CN114594416A - Millivolt-level voltage frequency conversion circuit applied to voltage source remote calibration system - Google Patents

Millivolt-level voltage frequency conversion circuit applied to voltage source remote calibration system Download PDF

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CN114594416A
CN114594416A CN202210095746.XA CN202210095746A CN114594416A CN 114594416 A CN114594416 A CN 114594416A CN 202210095746 A CN202210095746 A CN 202210095746A CN 114594416 A CN114594416 A CN 114594416A
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voltage
module
pins
level
comparator
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方立德
段思涵
李宜明
马鑫月
韦子辉
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Hebei University
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Hebei University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/28—Provision in measuring instruments for reference values, e.g. standard voltage, standard waveform
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/60—Analogue/digital converters with intermediate conversion to frequency of pulses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

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Abstract

The invention provides a millivolt-level voltage frequency conversion circuit applied to a voltage source remote calibration system. The circuit comprises a power supply module, a manual/automatic mode selection switch module, a millivolt-level voltage threshold comparison module, a logic coding module, a programmable gain operation amplification module, a voltage frequency conversion module and an amplification gain display module. The power supply module is used for providing working voltage for other modules. The manual/automatic mode selection switch module realizes the switching of two modes of manually selecting amplification gain, automatically identifying input voltage and selecting corresponding amplification gain. The millivolt voltage threshold comparison module is composed of three sets of single-limit comparators with thresholds of 1V, 100mV and 10mV respectively, and realizes that input voltage is identified in an automatic mode and corresponding signals are output to the logic coding module. The invention can realize high-precision voltage frequency conversion of millivolt-level micro voltage, and can be applied to remote calibration of a voltage source when a verification point is millivolt-level micro voltage.

Description

Millivolt-level voltage frequency conversion circuit applied to voltage source remote calibration system
Technical Field
The invention relates to the technical field of voltage frequency conversion, in particular to a millivolt-level voltage frequency conversion circuit applied to a voltage source remote calibration system.
Background
The voltage-frequency conversion circuit converts an input analog voltage signal into a pulse train and outputs the pulse train, wherein the frequency of the pulse train is in direct proportion to the amplitude of the input voltage signal. After the voltage quantity is converted into the frequency signal, the anti-interference capability of the frequency signal is enhanced, and the frequency signal is applied to the fields of voltage detection, data acquisition, communication systems and the like.
Patent No. ZL202121052817.5 discloses a remote calibration system for voltage source. The system is applied to the field of time frequency remote calibration based on a GPS common-view method, voltage signals are converted into time frequency parameters for remote calibration, the voltage signals are converted into pulse signals with corresponding frequencies through a voltage frequency conversion module, remote comparison between a standard end and a calibrated end is carried out by combining satellite signals, and remote calibration of a direct-current voltage source of a standard device which is not placed in a calibrated site is achieved. The system consists of a voltage frequency conversion module, a standard voltage source, a GPS common-view receiver, a time interval counter and a computer. The voltage frequency conversion modules at two ends of the remote laboratory and the calibration site respectively convert the voltages output by the standard voltage source and the voltage source to be calibrated into pulse signals with corresponding frequencies; the GPS common-view receivers at the two ends receive the time signals of the same GPS satellite at the same moment; time interval counters at two ends are used for measuring the time difference between the satellite synchronous second pulse output by the GPS common-view receiver and the frequency pulse signal output by the voltage frequency conversion module; data transmission is carried out between the field control computer and the remote control computer, time difference comparison and frequency comparison of pulse signals at two ends are completed through data processing, voltage comparison of a voltage source to be calibrated and a standard voltage source is further completed, a calibration result is obtained, a voltage source remote calibration process is completed, and calibration efficiency is improved.
In the remote magnitude transmission and tracing of the voltage source, the calibration difficulty of the millivolt-level tiny voltage of the detection point is higher, the precision is lower, the remote calibration of the direct-current voltage source is realized, and the measurement of the millivolt-level tiny voltage must be considered. However, the voltage-frequency conversion module related to the calibration system can only ensure the conversion accuracy when the input voltage is at voltage level, and for millivolt level voltages below 1V, the conversion accuracy and linearity are difficult to meet the accuracy requirement of the calibration system.
Disclosure of Invention
The invention aims to provide a millivolt-level voltage frequency conversion circuit applied to a voltage source remote calibration system, which is particularly suitable for voltage frequency conversion of millivolt-level tiny voltage, and has the advantages of high conversion precision, good linearity and high stability.
The invention is realized by the following steps: a millivolt level voltage frequency conversion circuit applied to a voltage source remote calibration system comprises a power supply module, a manual/automatic mode selection switch module, a millivolt level voltage threshold comparison module, a logic coding module, a programmable gain operation amplification module, a voltage frequency conversion module and an amplification gain display module;
the power supply module is connected with other modules and is used for providing working voltage for other modules;
the manual/automatic mode selection switch module is used for realizing the switching between a manual mode and an automatic mode; the manual mode refers to manually identifying input voltage and manually selecting corresponding amplification gain, and the automatic mode refers to automatically identifying input voltage and automatically selecting corresponding amplification gain;
the millivolt-level voltage threshold comparison module is respectively connected with the manual/automatic mode selection switch module and the logic coding module and is used for automatically identifying input voltage and outputting corresponding logic level to the logic coding module through three sets of single-limit comparators with threshold levels of 10mV, 100mV and 1V respectively when the manual/automatic mode selection switch module is switched to an automatic mode;
the logic coding module is respectively connected with the millivolt-level voltage threshold comparison module, the programmable gain operation amplification module and the amplification gain display module, and is used for coding the logic level output by the millivolt-level voltage threshold comparison module and outputting the corresponding logic level to the programmable gain operation amplification module and the amplification gain display module;
the programmable gain operational amplification module is respectively connected with the logic coding module and the manual/automatic mode selection switch module; in an automatic mode, the programmable gain operation amplification module amplifies the input voltage by corresponding times according to the logic level output by the logic coding module; in the manual mode, the programmable gain operation amplification module amplifies the input voltage by corresponding times according to the logic level output by the manual/automatic mode selection switch module;
the voltage frequency conversion module is connected with the programmable gain operational amplification module and is used for converting the voltage output by the programmable gain operational amplification module into corresponding frequency;
and the amplification gain display module is respectively connected with the logic coding module and the manual/automatic mode selection switch module and is used for displaying the amplification gain according to the logic level output by the logic coding module or the manual/automatic mode selection switch module.
