JP2011220871A - Measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp how large a physical quantity of an object to be measured is in a short period of time.SOLUTION: There are provided a measuring unit for measuring a value of a current flowing on a power supply line 100 on the basis of a voltage data Dv that is a digital signal resulting from analog-to-digital conversion of an AC voltage Va of an input analog signal; a control unit 7 for performing first display processing, causing a display unit 5 to display a current value measured by the measuring unit; and a comparator unit 4 for comparing the value of the AC voltage Va with a predetermined reference voltage Vref to output a comparison result. The control unit 7 executes second display processing to cause the display unit 5 to display the comparison result output from the comparator unit 4.

Description

  The present invention relates to a measuring apparatus that measures and displays a physical quantity of a measurement object.

  As this type of measuring apparatus, a peak value measuring apparatus disclosed by the applicant in Japanese Patent Laid-Open No. 2001-56349 is known. This peak value measuring apparatus includes an input unit, a range amplifier, a half-wave rectifier circuit, a waveform inversion circuit, a peak value hold circuit, an A / D converter, a control means, and a display, and a peak of current flowing through the measurement object. It is configured to be able to measure values. In this peak value measuring apparatus, an AC signal to be measured from a detector such as a clamp sensor is input to an input unit, and a range amplifier amplifies the AC signal to be measured. Next, the half-wave rectification circuit half-wave rectifies the AC signal to be measured amplified by the range amplifier, and the waveform inversion circuit inverts the half-wave rectification waveform on the negative side to the positive side. Subsequently, the peak value hold circuit holds the peak value of the rectified AC signal to be measured, and the A / D converter converts the peak value into a digital signal and outputs it. Next, the control means displays the peak value of the AC signal to be measured on the display based on the digital signal.

JP 2001-56349 A (page 3-4, FIG. 1-2)

  However, this type of measuring device including the above-described peak value measuring device has the following problems to be improved. That is, in this type of measuring device, the A / D converter converts an analog signal into a digital signal, and based on the digital signal, the current value of the current flowing through the measurement object (in the above-described peak value measuring device, the peak value). Value) is displayed on the display. In this case, conversion from an analog signal to a digital signal by the A / D converter generally requires a time of 200 msec or more. In addition, this type of measuring device has an auto range function that automatically switches the measurement range of the range amplifier to the measurement range suitable for the magnitude of the signal to be measured, and the range can be switched several times before the current value is measured. The conversion process is performed by the A / D converter for the number of measurement ranges. For this reason, in this type of measuring apparatus, it takes about 200 msec to 1 sec from the start of measurement until the current value is displayed on the display unit. On the other hand, when an electric device is connected to a power supply line (for example, a commercial power source) as a measurement object, when measuring a current flowing through the power supply line, for example, a short circuit or the like inside the electric device When a failure occurs, an excessive current flows in the power supply line. In this case, since the operation time of the breaker is generally about 100 msec, which is shorter than the time of about 200 msec to 1 sec required for the measurement apparatus to display the current value, in such a situation, the power supply line It is impossible to measure and display the current flowing through the current. However, even in such a situation, there is a demand for grasping how much current is flowing in the power supply line, and development of means capable of responding to such demand is desired.

  The present invention has been made in view of such a problem to be improved, and it is a main object of the present invention to provide a measuring apparatus that can grasp in a short time how much a physical quantity of a measurement object is.

  In order to achieve the above object, the measuring apparatus according to claim 1 is configured to measure a physical quantity of a measurement object based on a digital signal obtained by analog-digital conversion of an input analog signal, and the measurement unit measures the physical quantity. A measuring device comprising a control unit for executing a first display process for displaying a physical quantity on a display unit, and comparing the analog signal value with a predetermined comparison value and outputting a comparison result The control unit executes a second display process for displaying the comparison result output from the comparison unit on the display unit.

  A measuring apparatus according to a second aspect is configured such that the comparison value can be arbitrarily set in the measuring apparatus according to the first aspect.

  The measurement apparatus according to claim 1, further comprising a comparison unit that compares the analog signal value with a predetermined comparison value and outputs a comparison result, and the control unit displays the comparison result output from the comparison unit. The second display process to be displayed is executed. In this case, the comparison unit outputs the comparison result without performing a conversion process for converting the analog signal into a digital signal. For this reason, for example, when measuring the current value of the current flowing in the power supply line as the measurement object, the comparison process for outputting the comparison result is executed in a time shorter than the time for operating the breaker connected to the power supply line. be able to. Therefore, according to this measuring apparatus, for example, when an electrical device in which a failure such as a short circuit has occurred in an electric circuit is connected to a power supply line as a measurement target, it flows into the power supply line before the breaker is activated. As a result of being able to display in a short time whether or not the current value of the current is equal to or greater than the comparison value, how much current is flowing in the power line (how much is the physical quantity of the measurement object) The user can be surely grasped.

  Moreover, according to the measuring apparatus of Claim 2, since the comparison value can be arbitrarily set, the comparison value is changed according to the type of the measurement object and the type of electrical equipment connected to the measurement object. By doing so, it is possible to reliably grasp the degree of the physical quantity of the measurement target object in various types of usage in which the types of measurement target object and electrical equipment are different.

1 is a configuration diagram showing a configuration of a current measuring device 1. FIG. 2 is a configuration diagram showing a configuration of a range amplifier 11. FIG. 3 is a flowchart of a measurement process 40. 4 is a first explanatory diagram illustrating a display screen of the display unit 5. FIG. 6 is a second explanatory diagram illustrating a display screen of the display unit 5. FIG.

