CN113884745A - Alternating current signal effective value and frequency conversion device - Google Patents
Alternating current signal effective value and frequency conversion device Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/02—Measuring effective values, i.e. root-mean-square values
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
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Abstract
The invention discloses an alternating current signal effective value and frequency conversion device which comprises a voltage sensor, a voltage acquisition circuit, a frequency acquisition circuit and a processing unit, wherein the voltage acquisition circuit comprises a root mean square-direct current converter and an AD converter, and the output end of the root mean square-direct current converter is connected with the input end of the AD converter; the input alternating current signal is converted into a direct current signal by a root mean square-direct current converter and then output, the magnitude of the direct current output is equal to the root mean square value of alternating current or fluctuating direct current input, the direct current signal can be collected by an AD converter, and the direct current signal is the effective value of the input alternating current signal. The voltage sensor, the comparator, the counter and the auxiliary circuit are used for completing the collection of the alternating current frequency, and the collection of different frequencies can be realized by configuring the A, B, C, D, E pin value of the frequency divider in the frequency collection circuit.
Description
Technical Field
The invention belongs to the technical field of test equipment, and particularly relates to an alternating current signal effective value and frequency conversion device.
Background
Alternating current signal acquisition is widely applied to various aspects in the industrial technical field, and the alternating current signal is often required to be tested in test equipment to obtain the voltage and the frequency of the alternating current signal, so that the working state of the tested equipment is judged. If a multimeter or frequency meter is embedded in the product, the volume cannot meet the requirement, and the cost is high. And a specific multimeter or frequency meter can only measure the voltage or the frequency of a certain path of electric signals, so that the universality is poor. In addition, if multi-channel signals need to be acquired simultaneously, a multimeter and a frequency meter are complex in wiring, acquired original data cannot be processed, and effective values and frequencies can be obtained only through manual calculation.
Disclosure of Invention
The invention provides an alternating current signal effective value and frequency conversion device which can be conveniently embedded into equipment with requirements and can be used for collecting the voltage and the frequency of a high-voltage alternating current signal.
In order to achieve the above object, the present invention provides an ac signal effective value and frequency conversion device, which comprises a voltage sensor, a voltage acquisition circuit, a frequency acquisition circuit and a processing unit, wherein the voltage acquisition circuit comprises a root mean square-dc converter and an AD converter, an input of the root mean square-dc converter is connected to an output end of the voltage sensor, and an output end of the root mean square-dc converter is connected to an input end of the AD converter; the frequency acquisition circuit comprises a comparator, a counter, a frequency divider and a bus buffer, wherein the input end of the comparator is connected with the output end of the voltage sensor, the output end of the comparator is connected with the input end of the counter, the output end of the counter is connected with the bus buffer, and the output end of the frequency divider is connected with the input end of the counter; the output ends of the AD converter and the bus buffer are connected with the input end of the processing unit.
Furthermore, a square wave signal output by the frequency divider is used as the threshold input of the counter, an input pin of the comparator is connected with the output of the voltage sensor, a periodic square wave signal output by the frequency divider is used as one input of the AND gate, the output end of the comparator is connected with the other input end of the AND gate, and the output end of the AND gate is connected with an input pulse pin of the counter; the counter counts in the threshold level meeting the requirement, and the output of the counter is stored in a bus buffer by the edge signal of the threshold voltage for the processing unit to read; the output of the frequency divider is connected to an interrupt of the processing unit for informing the processing unit of the point in time at which the data is read.
Further, the rms-dc converter uses a chip model AD 637.
Further, a regulating capacitor Cav1 for setting an average time constant is connected between the out pin and the Cav pin of the rms-dc converter chip.
Further, the voltage sensor output is isolated from the input.
Further, the comparator is a zero-crossing comparator.
Further, the input end of the frequency divider is connected with a crystal oscillator.
Further, the output of the frequency divider is set through pins A, B, C, D and E of the input end, and the values of the pins A, B, C, D and E are configured by the processing unit.
