CN208076704U - Small signal source for examining and determine indirect access type direct current energy meter - Google Patents

Abstract

The utility model relates to the technical field of electric energy measurement and verification, which is a small-signal voltage source for verifying an indirect-connected DC electric energy meter, which includes a voltage dividing module, an analog switch, a voltage following module, and a filtering and rectifying module electrically connected in sequence and a power amplification module; the voltage divider module divides the input voltage and outputs the divided first voltage to the analog switch; the analog switch adjusts the first voltage to a second voltage by adjusting the duty cycle; the voltage follower module The second voltage is buffered to output a third voltage; the filtering and rectifying module filters the third voltage to output a fourth voltage and the like. The utility model adjusts the duty cycle by controlling the on-off time of the analog switch, realizes the continuous regulation and stable output of the DC reference voltage, and realizes the continuous and smooth output of the voltage through the voltage following module and the filtering and rectifying module. The energy meter provides a small signal voltage to ensure that the verification of the indirect connected DC electric energy meter under test is carried out accurately and normally.

Description

Small Signal Voltage Sources for Verification of Indirect Connected DC Energy Meters

technical field

The utility model relates to the technical field of electric energy measurement and verification, which is a small-signal voltage source for verifying an indirect-connected direct-current electric energy meter.

Background technique

When measuring DC current, the DC watt-hour meter is divided into two measurement methods: direct access type and indirect access type according to the size of the measurement current. The direct access type can be used when testing small currents, but it is usually used when testing large currents. Shunt indirect access type.

When the indirect access type electric energy meter is working, an external shunt will be connected. The shunt is actually a low-value resistor. The current is measured according to the volt-ampere characteristic of the resistor. When a large DC current passes through the shunt, a voltage drop will be generated and the mV level will be output. The voltage to the indirect connected energy meter. Therefore, when verifying the indirect connected electric energy meter, it is required that the verification device can output a small signal voltage of the millivolt level, and the lower limit of its adjusted output mV should generally be 1/2 of the starting current value of the tested indirect connected electric energy meter, and at the same time Considering that the possible preferred values of the shunt are low voltage values such as 30mV and 15mV, it is advisable that the lower limit of the adjusted output mV of the verification device should be less than 10μV. The biggest difficulty of the indirect-connected energy meter verification device lies in the processing of small voltage signals. Traditional small-signal voltage sources usually use resistor dividers or DA converters to convert large voltages into small-signal voltages. Here, the traditional small-signal voltage There is a voltage source that can only output at a fixed value, but cannot output continuously and smoothly.

Contents of the invention

The utility model provides a small-signal voltage source for testing an indirect-connected DC electric energy meter, which overcomes the above-mentioned deficiencies in the prior art, and can effectively solve the problem that the existing small-signal voltage source can only output a small fixed value. The signal voltage cannot continuously adjust the output small signal voltage and stabilize the output.

The technical scheme of the utility model is realized through the following measures: a small signal voltage source for testing an indirect connected DC electric energy meter, including a voltage divider module, an analog switch, a voltage follower module, a filter A rectifier module and a power amplification module; the voltage divider module divides the input voltage, and outputs the divided first voltage to the analog switch; the analog switch adjusts the first voltage by adjusting the duty cycle to output The second voltage; the voltage following module buffers the second voltage and outputs the third voltage; the filtering and rectifying module filters the third voltage and outputs the fourth voltage; the power amplification module filters the fourth voltage and outputs the fifth voltage Voltage.

Below is the further optimization or/and improvement to above-mentioned utility model technical scheme:

The above-mentioned voltage divider module may include a second resistor connected in series with the first resistor and an operational amplifier, one end of the second resistor is electrically connected to the in-phase input terminal of the operational amplifier, and the other end of the second resistor is electrically connected to the output terminal of the operational amplifier. The inverting input terminal is grounded, and the output terminal of the operational amplifier is electrically connected with the input terminal of the analog switch.

The above-mentioned voltage follower module can be a voltage follower, the output terminal of the analog switch is electrically connected to the non-inverting input terminal of the voltage follower, the reverse input terminal of the voltage follower is electrically connected to the output terminal of the voltage follower, and the output terminal of the voltage follower It is electrically connected with the input end of the filter rectification module.