In the above scheme, the manual/automatic mode selection switch module comprises a double-pole double-throw switch and a dial switch; the double-pole double-throw switch is provided with 6 pins, and the dial switch is provided with 4 pins; pin 1 of the double-pole double-throw switch is connected with input voltage, pin 2 is connected with +5V voltage, pins 4 and 5 are grounded, pin 3 is connected with the input end of the millivolt-level voltage threshold comparison module, and pin 6 is connected with pins 1 and 2 of the dial switch; pins 3 and 4 of the dial switch are used as output ends in a manual mode and are respectively connected with input ends of the programmable gain operation amplification module and the amplification gain display module; in a manual mode, pins 1 and 4 of the double-pole double-throw switch are communicated, and pins 2 and 6 are communicated; in the automatic mode, pins 1 and 3 of the double-pole double-throw switch are communicated, and pins 2 and 5 are communicated.
In the manual mode, when the input voltage is more than or equal to 1V, pins 1 and 4 of the dial switch are disconnected by manually shifting, and pins 2 and 3 are disconnected; when the input voltage is more than or equal to 100mV and less than 1V, manually shifting to disconnect pins 1 and 4 of the dial switch and close pins 2 and 3; when the input voltage is more than or equal to 10mV and less than 100mV, pins 1 and 4 of the dial switch are closed by manual shifting, and pins 2 and 3 are opened; when the input voltage is less than 10mV, manual toggling closes pins 1 and 4 and pins 2 and 3 of the dip switch.
In the scheme, the millivolt-level voltage threshold comparison module comprises an LM339LV chip and an external circuit consisting of a resistor and a voltage regulator tube; the LM339LV chip consists of four independent voltage comparators, and three comparators, an external resistor and a voltage stabilizing tube are utilized to form three groups of single-limit comparators;
for a first comparator with the threshold level of 1V, an input voltage is connected with the inverting input end of the first comparator through a second resistor, a 5V reference voltage is connected with the inverting input end of the first comparator through a first resistor, the output end of the first comparator is connected with the anode of a first voltage-stabilizing tube, the cathode of the first voltage-stabilizing tube is connected with the inverting input end of the first comparator, and the non-inverting input end of the first comparator is grounded through a fifth resistor; the first resistance value is 5 times of the second resistance value;
for a second comparator with the threshold level of 100mV, an input voltage is connected with the inverting input end of the second comparator through a third resistor, a 5V reference voltage is connected with the inverting input end of the second comparator through a sixth resistor, the output end of the second comparator is connected with the anode of a second voltage-stabilizing tube, the cathode of the second voltage-stabilizing tube is connected with the inverting input end of the second comparator, and the non-inverting input end of the second comparator is grounded through a fifth resistor; the sixth resistance value is 50 times of the third resistance value;
for a third comparator with the threshold level of 10mV, the input voltage is connected with the inverting input end of the third comparator through a fourth resistor, a 5V reference voltage is connected with the inverting input end of the third comparator through a seventh resistor, the output end of the third comparator is connected with the anode of a third voltage-stabilizing tube, the cathode of the third voltage-stabilizing tube is connected with the inverting input end of the third comparator, and the non-inverting input end of the third comparator is grounded through a fifth resistor; the resistance value of the seventh resistor is 500 times that of the fourth resistor;
the voltage stabilizing values of the three voltage stabilizing tubes are all + 3.3V.
In the above scheme, the amplification gain display module comprises an SN74LS138 type 3-line-8-line decoder and four groups of light emitting diodes; pin 16 of the decoder is connected with +5V voltage, and pins 1 and 2 are used as input ends and connected with the logic coding module and the output end of the manual/automatic mode selection switch module; the pins 15, 14, 13 and 12 are low-level effective output ends and are respectively connected with the cathodes of the four groups of light-emitting diodes; the anodes of the four groups of light-emitting diodes are connected with +3.3V voltage through resistors.
In the above scheme, the voltage frequency conversion module includes an LM331 chip and an external circuit; the LM331 chip comprises a mirror current source, a current switch, a current pump, a band-gap reference circuit, an R-S trigger, an input comparator, a timing comparator, an output driving tube, an output protection tube and a reset transistor.
In the above scheme, the programmable gain operational amplification module adopts a PGA204 high-precision programmable gain instrumentation amplifier, and the gain is 1, 10, 100, or 1000.
In the scheme, the logic coding module adopts an SN74HC148 type 8-line-3-line priority coder.
In the above scheme, the power module is composed of an AC 220V-to-DC +12V module, a DC + 12V-to-DC +5V module, a DC +5V voltage reference module, a DC + 5V-to-DC ± 5V module, a DC + 5V-to-DC ± 15V module, and a DC + 5V-to-DC +3.3V module;
the AC 220V-DC +12V conversion module is composed of an ACF-10S12 AC/DC power supply module and an external circuit, and is used for converting AC220V voltage into DC +12V voltage;
the DC +12V to DC +5V conversion module consists of an MCW03-12S05 direct current/direct current converter module and an external circuit, and realizes conversion of direct current +12V voltage into direct current +5V voltage;
the DC +5V voltage reference module adopts a REF5050 voltage reference chip and outputs stable +5V reference voltage through +5V power supply;
the voltage output pins of the MCW03-12S05 and the REF5050 are connected with the voltage input pins of a module for converting DC +5V into DC +/-5V, a module for converting DC +5V into DC +/-15V and a module for converting DC +5V into DC +3.3V, and the voltage input pins provide +5V voltage input.