Compared with the prior art, the invention has at least the following beneficial technical effects:
the device of the invention converts the input alternating current signal into the direct current signal by the root mean square-direct current converter for output, the magnitude of the direct current output is equal to the root mean square value of the alternating current or the fluctuating direct current input, and the direct current signal can be collected by the AD converter, and the direct current signal is the effective value of the input alternating current signal. The voltage sensor, the comparator, the counter and the auxiliary circuit are used for completing the collection of the alternating current frequency, and the collection of different frequencies can be realized by configuring the A, B, C, D, E pin value of the frequency divider in the frequency collection circuit.
Furthermore, the adopted devices and chips are common chips, so that the purchase is convenient, the cost is low, the effective value acquisition can be realized in the balance of precision and speed through a configuration circuit, the higher sampling rate or the higher precision can be selected according to the actual requirement, and the use is convenient. The conversion device can acquire and update the effective value and the frequency of the alternating current signal in real time and can be embedded into a product.
Furthermore, the device can be used as a standard circuit to realize effective value and frequency acquisition of multi-path alternating current in a superposition mode. The principle is simple, can be realized, and can be integrated in test equipment needing to collect alternating current voltage and frequency.
Furthermore, the output and the input of the voltage sensor are isolated, the alternating current input signal can be isolated from the acquisition and conversion device, and the safety of the acquisition and conversion device is improved.
Drawings
FIG. 1 is a block diagram of the circuit configuration of the present invention;
FIG. 2 is a schematic circuit diagram of an embodiment of the voltage sensor and RMS-DC converter of the present invention;
fig. 3 is a schematic circuit diagram of an embodiment of ac frequency acquisition according to the present invention.
Detailed Description
In order to make the objects and technical solutions of the present invention clearer and easier to understand. The present invention will be described in further detail with reference to the following drawings and examples, wherein the specific examples are provided for illustrative purposes only and are not intended to limit the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1, an ac signal effective value and frequency conversion apparatus is composed of a voltage sensor, a voltage acquisition circuit, a frequency acquisition circuit, and a processing unit. The voltage acquisition circuit consists of a root mean square-direct current converter and an AD converter, the output end of the root mean square-direct current converter is connected with the input end of the AD converter, and the frequency acquisition circuit consists of a comparator, a counter, a crystal oscillator, a frequency divider, an AND gate and a bus buffer.
The measured signal is input to a voltage sensor, and the output of the voltage sensor is connected to a voltage acquisition circuit and a frequency acquisition circuit. The output of the voltage acquisition circuit and the output of the frequency acquisition circuit are both connected with the processing unit. The voltage sensor and the voltage acquisition circuit finish the effective value acquisition of the alternating current signal, and the voltage sensor and the frequency acquisition circuit finish the frequency acquisition of the alternating current signal.
The output and the input of the voltage sensor are isolated, and the alternating current input signal can be isolated from the acquisition and conversion device, so that the safety of the acquisition and conversion device is improved. Meanwhile, the voltage sensor conditions the input alternating current signal to a range which can be received by the voltage acquisition circuit and the frequency acquisition circuit.
As shown in fig. 2, the circuit includes a voltage sensor and an rms-dc converter. The circuit of the voltage sensor portion includes an input matching resistor R1 and an output sampling resistor R2. The voltage sensor is HNV-025A, and in the example of HNV-025A, the input matching resistance is selected according to the principle that the input current does not exceed 14 mA. The selection of the output sampling resistor is referenced to the input voltage range of the rms-dc converter. The turn ratio of the input and output coils of the voltage sensor is 2500: 1000 according to voltage sensor input and outputThe winding ratio of the output coil can calculate the relation U between the input voltage and the output voltageO＝UI*2.5*(RO/RI) The relation between the input current and the output current is IO＝2.5IIWherein, UOTo output a voltage value, UIIs an input voltage value, ROIs the resistance value of the input resistor, RIIs the resistance value of the output resistor, IOTo output current, IIIs the input current. In this embodiment, taking an input 380VAC ac signal as an example, the input resistor has a selected resistance of 30k, and has an input terminal with a current of about 12.7mA and an output terminal with a current of about 31.7 mA. The type of the RMS-DC converter is AD637, the resistance value selected by the output sampling resistor R3 is 200 ohms, the output voltage is about 6.3V, and the input voltage range of the AD637 is met. And selecting an input matching resistor and an output sampling resistor according to the principle for other different alternating current voltage inputs.