The filter rectifier module may include a third resistor and a first capacitor, the output terminal of the voltage follower module is electrically connected to one end of the third resistor, and the other end of the third resistor is electrically connected to one end of the first capacitor and the input terminal of the power amplification module, respectively. connection, and the other end of the first capacitor is grounded.

The above-mentioned power amplification module can be a power amplifier, the output end of the filter rectification module is electrically connected to the non-inverting input end of the power amplifier, and the inverting input end of the power amplifier is electrically connected to the output end of the power amplifier.

The utility model has a reasonable and compact structure and is easy to use, which solves the problem that the existing small signal voltage source can only output a small signal voltage at a fixed value, and cannot continuously adjust and stably output the output small signal voltage. The on-off time adjusts the duty cycle, realizes the continuous adjustment and stable output of the DC reference voltage, and realizes the continuous and smooth output of the voltage through the voltage follower module, filter rectifier module and power amplifier module, so as to provide the indirect access type for the tested The DC watt-hour meter provides a small signal voltage to ensure that the verification of the indirect connected DC watt-hour meter under test is carried out accurately and normally.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the circuit structure of the best embodiment of the utility model.

Accompanying drawing 2 is a square wave waveform diagram generated when the analog switch in accompanying drawing 1 works.

The codes in the drawings are: 1 is the voltage divider module, 2 is the voltage follower module, 3 is the filter rectification module, 4 is the power amplification module, U ₀ is the DC voltage output by the DA converter, U ₁ is the first voltage, K ₁ is an analog switch, U ₂ is the second voltage, U ₃ is the third voltage, U ₄ is the fourth voltage, U ₅ is the fifth voltage, R ₁ is the first resistor, R ₂ is the second resistor, A ₁ is an operational amplifier, A ₂ is a voltage follower, R ₃ is the third resistor, C ₁ is the first capacitor, A ₃ is a power amplifier, T ₁ is the time when the analog switch K ₁ is closed, and T ₂ is the time when the analog switch K ₁ is off open time.

Detailed ways

The utility model is not limited by the following examples, and the specific implementation manner can be determined according to the technical scheme of the utility model and actual conditions.

Below in conjunction with embodiment and accompanying drawing, the utility model is further described:

As shown in Figures 1 and 2, the small-signal voltage source used to test the indirect connected DC energy meter includes a voltage divider module 1, an analog switch K ₁ , a voltage follower module 2, and a filter and rectifier module that are electrically connected in sequence 3 and a power amplification module 4; the voltage divider module 1 divides the input voltage, and outputs the divided first voltage U ₁ to the analog switch K ₁ ; the analog switch K ₁ adjusts the duty cycle Adjust and output the _first voltage U1 to the second voltage U2; the voltage follower module ₂ buffers the _second voltage U2 and outputs the third voltage _U3 ; the filtering and rectifying module ₃ filters the third voltage U3 Outputting the fourth voltage U ₄ ; the power amplification module 4 filters the fourth voltage U ₄ to output the fifth voltage U ₅ .

The above-mentioned analog switch K ₁ controls and adjusts the size of the duty cycle through the difference in the length of the closing and opening time, provides different input energies, and outputs a square wave voltage, which is the second voltage U ₂ , so as to realize the adjustment of the output voltage and maintain Stable and continuous voltage output; the voltage follower module 2 has the characteristics of high input impedance and low output impedance, which can buffer the _second voltage U2 output by the analog switch K1 to ensure better work _of the latter stage circuit; filter rectification The module 3 filters the input third voltage U ₃ to realize smooth output of the voltage.