The DC +5V to DC +/-5V module adopts a G0505S-1WR2 direct current/direct current positive and negative double-path output power module which is externally connected with a plurality of groups of capacitors to realize the conversion of direct current +5V voltage into direct current +/-5V voltage; the DC +5V to DC +/-15V module adopts a G0515S-1WR2 direct current/direct current positive and negative double-path output power module which is externally connected with a plurality of groups of capacitors to realize the conversion of direct current +5V voltage into direct current +/-15V voltage; the module for converting DC +5V into DC +3.3V adopts an LT1763CS8-3.3 low dropout voltage stabilizer, is externally connected with a plurality of groups of capacitors and inductors, and realizes +3.3V output.
Aiming at the problems of low conversion precision and low linearity of millivolt-level micro voltage and voltage frequency, the voltage-frequency conversion circuit is redesigned, so that the identification of the input voltage magnitude, the selection of amplification gain, selective amplification and the high-precision conversion of the voltage frequency of the millivolt-level micro voltage can be realized, and the voltage-frequency conversion circuit can be applied to the remote calibration of a voltage source when the verification point is the millivolt-level micro voltage.
Compared with the prior art, the invention has the following remarkable advantages: when the input voltage is millivolt-level micro voltage, the millivolt-level voltage frequency conversion circuit provided by the invention has the advantages of high conversion precision, good linearity and high stability. Aiming at the problem that the measurement precision of the existing voltage source remote calibration system based on the GPS common-view method is low when the verification point is millivolt-level micro voltage, the millivolt-level voltage frequency conversion circuit can convert the millivolt-level voltage output by the voltage source into a pulse signal, the frequency value of the pulse signal is in direct proportion to the voltage value, time frequency comparison between two ends of a remote laboratory and a calibration site is completed through the GPS common-view technology, voltage frequency conversion is performed through the millivolt-level voltage frequency conversion circuit, and then voltage comparison between the voltage sources at the two ends is completed, and remote calibration is realized.
Drawings
Fig. 1 is a block diagram of a millivolt level voltage-to-frequency conversion circuit according to the present invention.
Fig. 2 is a circuit configuration diagram of the power module of the present invention.
Fig. 3 is a circuit configuration diagram of the manual/automatic mode selection switch module of the present invention.
Fig. 4 is a circuit diagram of the millivolt-level voltage threshold comparison module of the present invention.
Fig. 5 is a circuit configuration diagram of a logic encoding block in the present invention.
Fig. 6 is a circuit configuration diagram of the programmable gain operational amplifier module according to the present invention.
Fig. 7 is a circuit configuration diagram of the voltage frequency conversion module of the present invention.
Fig. 8 is a circuit configuration diagram of the LM331 in the present invention.
Fig. 9 is a circuit configuration diagram of an amplification gain display module according to the present invention.
Fig. 10 is an overall circuit configuration diagram of the millivolt-level voltage frequency conversion circuit of the present invention.
Detailed Description
The invention can solve the problems of low voltage frequency conversion precision and low linearity when the input voltage is millivolt-level micro voltage. By adopting the invention, when the input voltage is more than 1V, the voltage frequency conversion can be directly carried out without amplification, and when the input voltage is lower than 1V, the amplification of corresponding gains is carried out according to different magnitudes of the input voltage, and then the voltage frequency conversion is carried out, so that the accuracy of the voltage frequency conversion is ensured.
As shown in fig. 1, the millivolt-level voltage-frequency conversion circuit applied to the voltage source remote calibration system provided by the present invention includes a power module, a manual/automatic mode selection switch module, a millivolt-level voltage threshold comparison module, a logic coding module, a programmable gain operation amplification module, a voltage-frequency conversion module, and an amplification gain display module. The power module is used for providing power and reference voltage for other modules, and the power module provides +/-5V, +3.3V and +/-15V voltage for other modules through external 220V alternating voltage and a 5V battery. The manual/automatic mode selection switch module realizes the switching of two modes of manually selecting amplification gain and automatically identifying input voltage and selecting corresponding amplification gain, and can realize the selection of the amplification gain in the manual mode. The millivolt-level voltage threshold comparison module is composed of three groups of single-limit comparators, the thresholds of the three groups of single-limit comparators are respectively 1V, 100mV and 10mV, the input voltage is identified and judged in an automatic mode, the voltage is judged to be in any range of more than 1V, 100mV-1V, 10mV-100mV and less than 10mV, and then corresponding logic signals are output to the logic coding module. The logic coding module is used for providing logic signals for the programmable gain operation amplification module. The programmable gain operation amplification module realizes the amplification of 1 time, 10 times, 100 times or 1000 times of the input voltage, and the amplification gain of the programmable gain operation amplification module is determined by the logic signal provided by the logic coding module. The voltage frequency conversion module realizes high-precision voltage frequency conversion of the amplified voltage and outputs a pulse string of which the frequency is in direct proportion to the input voltage.
The specific circuit structure of each module in the present invention is described in detail below with reference to the accompanying drawings.
Fig. 2 is a circuit configuration diagram of the power module. The power module is composed of an AC 220V-to-DC +12V module, a DC + 12V-to-DC +5V module, a DC +5V voltage reference module, a DC + 5V-to-DC +/-5V module, a DC + 5V-to-DC +/-15V module and a DC + 5V-to-DC +3.3V module.
