High-frequency current measuring circuit

Abstract

The utility model discloses a high-frequency current measuring circuit, and the circuit comprises a sampling circuit which receives a to-be-measured high-frequency current, converts the high-frequency current into a sampling signal, and outputs the sampling signal; the effective value conversion circuit is connected with the sampling circuit, receives the sampling signal, and performs multiplication operation on the sampling signal to output an effective value signal; the CPU is connected with the effective value conversion circuit, receives the effective value signal, processes the effective value signal into a digital signal and outputs the digital signal; and the display module is connected with the CPU and is used for receiving and displaying the digital signal. According to the utility model, an effective value conversion technology is adopted, an electronic circuit is adopted to replace a thermoelectric high-frequency ammeter, the structure is simplified, and the cost is reduced; and the measuring range is large and can reach several amperes, the precision is high, and the reading is visual.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of measurement technology, especially relates to a high frequency current measurement circuit. BACKGROUND

[0002] In prior art, the minimum output frequency of high frequency surgical equipment is 200 KHZ, according to the test requirement of high frequency surgical equipment output power, generally need to adopt thermoelectric type high frequency ammeter to measure. Although thermoelectric type high frequency ammeter is high in accuracy, but poor in overload capacity, and the meter is easy to burn in measurement, and is limited by range, frequently needs to change meter in process, and the operation is complicated, also uneconomical, and furthermore, as mechanical type ammeter, it is also difficult to be used as data acquisition in electronic and electrical equipment. SUMMARY

[0003] According to the utility model embodiment, provide a kind of high frequency current measurement circuit, include:

[0004] Sampling circuit, sampling circuit receives the high frequency current to be measured, and sampling circuit converts high frequency current into sampling signal and outputs;

[0005] Effective value conversion circuit, effective value conversion circuit is connected with sampling circuit, receives sampling signal, and carries out multiplication operation to sampling signal and outputs effective value signal;

[0006] CPU, CPU is connected with effective value conversion circuit, receives effective value signal, and CPU processes effective value signal into digital signal and outputs;

[0007] Display module, display module is connected with CPU, receives digital signal and displays.

[0008] Further, sampling circuit includes: current transformer and sampling resistance switching circuit;

[0009] The input end of current transformer receives the high frequency current to be measured, and the output end of current transformer is connected with sampling resistance switching circuit and effective value conversion circuit;

[0010] Current transformer is used to induct the high frequency current to be measured, and sampling resistance switching circuit converts the inducted high frequency current into sampling signal and outputs to effective value conversion circuit.

[0011] Further, sampling resistance switching circuit includes: first sampling resistance, second sampling resistance, third sampling resistance, first relay, second relay, third relay and first capacitor;

[0012] First sampling resistance, first relay and second relay are connected in series;

[0013] Second sampling resistance is connected in parallel on second relay;

[0014] The third sampling resistor is connected with the third relay in series;

[0015] One end of the first sampling resistor, one end of the third sampling resistor and one end of the first capacitor are connected with the first output end of the current transformer;

[0016] One end of the second relay, one end of the second sampling resistor, one end of the third relay and the other end of the first capacitor are connected with the second output end of the current transformer and are grounded.

[0017] Further, the effective value conversion circuit comprises a first multiplier, a second multiplier and a differential amplifier;

[0018] The input end of the first multiplier is connected with the sampling circuit, and the output end of the first multiplier is connected with the non-inverting input end of the differential amplifier through an integration capacitor;

[0019] The input end of the second multiplier is connected with the output end of the differential amplifier, and the output end of the second multiplier is connected with the inverting input end of the differential amplifier;

[0020] The output end of the differential amplifier is connected with the CPU.

[0021] Further, the effective value conversion circuit further comprises a transistor, the collector of the transistor is connected with an external power supply, the base of the transistor is connected with the output end of the differential amplifier, the emitter of the transistor is connected with the input end of the second multiplier and the CPU.

[0022] Further, the first multiplier and the second multiplier adopt AD834 multipliers.

[0023] Further, the differential amplifier adopts an LF353 intermediate frequency operational amplifier.

[0024] Further, the CPU adopts a C8051F350 chip.

[0025] Further, the display module is a digital tube or a liquid crystal screen.

[0026] The high-frequency current measurement circuit according to the embodiment of the utility model, adopt effective value conversion technique, adopt electronic circuit to replace thermoelectric type high-frequency ammeter, simplify the structure, reduce the cost, and the range of measurement is large, can reach several amperes, the precision is high, and the reading is intuitive.

[0027] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the subject technology claimed. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the subject technology claimed.

[0029] Figure 2 This is a schematic diagram of the overall structure of the high-frequency current measurement circuit according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the specific structure of the high-frequency current measurement circuit according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the operation of a high-frequency current measurement circuit according to an embodiment of the present invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, further illustrating the present invention.

[0033] First, combine Figures 1-4 The high-frequency current measurement circuit according to an embodiment of the present invention is used to measure high-frequency current and voltage, and has a wide range of applications.

