The preamplifying circuit that is used for a kind of MOA current in resistance property detection system
Technical field
The present invention relates to a kind of amplifying circuit, relate in particular to the preamplifying circuit that is used for a kind of MOA current in resistance property detection system.
Background technology
Traditional Zinc-Oxide Arrester detection system is introduced required voltage signal and current signal in the same equipment; Voltage signal is that the secondary side of the capacitance type potential transformer (CVT) from transformer station takes out; Current signal can take out through current transformer from the ground wire of Zinc-Oxide Arrester (MOA); The perhaps lightning stroke counter through the Zinc-Oxide Arrester lower end is clipped in the two ends of lightning stroke counter with current clamp, gets method of current through small resistor resistive total current is taken out.So just need be in whole measuring process in the secondary side wiring of CVT.In order to save the CVT secondary side wiring in the measuring process, the applicant in submitting on the same day of the application the patented claim of " a kind of MOA current in resistance property detection system " by name, like Fig. 1.Second amplifying circuit 22 among Fig. 1 can be selected various ways for use; But in the model of selecting second microprocessor 21 for use; The A/D that some model carries (mould/number) converter can't be handled the negative level signal; Therefore designing what kind of second amplifying circuit 22 overcomes this situation, becomes the problem that needs solve.
Summary of the invention
The preamplifying circuit that the objective of the invention is to overcome the defective of prior art and be provided for a kind of MOA current in resistance property detection system; It carries out current-voltage conversion and preliminary the amplification with the MOA full current signal of gathering, and will pass through that current-voltage is changed and amplification after full current signal lift and be positive level.
The technical scheme that realizes above-mentioned purpose is:
The preamplifying circuit that is used for a kind of MOA current in resistance property detection system; Said MOA current in resistance property detection system comprises CVT monitor cartridge and MOA monitor cartridge; Said CVT monitor cartridge comprises first holding circuit; First microprocessor; First amplifying circuit; The one GPS module; First wireless communication module and a Flash storer; Said MOA monitor cartridge comprises second holding circuit; Second microprocessor; Second amplifying circuit; The 2nd GPS module; Second wireless communication module; The 2nd Flash storer; Keyboard and display screen
Said second amplifying circuit comprises said preamplifying circuit, and this preamplifying circuit receives the full current signal of MOA,
Said preamplifying circuit comprises resistance R 23, connects resistance R 17 and resistance R 26, instrument amplifier and the voltage follower at resistance R 23 two ends respectively, wherein:
Resistance R 23 converts said full current signal into voltage signal;
Resistance R 17 ground connection and parallelly connected with capacitor C 27; Resistance R 26 ground connection and parallelly connected with capacitor C 28;
Two input ends of said instrument amplifier connect the two ends of resistance R 23, receive the level signal at the two ends of this resistance R 23, and said instrument amplifier also receives one and lifts voltage level, will pass through the current-voltage conversion and amplify after full current signal lift and be positive level;
Said voltage follower connects the output terminal of said instrument amplifier.
The above-mentioned preamplifying circuit that is used for a kind of MOA current in resistance property detection system; Wherein, Said voltage follower comprises amplifier and resistance R 21; The in-phase input end of said amplifier is through the output terminal of the said instrument amplifier of resistance R 21 connections, and this amplifier's inverting input connects its output terminal.
The above-mentioned preamplifying circuit that is used for a kind of MOA current in resistance property detection system, wherein, said preamplifying circuit also comprises diac D5, diac D4 and diac D6, wherein:
Diac D5 connects two input ends of said instrument amplifier;
Diac D4 connects the in-phase input end and the ground connection of said instrument amplifier;
Diac D6 connects the inverting input and the ground connection of said instrument amplifier.
The above-mentioned preamplifying circuit that is used for a kind of MOA current in resistance property detection system, wherein, said resistance R 23 is the resistance that 1% precision, 50ppm temperature are floated.