The AC220V to DC +12V conversion module is composed of an ACF-10S12 AC/DC power supply module of MINMAX company and an external circuit, and realizes conversion of AC220V voltage into DC +12V voltage. The module for converting DC +12V into DC +5V is composed of a module of a MCW03-12S05 direct current/direct current converter of MINMAX company and an external circuit, and the direct current +12V voltage is converted into direct current +5V voltage. The DC +5V voltage reference module adopts a REF5050 voltage reference chip of TI company, has the characteristics of low noise, low temperature drift and high precision, supplies power by +5V, and outputs stable +5V reference voltage. In order to adapt to various application scenes, two power supply modes of alternating current 220V and direct current +5V of the power module can be realized through the three modules, and the modules can be supplied with power through an alternating current 220V power supply or a direct current 5V battery according to field environment conditions. The voltage output pins of the MCW03-12S05 and the REF5050 are connected with the voltage input pins of a module for converting DC +5V into DC +/-5V, a module for converting DC +5V into DC +/-15V and a module for converting DC +5V into DC +3.3V, and the voltage input pins provide +5V voltage input.
The DC +5V to DC +/-5V module adopts a G0505S-1WR2 direct current/direct current positive and negative double-path output power module of MONSUN company, and is externally connected with a plurality of groups of capacitors to convert direct current +5V voltage into direct current +/-5V voltage. Pin 1 of G0505S-1WR2 is +5V voltage input terminal, pin 7 and pin 5 are + 5V-5V voltage output terminals, pin 7 and V of millivolt level voltage threshold comparison moduleccThe pin is connected to provide +5V power supply for the module; the pin 5 is connected with an external circuit consisting of a resistor and a voltage-stabilizing tube of the millivolt-level voltage threshold comparison module to form three groups of single-limit comparators and provide-5V reference voltage for the single-limit comparators; pin 7 and V of logic coding moduleccThe pin is connected and provides +5V power supply for the pin; pin 7 is also connected to pin 2 of SW1 of the manual/automatic mode selection switch module to provide a high level for the switch module.
The DC +5V to DC +/-15V module adopts a G0515S-1WR2 direct current/direct current positive and negative double-path output power module of MONSUN company, and is externally connected with a plurality of groups of capacitors to convert direct current +5V voltage into direct current +/-15V voltage. Pin 1 of G0515S-1WR2 is +5V voltage input end, pin 7, pin 5 are +15V, -15V voltage output pin respectively, pin 7, pin 5 connect with + V, -V pin of the operational amplification module of programmable gain separately, provide the +/-15V power for this module; pin 7 is connected to the VS pin of the voltage to frequency conversion module to provide +15V power to the module.
The DC +5V to DC +3.3V module selects LT1763CS8-3.3 micropower, low-noise and low-dropout voltage stabilizer of LT company, is externally connected with a plurality of groups of capacitors and inductors to realize +3.3V output, a pin 1 is a voltage output pin, and the pin 1 is connected with anodes of four groups of light-emitting diodes of the amplification gain display module to provide high level for the anodes of the light-emitting diodes.
Fig. 3 is a circuit configuration diagram of the manual/automatic mode selection switch module of the present invention. The manual/automatic mode selection switch module is composed of a double pole double throw switch SW1 and a dip switch SW 2. The amplification gain can be manually selected and the input voltage can be automatically identified and the corresponding amplification gain can be selected by switching the double-pole double-throw switch SW1, and the amplification gain can be selected in the manual mode by toggling the dial switch SW 2. The input voltage of the whole millivolt-level voltage frequency conversion circuit is input from a pin 1 of SW1, a pin 2 supplies power for +5V, and a pin 3 is connected with a voltage input pin of the millivolt-level voltage threshold comparison module through an external circuit of the millivolt-level voltage threshold comparison module to provide input voltage for three sets of single-limit comparators. Pin 6 of SW1 is connected to pins 1 and 2 of toggle switch SW2 to provide +5V high level input; pins 4, 5 of SW1 are grounded; pins 4 and 3 of SW2 are connected to pins a1 and a0 of the programmable gain operational amplifier module, respectively, and pins 4 and 3 of SW2 are connected to pin A, B of the amplification gain display module, respectively, to output logic levels to the programmable gain operational amplifier module and the amplification gain display module.
If the module is switched to a manual amplification gain selection mode, the magnitude range of the voltage value of the detection point is judged manually, and the amplification gain is selected actively. The double-pole double-throw switch SW1 is switched to enable the pins 1 and 4 to be communicated, the pins 2 and 6 to be communicated, so that the input voltage is led out from the ground wire, and the +5V high level is led into the dial switch SW2 without passing through the millivolt level voltage threshold comparison module. If the input voltage U isiIf the voltage is more than 1V, the amplification is not selected, SW2 is toggled to disconnect the pins 1 and 4 and the pins 2 and 3, and the pins 4 and 3 both output low level, namely logic '00'. If the input voltage U isiAnd the amplification is selected to be 10 times when the voltage is 100mV-1V, SW2 is toggled to open the pins 1 and 4, close the pins 2 and 3, and output low and high levels respectively at the pins 4 and 3, namely logic '01'. If the input voltage U isiThe amplification is selected to be 100 times from 10mV to 100mV, SW2 is toggled to close pins 1 and 4 and open pins 2 and 3, and pins 4 and 3 output high and low levels respectively, i.e. logic '10'. If the input voltage U isiUnder 10mV, the amplification is selected to be 1000 times, SW2 is toggled to close the pins 1 and 4 and the pins 2 and 3, and the pins 4 and 3 both output high level, i.e. logic "11".