As shown in accompanying drawings 1 and 2, when working, the DC voltage _U0 output by the DA converter is connected to the voltage divider module 1, and the output terminal of the power amplification module 4 is electrically connected to the tested indirect connected DC electric energy meter, If the DC voltage U ₀ output by the DA converter is 2V, the first voltage U ₁ of 200mV is output after being divided by the voltage divider module 1, and the first voltage U ₁ is input to the analog switch K ₁ , as shown in Figure 2, T ₁ Is the duration of the analog switch K ₁ closing, at this time the amplitude is high level U ₁ (the first voltage), T ₂ is the duration of the analog switch K ₁ disconnection, at this time the amplitude is low level 0V, then the duty For example, a is shown in the following formula:

The first voltage U1 is adjusted by the analog switch K1 to obtain a square wave voltage, that is, the second voltage U2. The second voltage U2 is passed through the voltage follower module 2 to obtain the third voltage U3. The third voltage U3 is filtered by the filter and rectifier module 3 to obtain the fourth voltage. The voltage U4, the average value of the fourth voltage U4 is shown in the following formula:

Here, according to formula (1), it can be seen that the fourth voltage U ₄ can realize continuous output in the range of 10 μV to 200 mV, the fourth voltage U ₄ is amplified by the power amplifier module 4 to obtain the fifth voltage U ₅ , and the fifth voltage U ₅ is connected to The inspected indirect access type DC electric energy meter shall be verified.

In general, in actual work, the DC voltage U ₀ output by the DA converter is 2V, and the output DC reference voltage after 2V is divided by the DC voltage divider module 1 is generally 200mV, so the utility model uses the analog switch The continuous output of K ₁ in the range of 10μV to 200mV can fully meet the needs of actual work.

Therefore, the utility model is simple in structure and easy to use, which solves the problem that the existing small signal voltage source can only output small signal voltage at a fixed value, and cannot continuously adjust and stabilize the output small signal voltage. By controlling the analog switch K The on-off time of ₁ adjusts the duty cycle, realizes the continuous adjustment and stable output of the DC reference voltage, and realizes the continuous and smooth output of the voltage through the voltage follower module 2, the filter rectifier module 3 and the power amplifier module 4, so as to provide the tested The indirect access DC watt-hour meter provides a small signal voltage to ensure that the verification of the indirect access DC watt-hour meter is carried out accurately and normally.

According to actual needs, further optimization or/and improvement can be made to the above-mentioned small-signal voltage source for testing the indirect connected DC electric energy meter:

As shown in Figures 1 and 2, the voltage divider module 1 includes a second resistor R ₂ connected in series with the first resistor R ₁ and an operational amplifier A ₁ , one end of the second resistor R ₂ is connected to the non-inverting input terminal of the operational amplifier A ₁ Electrically connected, the other end of the _second resistor R2 is electrically connected to the output terminal _of the operational amplifier A1, the inverting input terminal _of the operational amplifier A1 is grounded, and the output terminal _of the operational amplifier A1 is electrically connected to the input terminal _of the analog switch K1.

Here, _one end of the first resistor R1 is electrically connected to the output end of the DA converter, that is, the DC voltage _U0 output by the DA converter flows into the _first resistor R1, and the other end of the _first resistor R1 is connected to the non _- inverting input end of the operational amplifier A1 electrical connection.

As shown in Figures 1 and 2, the voltage follower module 2 is a voltage follower A ₂ , the output terminal of the analog switch K ₁ is electrically connected to the non-inverting input terminal of the voltage follower A ₂ , and the reverse direction of the voltage follower A ₂ The input terminal is electrically connected to the output terminal of the voltage follower A ₂ , and the output terminal of the voltage follower A ₂ is electrically connected to the input terminal of the filtering and rectifying module 3 .

Here, the voltage follower A ₂ is a known technology, and is mainly used to buffer the second voltage U ₂ output by the analog switch K ₁ to ensure better operation of the latter stage circuit.

As shown in accompanying drawings 1 and 2, the filter rectifier module 3 includes a third resistor R ₃ and a first capacitor C ₁ , the output terminal of the voltage follower module 2 is electrically connected to one end of the third resistor R ₃ , and the third resistor R The other end of ₃ is electrically connected to one end of the first capacitor _C1 and the input end of the power amplification module 4 respectively, and the other end of the first capacitor _C1 is grounded.