In fig. 2, the average time constant can be set by adjusting the capacitance value of the capacitor CAV1, and the smaller the value of the capacitor CAV1, the smaller the setup time, but the larger the error; the larger the value of CAV1, the smaller the measurement error, but the setup time will increase, and the appropriate capacitance values are selected to balance the setup time and the measurement error on different occasions. If the CAV1 capacity is selected to be 4 muF, the measurement error is 0.1% when the input signal is 10Hz, and 1% when the input signal is 3 Hz.
The RMS-DC converter provides a DC output having a magnitude equal to the RMS value of the AC or fluctuating DC input, and converts the input AC signal into a DC signal output, which is the effective value of the input AC signal. The effective value of the alternating current signal output by the RMS-DC converter can be collected by the AD converter. According to the relation between the output voltage and the input voltage of the voltage sensor, the effective value of the input alternating voltage can be calculated according to the voltage value.
The frequency acquisition circuit shown in fig. 3 includes a comparator, a counter, a crystal oscillator, a frequency divider, a bus buffer and a gate circuit. The comparator is LM319, the counter is CD40 4040BF, and the frequency divider is SN74LS 294. The input end of the bus buffer is connected with the output end of the counter, and the output end of the bus buffer is connected with the processing unit and used for storing the output data of the counter.
The comparator is designed as a zero-crossing comparator, the threshold voltage is 0V, the conditioned alternating current signal output by the voltage sensor is input to the positive end of the comparator, the ground is input to the negative end of the comparator, and the sinusoidal alternating current signal output by the voltage sensor is shaped into a square wave signal by the comparator.
One input end of the OR gate is a chip selection signal of the external data bus of the processing unit, the other input end of the OR gate is a read-write signal of the external data bus of the processing unit, the output end of the OR gate is connected with a reset pin of the counter, and the processing unit can realize the reset operation of the counter through the write operation of the external data bus.
The output of the counter is connected to the input of the bus buffer, the output of which is connected to the external data bus of the processing unit. The processing unit reads the data output by the counter through the external data bus and resets the counter. Before each operation, the counter is reset to ensure the initial value of the counter to be zero.
The crystal oscillator and the frequency divider form a frequency dividing circuit, in the frequency dividing circuit, the input of the frequency divider SN74LS294 is connected with the output pin of the crystal oscillator, the output frequency of the selected crystal oscillator is f-1 MHz, the output of the frequency dividing circuit SN74LS294 can be set through the input end A, B, C, D, E pin, and the period of the specific output signal is
f is the input to the divider and X is the value of A, B, C, D, E. The value of A, B, C, D, E in this example is controlled by GPIO of the processing unit, and different combinations of 1-31 can be realized.
The input pin of the comparator is connected with the output of the voltage sensor, and the output pin of the comparator is connected with the AND gate. The frequency dividing circuit provides a periodic square wave signal as a threshold input of the counter, and the specific implementation is as follows: the periodic square wave signal output by the frequency dividing circuit is used as one input end of an AND gate, the output of the comparator is used as the other input end of the AND gate, and the output of the AND gate is connected with an input pulse pin of the counter. The counter counts in the threshold level meeting the requirement, and the output of the counter is stored in a bus buffer by the edge signal of the threshold voltage for the processing unit to read; and meanwhile, the output of the frequency division circuit is connected with the interrupt of the processing unit, and the processing unit is informed of the time point of reading data.
The frequency of the alternating current can be calculated according to the period of the threshold level and the value of the counter. The period of the threshold level is an update period of the alternating current frequency. The period of the threshold level is T, the count value of the counter in the threshold level is N, and the frequency of the alternating current is 2N/T.