If the module is switched to the mode of automatically identifying the input voltage, the range of the voltage value of the detection point does not need to be judged manually, and the corresponding amplification gain is automatically selected by automatically identifying the input voltage. The double-pole double-throw switch SW1 is switched to enable the pins 1 and 3 to be communicated, the pins 2 and 5 to be communicated, so that the input voltage is led into the millivolt-level voltage threshold comparison module for automatic identification, and no current passes through the dial switch SW 2.
Fig. 4 is a circuit diagram of the millivolt-level voltage threshold comparison module of the present invention. The millivolt voltage threshold comparison module is composed of an LM339LV four-way differential comparator chip of TI company and an external circuit composed of a resistor and a voltage regulator tube. The LM339LV chip consists of four independent voltage comparators,three comparators A, B, C are externally connected with resistors and voltage-stabilizing tubes with specific parameters to form three sets of single-limit comparators. The description will be given by taking the comparator A as an example: pin 4 is the inverting input of comparator A, pin 5 is its non-inverting input, pin 2 is the output, and input voltage U is appliediA reference voltage U connected to pin 4 via a resistor R2refThe resistor R1 is connected to the pin 4, the pin 2 is connected to the anode of the voltage regulator tube D1, the cathode of the voltage regulator tube D1 is connected to the pin 4, amplitude limiting is achieved, the voltage regulation value of the voltage regulator tube D1 is 3.3V, and the pin 5 is grounded through the resistor R5. According to the relevant principle, the threshold level of the one-way comparator A is
Figure BDA0003490741270000071
When the input voltage is larger than or equal to 1V, the pin 2 outputs 3.3V high level, and when the input voltage is smaller than 1V, the pin 2 outputs 0V low level. Similarly, the threshold level of the one-limit comparator B is 100mV, and it can be realized that when the input voltage is greater than or equal to 100mV, the pin 1 outputs 3.3V high level, and when the input voltage is less than 100mV, the pin 1 outputs 0V low level. The threshold level of the one-way comparator C is 10mV, so that when the input voltage is greater than or equal to 10mV, the pin 14 outputs 3.3V high level, and when the input voltage is less than 10mV, the pin 14 outputs 0V low level. Pins 2, 1 and 14 are respectively connected with pins 4, 3 and 2 of the logic coding module to input logic level for the logic coding module; the-5V reference voltage input is provided by the power module G0505S-1WR2, pin 3 is the power pin, and the module supports +5V power.
The millivolt-level voltage threshold comparison module can realize that pins 2, 1 and 14 output logic '111' when the input voltage is more than 1V; when the input voltage is within 100mV-1V, pins 2, 1, 14 output logic "011"; when the input voltage is within 10mV-100mV, pins 2, 1, 14 output logic '001'; pins 2, 1, 14 output logic "000" when the input voltage is below 10 mV.
Fig. 5 is a circuit configuration diagram of a logic encoding block in the present invention. The logic coding module selects an SN74HC148 type 8-line-3-line priority coder of TI company, has an input priority coding function, codes 8 data lines into a 3-bit binary logic signal, and has an input end and an output end which are effective under low level. The pin 16 is a power supply pin, and the module supports +5V power supply; pins 4, 3, 2 receive the logic levels from pins 2, 1, 14 of the millivolt-level voltage threshold comparison module as address inputs, and the other address terminals, i.e., pins 1, 10, 11, 12, 13, are grounded; the pin 5 of the low level effective enabling end is grounded; the output end is connected with the pins a1 and a0 of the programmable gain operational amplification module only by the pins a1 and a0, namely the pins 7 and 9, respectively, and outputs a logic level to the programmable gain operational amplification module.
The logic coding module can realize that when the pins 4, 3 and 2 input logic '111', the pins 7 and 9 output logic '00'; when pins 4, 3, 2 input logic "011", pins 7, 9 output logic "01"; when pins 4, 3, 2 input logic "001", pins 7, 9 output logic "10"; when pins 4, 3, 2 input logic "000", pins 7, 9 output logic "11".
Fig. 6 is a circuit configuration diagram of the programmable gain operational amplifier module according to the present invention. The programmable gain operational amplification module selects PGA204 high-precision programmable gain instrument amplifiers of TI company, the gains are 1, 10, 100 and 1000, the programmable gain instrument amplifiers are selected by two TTL or CMOS compatible address lines A0 and A1, and the PGA204 has extremely low offset voltage (50 muV), drift (0.25 muV/DEG C) and extremely high common mode rejection ratio (115 dB when the gain is 1000) after laser fine tuning. Pins 13 and 8 are power supply pins, supply power for +/-15V and are provided by G0515S-1WR2 of a power supply module; the pin 5 is a voltage input end, and the input voltage of the whole millivolt-level voltage-frequency conversion circuit is input by the pin 5; pins 16 and 15 are logic level input terminals a1 and a0, and in the manual amplification gain mode, the pins 16 and 15 receive the logic levels output by pins 4 and 3 of the dial switch SW2, and in the automatic identification input voltage mode, the pins 16 and 15 receive the logic levels output by pins 7 and 9 of the logic coding module; the pin 11 is a voltage output end, and the input voltage is amplified by the module and then is output by the pin 11; pin 12 is a feedback terminal and is connected to pin 11, and pins 4, 10, and 14 are grounded.
The programmable gain operation amplification module can realize that when the pins 16 and 15 input logic '00', the amplification gain of the module is 1; when the pins 16, 15 input logic "01", the gain is 10; when pin 16, 15 inputs logic "10", the gain is 100; when pin 16, 15 inputs logic "11", the gain is 1000.