[0034] like Figures 1-4 As shown, the high-frequency current measurement circuit of this utility model embodiment includes: a sampling circuit 1, an RMS conversion circuit 2, a CPU, and a display module 3.

[0035] Specifically, such as Figures 1-4 As shown, in this embodiment, the sampling circuit 1 receives the high-frequency current to be measured, converts the high-frequency current into a sampling signal and outputs it. The sampling circuit 1 also includes a sampling resistor switching circuit, and the sampling signal is a low-voltage high-frequency signal.

[0036] The effective value conversion circuit 2 is connected to the sampling circuit 1, receives the sampling signal, and performs a multiplication operation on the sampling signal to output the effective value signal, which is a differential voltage DC signal.

[0037] The CPU is connected to the RMS conversion circuit 2, receives the RMS signal, processes the RMS signal into a digital signal and outputs it. The CPU then performs internal A / D conversion, proportional calculation, and correction before outputting the digital signal. When the digital signal is determined to be too large or too small, the sampling resistor switching circuit in sampling circuit 1 is switched to ensure that the received RMS signal is within the ideal range. The CPU uses a C8051F350 chip, which has an internal oscillation frequency of 24.5MHz and includes a 16-bit ADC. Theoretically, its AD resolution can reach 5uV, which is sufficient to meet the accuracy requirements. Display errors caused by nonlinearity at certain sampling points and inherent circuit misalignment can be corrected using piecewise interpolation in software.

[0038] Display module 3 is connected to the CPU, receives digital signals and displays them. Display module 3 uses a digital tube or LCD screen, and the readings are intuitive.

[0039] Specifically, as shown in the figure, Figures 1-4 In the embodiment, the sampling circuit 1 comprises a current transformer T1 and a sampling resistance switching circuit.

[0040] The input end of the current transformer T1 receives the high-frequency current to be measured, and the output end of the current transformer T1 is connected to the sampling resistance switching circuit and the effective value conversion circuit 2. For high-frequency voltage, it can be converted into a current signal through a resistor first, and then input to the current transformer T1.

[0041] The sampling resistance switching circuit can switch different sampling resistance values according to the use requirements. The resistance value of the sampling resistance is preferably 4Ω, 5Ω and 28Ω. The selection of the sampling resistance is that the CPU automatically identifies and controls the corresponding relay to switch.

[0042] The current transformer T1 is used to induct the high-frequency current to be measured, and the sampling resistance switching circuit converts the inducted high-frequency current into a sampling signal and outputs it to the effective value conversion circuit 2.

[0043] Further, as shown in the figure, Figures 1-4 In the embodiment, the sampling resistance switching circuit comprises a first sampling resistance 11, a second sampling resistance 12, a third sampling resistance 13, a first relay J1, a second relay J2, a third relay J3 and a first capacitor C1. The first sampling resistance 11, the first relay J1 and the second relay J2 are connected in series. The second sampling resistance 12 is connected in parallel to the second relay J2. The third sampling resistance 13 is connected in series with the third relay J3. One end of the first sampling resistance 11, one end of the third sampling resistance 13 and one end of the first capacitor C1 are connected to the first output end of the current transformer T1. One end of the second relay J2, one end of the second sampling resistance 12, one end of the third relay J3 and the other end of the first capacitor C1 are connected to the second output end of the current transformer T1 and are grounded. By controlling the on-off of the first relay J1, the second relay J2 and the third relay J3, the resistance value switching of different sampling resistances can be realized. The sampling resistance can be composed of multiple resistances in parallel.

[0044] Specifically, as shown in the figure, Figures 1-4 In the embodiment, the effective value conversion circuit 2 comprises a first multiplier U1, a second multiplier U2 and a differential amplifier U3. The input end of the first multiplier U1 is connected to the sampling circuit 1, and the output end of the first multiplier U1 is connected to the non-inverting input end of the differential amplifier U3 through an integration capacitor C AV and the inverting input end of the differential amplifier U3. The input end of the second multiplier U2 is connected to the output end of the differential amplifier U3, and the output end of the second multiplier U2 is connected to the inverting input end of the differential amplifier U3. The output end of the differential amplifier U3 is connected to the CPU.

[0045] In this embodiment, the negative feedback circuit consists of a first multiplier U1, a second multiplier U2, and a differential amplifier U3. The first multiplier U1 and the second multiplier U2 are AD834 multipliers, and the differential amplifier U3 is an LF353 intermediate frequency operational amplifier.

[0046] In this embodiment, the input to the first multiplier U1 is the low-voltage, high-frequency sampling signal U output by the sampling circuit 1. i The output passes through the integrating capacitor C. AV When connected to the non-inverting input of differential amplifier U3, the output signal is `U`. i 2 The input of the second multiplier U2 is connected to the output of the differential amplifier U3, and its output is connected to the inverting input of the differential amplifier U3. The input signal of the second multiplier U2 is the output signal U of the differential amplifier U3. o The output signal is U o 2 The differential amplifier U3 outputs the effective value signal U. o Since the outputs of the first multiplier U1 and the second multiplier U2 are connected to the non-inverting and inverting inputs of the differential amplifier U3, respectively, then `U i 2 =U o 2 Therefore, we get: U o =√U i 2 That is, the effective value signal is the input sampled signal U. i The root mean square value is the effective value. As long as the frequency response of the multiplier (mainly the first multiplier U1) is high enough, the AD834 can reach over 500MHz, and the open-loop gain of the differential amplifier U3 is large enough (>10). 4 If the dynamic range of this circuit is wide, then the accuracy mainly comes from the misalignment of U1 to U3, which can be eliminated by additional misalignment adjustment.