Here, the filtering and rectifying module 3 is an RC low-pass filter circuit. The RC low-pass filter circuit includes a third resistor R ₃ and a first capacitor C ₁ , which are mainly used to realize smooth output of voltage.

As shown in accompanying drawing 1, 2, described power amplifying module 4 is power amplifier A ₃ , and the output end of filter rectification module 3 is electrically connected with the in-phase input end of power amplifier A ₃ , and the reverse input end of power amplifier A ₃ is connected with _The output terminals of the power amplifier A3 are electrically connected.

Here, the power amplifier _A3 is a conventionally known technology, and is mainly used to amplify the input _fourth voltage U4.

The above technical features constitute the best embodiment of the utility model, which has strong adaptability and best implementation effect, and non-essential technical features can be increased or decreased according to actual needs to meet the needs of different situations.

Claims (9)

1. a kind of small signal source for examining and determine indirect access type direct current energy meter, it is characterised in that including being sequentially electrically connected Division module, analog switch, voltage follow module, filter rectification module and power amplifier module；The division module is to defeated The voltage entered is divided, and the first voltage after partial pressure is exported to analog switch；The analog switch is by adjusting duty Than being second voltage by first voltage adjustment output；The voltage follow module carries out Buffer output third electricity to second voltage Pressure；The filter rectification module is filtered the 4th voltage of output to tertiary voltage；The 4th voltage of the power amplifier module pair It is filtered the 5th voltage of output.

2. the small signal source according to claim 1 for examining and determine indirect access type direct current energy meter, feature exists Include second resistance and concatenated first resistor and operational amplifier in the division module, one end and the operation of second resistance are put Big device in-phase input end electrical connection, the other end of second resistance are electrically connected with operational amplifier output terminal, operational amplifier it is anti- Phase input end grounding, the output end of operational amplifier are electrically connected with the input terminal of analog switch.

3. the small signal source according to claim 1 or 2 for examining and determine indirect access type direct current energy meter, feature It is that the voltage follow module is voltage follower, the output end of analog switch and the in-phase input end of voltage follower are electrically connected It connects, the reverse input end of voltage follower is electrically connected with the output end of voltage follower, the output end of voltage follower and filtering Rectification module input terminal is electrically connected.

4. the small signal source according to claim 1 or 2 for examining and determine indirect access type direct current energy meter, feature It is that the filter rectification module includes 3rd resistor and the first capacitance, the output end of voltage follow module and the one of 3rd resistor End electrical connection, the other end of 3rd resistor are electrically connected with the input terminal of one end of the first capacitance and power amplifier module respectively, the The other end of one capacitance is grounded.

5. the small signal source according to claim 3 for examining and determine indirect access type direct current energy meter, feature exists In the filter rectification module include 3rd resistor and the first capacitance, the output end of voltage follow module and one end of 3rd resistor Electrical connection, the other end of 3rd resistor are electrically connected with the input terminal of one end of the first capacitance and power amplifier module respectively, and first The other end of capacitance is grounded.

6. the small signal source according to claim 1 or 2 for examining and determine indirect access type direct current energy meter, feature It is that the power amplifier module is power amplifier, the output end of filter rectification module and the in-phase input end of power amplifier Electrical connection, the reverse input end of power amplifier are electrically connected with the output end of power amplifier.

7. the small signal source according to claim 3 for examining and determine indirect access type direct current energy meter, feature exists It is power amplifier in the power amplifier module, the output end of filter rectification module and the in-phase input end of power amplifier are electric Connection, the reverse input end of power amplifier are electrically connected with the output end of power amplifier.

8. the small signal source according to claim 4 for examining and determine indirect access type direct current energy meter, feature exists It is power amplifier in the power amplifier module, the output end of filter rectification module and the in-phase input end of power amplifier are electric Connection, the reverse input end of power amplifier are electrically connected with the output end of power amplifier.

9. the small signal source according to claim 5 for examining and determine indirect access type direct current energy meter, feature exists It is power amplifier in the power amplifier module, the output end of filter rectification module and the in-phase input end of power amplifier are electric Connection, the reverse input end of power amplifier are electrically connected with the output end of power amplifier.