Fig. 7 is a circuit configuration diagram of the voltage frequency conversion module of the present invention. The voltage frequency conversion module is composed of an LM331 chip of TI company and an external circuit composed of a specific parameter resistor capacitor with high temperature stability. When LM331 is used as the voltage frequency converter, its output is a pulse train, the frequency of the pulse train is in direct proportion relation with the voltage input, and the pulse output is compatible with all logic forms, LM331 has adopted the new temperature compensation band gap reference circuit, have very high precision in the whole working temperature range and under the low 4.0V mains voltage, LM331 temperature stability is strong, can reach 50 ppm/degree C, its dynamic range is wide at the same time, can reach 100dB, the linearity is good, the maximum nonlinear distortion is less than 0.01%.
Referring to fig. 8, fig. 8 is a circuit configuration diagram of LM331 in the present invention. LM331 mainly comprises parts such as mirror current source, current switch, current pump, band gap reference circuit, R-S flip-flop, input comparator, timing comparator, output drive tube, output protection tube and reset transistor. The band-gap reference circuit is used for providing bias current for each circuit; the current pump maintains the voltage of the pin 2 at 1.90V; the current of the pin 1 is equal to that of the pin 2 by the mirror current source; the non-inverting input end (pin 7) of the input comparator is connected with the input voltage to be converted; the output driving tube adopts a collector open circuit mode, and can change the logic level (pin 3) of output pulse according to an external power supply so as to adapt to different logic circuits such as TTL, DTL, CMOS and the like.
The pin 8 is a power supply pin, supports +15V power supply and is provided by G0515S-1WR2 of a power supply module; the pin 7 is a voltage input end and receives the output voltage of the programmable gain operational amplification module; the pin 3 is a frequency output end, which is used as an output end of the whole millivolt-level voltage-frequency conversion circuit and outputs a pulse string with a frequency in a direct proportion relation with the input voltage. Pin 1 is a current output end, pin 6 is a threshold input end, and a 47 omega resistor R9 and a1 muF capacitor C25 are connected in series to be grounded, so that the linearity of the module can be improved; the pin 5 is the input end of the R-C filter, and a low-pass filter circuit is formed by a capacitor C27 and a resistor R11; the pin 2 is a reference current input terminal, and is connected to the fixed resistor R7 and the adjustable resistor Rp which are connected in series, so as to adjust an error caused by the resistor R8, the resistor R11 and the capacitor C27.
When the pin 7 inputs a positive voltage Ui' (Positive Voltage U)iThat is, the amplified voltage output by the programmable gain operational amplifier module), the input comparator outputs a high level, so that the R-S flip-flop is set, the Q terminal outputs a high level, the output driving transistor T1 is turned on, and the pin 3 outputs a low level. Meanwhile, the mirror current source is connected to the pin 1 to charge the capacitor C25; at this time, since the reset transistor is turned off, the power source VS charges the capacitor C27 through the resistor R11; when the voltage at two ends of the capacitor C27 is higher than 2/3VS, and the voltage of the pin 6 is higher than that of the pin 7, the timing comparator outputs high level to reset the R-S trigger, the Q end outputs low level, the output driving tube is cut off, and the pin 3 outputs high level under the action of a pull-up power supply. At the same time, the reset transistor is turned on and the capacitor C27 discharges. At this point, the current switch is open to the other side, and capacitor C25 discharges through resistor R8. When the voltage across the capacitor C25 is less than or equal to the input voltage UiWhen the trigger is triggered, the input comparator outputs high level again, the R-S trigger is set, and the trigger is circularly reciprocated to form self-excitation. When the voltage at pin 5 is higher than 2/3VS, if the voltage at pin 7 is higher than that at pin 6, the flip-flop will not be reset, and the voltage at pin 6 will continue to increase until the voltage at pin 7 is lower than that at pin 6. This condition is typically used for start-up conditions or when the input signal is overloaded, the frequency output is 0. When the input signal is recovered to normal, the output frequency will work normally.
From the charge balance of the capacitor C25 during charging and discharging, it can be seen that:
Figure BDA0003490741270000091
wherein, t1The charging time of the capacitor C24 is equal to the timing period of charging the capacitor C27 by VS through R11, i.e. t1＝1.1×R11×C27，t2The discharge time of the capacitor C25. U shapeLThe voltage across R8 at the end of charging is equal to the magnitude of the non-inverting input of the input comparator, i.e., Ui'. i is from a mirror current sourceThe size of the reference voltage is determined by 1.90V of the band-gap reference circuit and external resistors R7 and Rp,
Figure BDA0003490741270000101
this gives:
Figure BDA0003490741270000102
when R8, R11, C27, R7 and Rp are fixed in size, the output frequency foAnd the voltage and frequency conversion is realized in a direct proportion relation with the input voltage Ui'.
When the voltage source calibration circuit is applied to remote calibration of a voltage source, in order to ensure the consistency of two millivolt-level voltage-frequency conversion circuits at a remote laboratory end and a calibration site end, the adjustable resistor Rp needs to be adjusted before calibration work, so that the linear relation between the output frequency and the input voltage of the two millivolt-level voltage-frequency conversion circuits is consistent.
Fig. 9 is a circuit configuration diagram of an amplification gain display module according to the present invention. The amplification gain display module is composed of an SN74LS138 type 3-line-8-line decoder and four groups of light emitting diodes of TI company. Pin 16 of the SN74LS138 decoder is the power supply pin, +5V supplies power; pins 1 and 2 are address input terminals A, B, and in the manual amplification gain mode, pins 1 and 2 receive the logic levels output by pins 4 and 3 of the dial switch SW2, and in the automatic identification input voltage mode, pins 1 and 2 receive the logic levels output by pins 7 and 9 of the logic coding module; the pin 6 is a high-level effective gating end and is connected with a +5V power supply; pins 4 and 5 are low-level effective gating ends and are grounded; the pins 15, 14, 13 and 12 are low-level effective output terminals Y0, Y1, Y2 and Y3, and are respectively connected with the cathodes of the four groups of light emitting diodes; the anodes of the four groups of light emitting diodes are connected with a +3.3V power supply through resistors, and the +3.3V power supply is provided by LT1763CS8-3.3 of the power supply module.
