscillograph according to claim 2, it is characterised in that
The modulate circuit includes：
One subtraction circuit, obtains a positive closure for carrying out subtracting each other to the positive peak rectified signal and negative peak rectified signal
Network output signal；
One low-pass filter circuit, for being filtered to the positive envelope output signal, obtains the conditioned signal.
5. oscillograph according to claim 2, it is characterised in that
The modulate circuit include one first follow circuit, one second follow circuit, a subtraction circuit and a low pass
Filter circuit, described first follows circuit for the positive peak detecting circuit is isolated with the subtraction circuit, described
Second follows circuit for the negative peak detecting circuit is isolated with the subtraction circuit, and it is right that the subtraction circuit is used for
The positive crest envelope signal and negative wave paddy envelope signal are carried out subtracting each other and obtain a positive envelope output signal, the LPF
Circuit obtains the conditioned signal for being filtered to the positive envelope output signal.
6. oscillograph according to claim 5, it is characterised in that described first follows circuit and second to follow the circuit to be
What is be made up of amplifier follows circuit.
7. oscillograph according to claim 1, it is characterised in that the control process module, including：
One AD conversion unit, for sampling to the conditioned signal, obtains sampled data；
One computing unit, for virtual value calculating is carried out to the sampled data in Preset Time, obtains the conditioned signal
Virtual value, and the virtual value is compared with a threshold value, when virtual value is more than the threshold value, export a control letter
Number；
One control unit, makes the signal input part for controlling the selecting switch module action according to the control signal
Connect the second input of the AFE(analog front end) amplifying circuit.
8. oscillograph according to claim 7, it is characterised in that the AD conversion unit and the computing unit are by same
Individual single-chip microcomputer is constituted.
9. oscillograph according to claim 1, it is characterised in that the first input resistance is 50 Europe, the second input resistance is
1M Europe.
10. oscillograph according to claim 1, it is characterised in that the first input resistance is 75 Europe, the second input resistance is
1M Europe.
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| CN106383293B (en) * | 2016-10-19 | 2023-08-29 | 成都云处方科技有限责任公司 | Electrotherapy instrument with output electrode open-short circuit detection function and detection method |
| CN106569021B (en) * | 2016-10-20 | 2023-08-01 | 成都前锋电子仪器有限责任公司 | Signal conditioning circuit for radio frequency power reflectometer |
| CN112014611B (en) * | 2020-10-16 | 2021-01-15 | 深圳市鼎阳科技股份有限公司 | Digital oscilloscope and data detection method thereof |
| CN113075439A (en) * | 2021-06-04 | 2021-07-06 | 深圳市鼎阳科技股份有限公司 | Input impedance protection circuit and method of digital oscilloscope and digital oscilloscope |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6529355B1 (en) * | 2000-06-27 | 2003-03-04 | National Instruments Corporation | Input protection circuit implementing a voltage limiter |
| CN102062798A (en) * | 2009-11-17 | 2011-05-18 | 北京普源精电科技有限公司 | Oscilloscope with high-speed ADC (Analog-Digital Conversion) chips |
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|---|---|---|---|---|
| JPH0317561A (en) * | 1989-06-14 | 1991-01-25 | Seiko Epson Corp | Over input protective function of oscilloscope |
| US8488288B2 (en) * | 2008-06-27 | 2013-07-16 | National Instruments Corporation | Input protection method with variable tripping threshold and low parasitic elements |
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2012
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6529355B1 (en) * | 2000-06-27 | 2003-03-04 | National Instruments Corporation | Input protection circuit implementing a voltage limiter |
| CN102062798A (en) * | 2009-11-17 | 2011-05-18 | 北京普源精电科技有限公司 | Oscilloscope with high-speed ADC (Analog-Digital Conversion) chips |
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