[0047] Furthermore, such as Figure 3 As shown, in this embodiment, the RMS conversion circuit 2 further includes: a transistor Q1, the collector of transistor Q1 is connected to an external power supply, the base of transistor Q1 is connected to the output of differential amplifier U3, and the emitter of transistor Q1 is connected to the input of the second multiplier U2 and connected to the CPU. Since the second multiplier U2 also uses AD834 and has a low input impedance (25K), the feedback signal is taken from U... o (Output), therefore its load is relatively heavy, so a transistor Q1 is added to increase the output current and improve accuracy.

[0048] like Figure 3As shown, R5, R6, R7 and R8 are voltage dividing resistors, R9, R10 are balancing resistors, R11 is a power down resistor, R12, R13 are load resistors, the outputs of the first multiplier U1 and the second multiplier U2 are converted into voltage (difference) through the load resistors R12 and R13, and the integral capacitor C AV is C9.

[0049] The above, with reference to Figures 1-4 The high-frequency current measuring circuit according to the embodiments of the present application is described, effective value conversion technology is adopted, an electronic circuit is used to replace a thermal electric high-frequency ammeter, the structure is simplified, and the cost is reduced; and the range is large, can reach several amperes, the precision is high, and reading is intuitive.

[0050] It should be noted that in the present specification, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article or device. Without more limitations, the elements defined by the statement "comprising" do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0051] Although the content of the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application. After reading the above content, various modifications and alternatives of the present application will be obvious to those skilled in the art. Therefore, the protection scope of the present application should be defined by the appended claims.

Claims

1. A high frequency current measurement circuit, characterized by, The utility model relates to a high-frequency current sampling circuit, comprising: A sampling circuit receives high-frequency current to be measured, converts the high-frequency current into a sampling signal and outputs; An effective value conversion circuit is connected with the sampling circuit, receives the sampling signal, and outputs an effective value signal after multiplying operation; A CPU is connected with the effective value conversion circuit, receives the effective value signal, processes the effective value signal into a digital signal and outputs; A display module is connected with the CPU, receives the digital signal and displays.

2. The high frequency current measurement circuit of claim 1, wherein, The sampling circuit comprises a current transformer and a sampling resistance switching circuit; The input end of the current transformer receives high-frequency current to be measured, and the output end of the current transformer is connected with the sampling resistance switching circuit and the effective value conversion circuit; The current transformer is used for inducting high-frequency current to be measured, and the sampling resistance switching circuit converts the inducted high-frequency current into a sampling signal and outputs to the effective value conversion circuit.

3. The high frequency current measurement circuit of claim 2, wherein, The sampling resistance switching circuit comprises a first sampling resistance, a second sampling resistance, a third sampling resistance, a first relay, a second relay, a third relay and a first capacitor; The first sampling resistance, the first relay and the second relay are connected in series; The second sampling resistance is connected in parallel with the second relay; The third sampling resistance is connected with the third relay in series; One end of the first sampling resistance, one end of the third sampling resistance and one end of the first capacitor are connected with the first output end of the current transformer; One end of the second relay, one end of the second sampling resistance, one end of the third relay and the other end of the first capacitor are connected with the second output end of the current transformer and grounded.

4. The high frequency current measurement circuit of claim 1, wherein, The effective value conversion circuit comprises a first multiplier, a second multiplier and a differential amplifier; The input end of the first multiplier is connected with the sampling circuit, and the output end of the first multiplier is connected with the non-inverting input end of the differential amplifier through an integration capacitor; The input end of the second multiplier is connected with the output end of the differential amplifier, and the output end of the second multiplier is connected with the inverting input end of the differential amplifier; The output end of the differential amplifier is connected with the CPU.

5. The high frequency current measurement circuit of claim 4, wherein, The effective value conversion circuit further comprises a transistor, the collector of the transistor is connected with an external power supply, the base of the transistor is connected with the output end of the differential amplifier, the emitter of the transistor is connected with the input end of the second multiplier and the CPU.

6. The high frequency current measurement circuit of claim 4, wherein, The first multiplier and the second multiplier adopt AD834 multipliers.

7. The high frequency current measurement circuit of claim 4, wherein, The differential amplifier adopts an LF353 intermediate frequency operational amplifier.

8. The high frequency current measurement circuit of claim 1, wherein, The CPU adopts a C8051F350 chip.

9. The high frequency current measurement circuit of claim 1, wherein, The display module is a digital tube or a liquid crystal screen.

Images