The amplification gain display module is used for displaying the amplification gain in real time. The amplification gain display module can realize that when the pins 1 and 2 input logic '00', the pin 15 is at low level, the pins 14, 13 and 12 are at high level, the LED1 is turned on, the lamp is on, and other LEDs are not on, which indicates that the amplification gain is 1; when the pins 1 and 2 input logic '01', the pin 14 is at low level, the LED2 is on, and the amplification gain is 10; when the logic '10' is input into the pins 1 and 2, the pin 13 is at a low level, the LED3 is on, and the amplification gain is 100; when pin 1, 2 inputs logic "11" and pin 12 is low, LED4 lights, indicating an amplification gain of 1000.
Fig. 10 is an overall circuit structure diagram of the millivolt-level voltage-frequency conversion circuit of the present invention formed by connecting the above circuit structures of the modules in fig. 2 to 9.
When the voltage source remote calibration circuit is applied to remote calibration of a voltage source, the millivolt-level voltage frequency conversion circuit provided by the invention can convert millivolt-level voltage output by the voltage source into pulse signals, the frequency value of the pulse signals is in direct proportion to the voltage value, in the existing voltage source remote calibration system, the frequency comparison of the output of the millivolt-level voltage frequency conversion circuit at two ends of a remote laboratory and a calibration site can be completed through a GPS common vision technology, the frequency is obtained by converting the voltage of a standard voltage source and the voltage of a voltage source to be calibrated through the millivolt-level voltage frequency conversion circuit, the voltage comparison of the voltage sources at two ends can be further completed, and the remote calibration is realized. When the detected points are millivolt-level tiny voltage, the input voltage is amplified through the circuit of the invention, the amplification gain is displayed in real time by the amplification gain display module, and for the detected points, the calculated voltage difference value is reduced by corresponding times during data processing to be used as a calibration result.

Claims (10)

1. A millivolt level voltage frequency conversion circuit applied to a voltage source remote calibration system is characterized by comprising a power supply module, a manual/automatic mode selection switch module, a millivolt level voltage threshold comparison module, a logic coding module, a programmable gain operation amplification module, a voltage frequency conversion module and an amplification gain display module;
the power supply module is connected with other modules and is used for providing working voltage for other modules;
the manual/automatic mode selection switch module is used for realizing the switching between a manual mode and an automatic mode; the manual mode refers to manually identifying input voltage and manually selecting corresponding amplification gain, and the automatic mode refers to automatically identifying input voltage and automatically selecting corresponding amplification gain;
the millivolt-level voltage threshold comparison module is respectively connected with the manual/automatic mode selection switch module and the logic coding module and is used for automatically identifying input voltage and outputting corresponding logic level to the logic coding module through three sets of single-limit comparators with threshold levels of 10mV, 100mV and 1V respectively when the manual/automatic mode selection switch module is switched to an automatic mode;
the logic coding module is respectively connected with the millivolt-level voltage threshold comparison module, the programmable gain operation amplification module and the amplification gain display module, and is used for coding the logic level output by the millivolt-level voltage threshold comparison module and outputting the corresponding logic level to the programmable gain operation amplification module and the amplification gain display module;
the programmable gain operational amplification module is respectively connected with the logic coding module and the manual/automatic mode selection switch module; in an automatic mode, the programmable gain operation amplification module amplifies the input voltage by corresponding times according to the logic level output by the logic coding module; in the manual mode, the programmable gain operation amplification module amplifies the input voltage by corresponding times according to the logic level output by the manual/automatic mode selection switch module;
the voltage frequency conversion module is connected with the programmable gain operational amplification module and is used for converting the voltage output by the programmable gain operational amplification module into corresponding frequency;
and the amplification gain display module is respectively connected with the logic coding module and the manual/automatic mode selection switch module and is used for displaying the amplification gain according to the logic level output by the logic coding module or the manual/automatic mode selection switch module.
2. A mv-level voltage to frequency conversion circuit for use in a voltage source remote calibration system as claimed in claim 1, wherein said manual/automatic mode selection switch module comprises a double pole double throw switch and a dip switch; the double-pole double-throw switch is provided with 6 pins, and the dial switch is provided with 4 pins; pin 1 of the double-pole double-throw switch is connected with an input voltage, pin 2 is connected with a +5V voltage, pins 4 and 5 are grounded, pin 3 is connected with the input end of the millivolt-level voltage threshold comparison module, and pin 6 is connected with pins 1 and 2 of the dial switch; pins 3 and 4 of the dial switch are used as output ends in a manual mode and are respectively connected with input ends of the programmable gain operation amplification module and the amplification gain display module; in a manual mode, pins 1 and 4 of the double-pole double-throw switch are communicated, and pins 2 and 6 are communicated; in the automatic mode, pins 1 and 3 of the double-pole double-throw switch are communicated, and pins 2 and 5 are communicated.
3. A mv-level voltage to frequency conversion circuit for a voltage source remote calibration system as claimed in claim 2, wherein in the manual mode, when the input voltage is 1V or more, the manual toggle switches to disconnect pins 1 and 4 and pins 2 and 3 of the dial switch; when the input voltage is more than or equal to 100mV and less than 1V, manually shifting to disconnect pins 1 and 4 of the dial switch and close pins 2 and 3; when the input voltage is more than or equal to 10mV and less than 100mV, pins 1 and 4 of the dial switch are closed by manual shifting, and pins 2 and 3 are opened; when the input voltage is less than 10mV, manual toggling closes pins 1 and 4 and pins 2 and 3 of the dip switch.