The output period of the frequency dividing circuit is related to the frequency and the precision of the measuring signal. The longer the period, the higher the measurement accuracy, the slower the update period. In actual selection, if the required precision is higher, 100 times of the measured signal period is selected, and the precision can reach 1%. In this example, the frequency of the ac power is 50Hz, i.e. the period is 20ms, and the period of the selectable threshold level is about 2s, then A, B, C, D, E of the frequency dividing circuit should be configured to be 21, and the period of the threshold level is 2.1 s. The frequency of the alternating current can be calculated according to the formula. The output period of the frequency dividing circuit for measuring other frequency signals can be selected according to the recommended principle.
The processing unit is used for: collecting data of an AD converter, and converting the data into an effective value of an AC signal; collecting a count value output by a counter, and calculating the frequency of the alternating current signal according to a threshold period; receiving an interrupt signal of a frequency dividing circuit; the value of A, B, C, D, E in the frequency divider is controlled by the GPIO.
The invention provides an alternating current signal effective value and frequency acquisition device, which consists of a voltage sensor, a root mean square-direct current converter, a comparator, a counter and an auxiliary circuit, has the advantages of simple design method, low cost, easy integration of the circuit, wide adaptability and convenient popularization, can be conveniently embedded into equipment with requirements, and is suitable for acquisition of voltages and frequencies of alternating current signals with different voltages and different frequencies, such as line voltage, phase voltage and frequency of 380V/50Hz three-phase power for industry, voltage and frequency of 220V/50Hz single-phase power for industry, line voltage, phase voltage and frequency of 208V/400Hz three-phase power for aviation and voltage and frequency acquisition and conversion of other alternating current signals.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (8)
1. An alternating current signal effective value and frequency conversion device is characterized by comprising a voltage sensor, a voltage acquisition circuit, a frequency acquisition circuit and a processing unit, wherein the voltage acquisition circuit comprises a root mean square-direct current converter and an AD converter;
the frequency acquisition circuit comprises a comparator, a counter, a frequency divider and a bus buffer, wherein the input end of the comparator is connected with the output end of the voltage sensor, the output end of the comparator is connected with the input end of the counter, the output end of the counter is connected with the bus buffer, and the output end of the frequency divider is connected with the input end of the counter;
and the output ends of the AD converter and the bus buffer are connected with the input end of the processing unit.
2. An apparatus for ac signal conversion between an effective value and a frequency according to claim 1, wherein the square wave signal outputted from the frequency divider is used as the threshold input of the counter, the input pin of the comparator is connected to the output of the voltage sensor, the periodic square wave signal outputted from the frequency divider is used as one input of the and gate, the output of the comparator is connected to the other input of the and gate, and the output of the and gate is connected to the input pulse pin of the counter; the counter counts in the threshold level meeting the requirement, and the output of the counter is stored in a bus buffer by the edge signal of the threshold voltage for the processing unit to read; the output of the frequency divider is connected to the interrupt of the processing unit for informing the processing unit of the point in time for reading data.
3. The apparatus of claim 1, wherein the rms-dc converter is AD 637.
4. An apparatus for ac signal rms-frequency conversion according to claim 3, wherein a regulating capacitor Cav1 is connected between the out pin and the Cav pin of the rms-dc converter chip for setting the average time constant.
5. An apparatus according to claim 1, wherein the voltage sensor output is isolated from the input.
6. An apparatus according to claim 1, wherein the comparator is a zero-crossing comparator.
7. An apparatus according to claim 1, wherein a crystal oscillator is connected to an input terminal of the frequency divider.
8. An apparatus according to claim 1, wherein the output of the frequency divider is set by pins a, B, C, D and E, and the values of pins a, B, C, D and E are configured by the processing unit.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116027214A (en) * | 2023-03-30 | 2023-04-28 | 湖北蓝博新能源设备股份有限公司 | Battery detection equipment and system |
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