The invention has the beneficial effects as follows: the present invention carries out current-voltage conversion and preliminary the amplification with the MOA full current signal of gathering; And will pass through current-voltage conversion and amplify after full current signal lift and be positive level, in order to avoid A/D (mould/number) converter that the model that second microprocessor is selected for use in " a kind of MOA current in resistance property detection system " carries can't be handled the negative level signal.Simultaneously, the present invention is simple, and it is good to be easy to time and expansion, can further connect amplification regulating circuit, makes amplification multiple more accurate.
Description of drawings
Fig. 1 is the structural representation of MOA current in resistance property detection system;
Fig. 2 is the circuit diagram that is used for a kind of preamplifying circuit of MOA current in resistance property detection system of the present invention.
Embodiment
To combine accompanying drawing that the present invention is described further below.
See also Fig. 1, the MOA monitor cartridge 2 that MOA current in resistance property detection system comprises the CVT monitor cartridge 1 that connects CVT and is connected the lightning stroke counter two ends that the MOA lower end is connected in series, CVT monitor cartridge 1 and 2 wireless connections of MOA monitor cartridge, wherein:
CVT monitor cartridge 1 comprises first microprocessor 11; And first amplifying circuit 12 that is connected respectively with this first microprocessor 11, a GPS module 13, first wireless communication module 14 and a Flash storer 15; And first holding circuit 16 that connects first amplifying circuit 12, this first holding circuit 16 connects the secondary output terminal of CVT.
MOA monitor cartridge 2 comprises second microprocessor 21; And second amplifying circuit 22 that is connected respectively with this second microprocessor 21, the 2nd GPS module 23, second wireless communication module 24, the 2nd Flash storer 25, keyboard 26 and display screen 27; And second holding circuit 28 that connects second amplifying circuit 22, this second holding circuit 28 connects the two ends of lightning stroke counter.
See also Fig. 2, the preamplifying circuit that is used for a kind of MOA current in resistance property detection system of the present invention, second amplifying circuit 22 comprises this preamplifying circuit, this preamplifying circuit receives the full current signal of MOA,
Said preamplifying circuit comprises resistance R 23, connects resistance R 17 and resistance R 26, instrument amplifier U11 and the voltage follower 100 at resistance R 23 two ends respectively, wherein:
Resistance R 23 converts said full current signal into voltage signal, and resistance R 23 is the precision resister that 1% precision, 50ppm temperature are floated, and prevents because the change in the dispersed or work of resistance directly has influence on the circuital measuring accuracy of MOA;
Resistance R 17 ground connection and parallelly connected with capacitor C 27; Resistance R 26 ground connection and parallelly connected with capacitor C 28; The loop of resistance R 17 and capacitor C 27 compositions, and the loop of resistance R 26 and capacitor C 28 compositions provide one to ground circuit for the voltage at resistance R 23 two ends, make voltage signal become current signal, are not subject to disturb, and signal is more stable;
Two input ends of instrument amplifier U11 connect the two ends of resistance R 23; Receive the level signal at the two ends of this resistance R 23; The Vcom pin of instrument amplifier U11 also receives one and lifts voltage level, thus will pass through current-voltage conversion and amplify after full current signal lift and be positive level;
Voltage follower 100 connects the output terminal of instrument amplifier U11, thereby plays the effect of impedance matching.
Specifically; Voltage follower 100 comprises amplifier U12 and resistance R 21; The in-phase input end of amplifier U12 is through the output terminal of resistance R 21 connection instrument amplifier U11, and the inverting input of this amplifier U12 connects its output terminal, and the output signal can further amplify or directly use.
In the present embodiment, said preamplifying circuit also comprises diac D5, diac D4 and diac D6, is used for suppressing transient overvoltage, wherein:
Diac D5 connects two input ends of instrument amplifier U11;
Diac D4 connects in-phase input end and the ground connection of instrument amplifier U11;
Diac D6 connects inverting input and the ground connection of instrument amplifier U11.
In the present embodiment, the model that instrument amplifier U11 selects for use is AD621; The model that amplifier U12 selects for use is LMV321.
Above embodiment only supplies to explain the present invention's usefulness; But not limitation of the present invention; The technician in relevant technologies field under the situation that does not break away from the spirit and scope of the present invention, can also make various conversion or modification; Therefore all technical schemes that are equal to also should belong to category of the present invention, should be limited each claim.