4. A mv-level voltage-frequency conversion circuit applied to a voltage source remote calibration system according to claim 1, wherein said mv-level voltage threshold comparison module comprises an LM339LV chip and an external circuit composed of a resistor and a voltage regulator tube; the LM339LV chip consists of four independent voltage comparators, and three comparators, an external resistor and a voltage regulator tube are utilized to form three sets of single-limit comparators;
for a first comparator with the threshold level of 1V, an input voltage is connected with the inverting input end of the first comparator through a second resistor, a 5V reference voltage is connected with the inverting input end of the first comparator through a first resistor, the output end of the first comparator is connected with the anode of a first voltage-stabilizing tube, the cathode of the first voltage-stabilizing tube is connected with the inverting input end of the first comparator, and the non-inverting input end of the first comparator is grounded through a fifth resistor; the first resistance value is 5 times of the second resistance value;
for a second comparator with the threshold level of 100mV, an input voltage is connected with the inverting input end of the second comparator through a third resistor, a 5V reference voltage is connected with the inverting input end of the second comparator through a sixth resistor, the output end of the second comparator is connected with the anode of a second voltage-stabilizing tube, the cathode of the second voltage-stabilizing tube is connected with the inverting input end of the second comparator, and the non-inverting input end of the second comparator is grounded through a fifth resistor; the sixth resistance value is 50 times of the third resistance value;
for a third comparator with the threshold level of 10mV, the input voltage is connected with the inverting input end of the third comparator through a fourth resistor, a 5V reference voltage is connected with the inverting input end of the third comparator through a seventh resistor, the output end of the third comparator is connected with the anode of a third voltage-stabilizing tube, the cathode of the third voltage-stabilizing tube is connected with the inverting input end of the third comparator, and the non-inverting input end of the third comparator is grounded through a fifth resistor; the seventh resistor is 500 times of the fourth resistor;
the voltage stabilizing values of the three voltage stabilizing tubes are all + 3.3V.
5. A millivolt-level voltage to frequency conversion circuit applied to a voltage source remote calibration system as claimed in claim 1 wherein said amplification gain display module comprises SN74LS138 type 3-line-8 line decoder and four sets of leds; pin 16 of the decoder is connected with +5V voltage, and pins 1 and 2 are used as input ends and connected with the logic coding module and the output end of the manual/automatic mode selection switch module; the pins 15, 14, 13 and 12 are low-level effective output ends and are respectively connected with the cathodes of the four groups of light-emitting diodes; the anodes of the four groups of light-emitting diodes are connected with +3.3V voltage through resistors.
6. The millivolt-level voltage-frequency conversion circuit applied to the voltage source remote calibration system as claimed in claim 1, wherein the voltage-frequency conversion module comprises an LM331 chip and an external circuit; the LM331 chip comprises a mirror current source, a current switch, a current pump, a band-gap reference circuit, an R-S trigger, an input comparator, a timing comparator, an output driving tube, an output protection tube and a reset transistor.
7. The millivolt-level voltage-frequency conversion circuit applied to a voltage source remote calibration system as claimed in claim 1, wherein the programmable gain operational amplification module adopts a PGA204 high-precision programmable gain instrument amplifier, and the gain is 1, 10, 100, 1000.
8. A mv-level voltage to frequency converter circuit for use in a voltage source remote calibration system as claimed in claim 1 wherein said logic encoding module employs an SN74HC148 type 8-line-3-line priority encoder.
9. A millivolt-level voltage to frequency conversion circuit applied to a voltage source remote calibration system as claimed in claim 1, wherein said power module is composed of an AC220V to DC +12V module, a DC +12V to DC +5V module, a DC +5V voltage reference module, a DC +5V to DC ± 5V module, a DC +5V to DC ± 15V module, a DC +5V to DC +3.3V module;
the AC 220V-DC +12V conversion module is composed of an ACF-10S12 AC/DC power supply module and an external circuit, and is used for converting AC220V voltage into DC +12V voltage;
the DC +12V to DC +5V conversion module consists of an MCW03-12S05 direct current/direct current converter module and an external circuit, and realizes conversion of direct current +12V voltage into direct current +5V voltage;
the DC +5V voltage reference module adopts a REF5050 voltage reference chip and outputs stable +5V reference voltage through +5V power supply;
the voltage output pins of the MCW03-12S05 and the REF5050 are connected with the voltage input pins of a module for converting DC +5V into DC +/-5V, a module for converting DC +5V into DC +/-15V and a module for converting DC +5V into DC +3.3V, and the voltage input pins provide +5V voltage input.
10. The mv-level voltage-frequency conversion circuit applied to a voltage source remote calibration system according to claim 9, wherein the DC +5V to DC ± 5V module employs a G0505S-1WR2 DC/DC positive-negative dual-output power module, which is externally connected with a plurality of sets of capacitors, so as to convert the DC +5V voltage to DC ± 5V voltage; the DC +5V to DC +/-15V module adopts a G0515S-1WR2 direct current/direct current positive and negative double-circuit output power module which is externally connected with a plurality of groups of capacitors to realize the conversion of direct current +5V voltage into direct current +/-15V voltage; the module for converting DC +5V into DC +3.3V adopts an LT1763CS8-3.3 low dropout voltage stabilizer, is externally connected with a plurality of groups of capacitors and inductors, and realizes +3.3V output.
CN202210095746.XA 2022-01-26 2022-01-26 Millivolt-level voltage frequency conversion circuit applied to voltage source remote calibration system Pending CN114594416A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115328257A (en) * 2022-09-14 2022-11-11 国仪量子(合肥)技术有限公司 Multi-channel direct current system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115328257A (en) * 2022-09-14 2022-11-11 国仪量子(合肥)技术有限公司 Multi-channel direct current system

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