  Hereinafter, embodiments of a measuring apparatus according to the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the current measuring device 1 as an example of the measuring device will be described. The current measuring apparatus 1 shown in FIG. 1 is configured to be able to measure a current value of a current flowing through a power supply line 100 as a measurement object (an example of a physical quantity for the measurement object, for example, an alternating current). In addition, the current measuring apparatus 1 has an auto range function that automatically switches a measurement range suitable for a current value to be measured from a plurality of measurement ranges. Specifically, the current measuring device 1 includes a current sensor 2, a signal processing circuit 3, a comparison unit 4, a display unit 5, an operation unit 6, and a control unit 7, as shown in FIG.

  The current sensor 2 is a clamp-type current sensor. As shown in FIG. 1, the current sensor 2 detects a current flowing through the power supply line 100 in a state of surrounding (clamping) the power supply line 100 and corresponds to the current value. AC voltage Va (analog signal) having a voltage value to be output is output.

  As shown in FIG. 1, the signal processing circuit 3 includes a range amplifier 11, a low-pass filter 12, a capacitor 13, an RMS (Root Mean Square) / DC converter 14, an amplifier 15, and an AC / DC converter 16. A conversion process for converting the AC voltage Va output from the sensor 2 into the voltage data Dv is executed.

  As an example, as shown in FIG. 2, the range amplifier 11 includes an operational amplifier 21, resistors 22a to 22c (hereinafter also referred to as “resistor 22” when not distinguished), a resistor 23, and switches 24a to 24c (hereinafter referred to as not distinguished). (Also referred to as “switch 24”). The operational amplifier 21 amplifies the AC voltage Va output from the current sensor 2 under the control of the control unit 7. The resistors 22 a to 22 c are ranges switching resistors having different resistance values, and one or more of these resistors are connected to the negative feedback path of the operational amplifier 21 by the switch 24. The resistor 23 functions as a reference resistor for determining the gain of the operational amplifier 21. Therefore, the operational amplifier 21 generates the AC voltage Va with a gain determined by one or more resistance values of the resistors 22a to 22c connected to the negative feedback path of the operational amplifier 21 by the switches 24a to 24c and the resistance value of the resistor 22d. Amplify.

  The low-pass filter 12 receives the AC voltage Va amplified by the range amplifier 11 and passes a frequency component lower than the sampling clock of the A / D converter 16 (for example, a frequency component equal to or less than ½ of the sampling clock). . The capacitor 13 is a capacitor for removing a DC component, and removes the DC component contained in the AC voltage Va that has passed through the low-pass filter 12.

  The RMS / DC converter 14 performs RMS conversion on the AC voltage Va that has passed through the low-pass filter 12 and the capacitor 13 and outputs a DC voltage Vc. The amplifier 15 amplifies the DC voltage Vc output from the RMS / DC converter 14. As an example, the A / D converter 16 is a double integration type A / D converter, and converts the DC voltage Vc (analog signal) amplified by the amplifier 15 from analog to digital at a predetermined sampling period. Voltage data Dv (digital signal) is output.

  The comparison unit 4 includes a comparator 31 and a power supply unit 32. As an example, the comparator 31 includes a differential amplifier. In this case, the comparator 31 compares the voltage value of the comparison voltage Vref input to the inverting input terminal with the voltage value of the AC voltage Va output from the current sensor 2 and input to the non-inverting input terminal, and AC When the voltage value of the voltage Va is higher than the voltage value of the comparison voltage Vref, a comparison process for outputting a comparison result signal S1 (a high level signal as an example) indicating the comparison result is executed. The power supply unit 32 generates the comparison voltage Vref used for the comparison process by the comparator 31 under the control of the control unit 7.

  For example, the display unit 5 includes a liquid crystal panel and displays various images according to the control of the control unit 7. Further, as shown in FIG. 4, display areas A1 and A2 are set in the display unit 5. In this case, as shown in the figure, the comparison result image Gc indicating the comparison result by the comparison unit 4 is displayed in the display area A1, and as shown in FIG. 5, the display area A2 is measured by the control unit 7. A measured value image Gm indicating the current value (measured value) is displayed. The operation unit 6 includes various operation buttons, and outputs an operation signal S2 corresponding to the operation of each operation button to the control unit 7.

  The control unit 7 controls the signal processing circuit 3, the comparison unit 4, and the display unit 5 according to the operation signal S <b> 2 output from the operation unit 6. The control unit 7 constitutes a measurement unit together with the signal processing circuit 3, and based on the voltage data Dv as a digital signal obtained by analog-digital conversion of the AC voltage Va as an analog signal output from the current sensor 2, the power line The current value of the current flowing through 100 is measured. In addition, the control unit 7 executes a first display process for displaying the measurement value image Gm on the display unit 5 and performs a second display process for displaying the comparison result image Gc on the display unit 5.

  Next, a method for measuring the current value of the current flowing through the power supply line 100 using the current measuring device 1 and the operation of the current measuring device 1 at that time will be described with reference to the drawings. As shown in FIG. 1, it is assumed that the power line 100 is connected to a commercial power source (not shown) via a breaker 300.

  Prior to the measurement, the operation unit 6 is operated to input, for example, “10.00 mA” as the set value Is. This set value Is is a current value for allowing the user to know how large the current value of the current flowing through the power supply line 100 is (see FIG. 4), and is executed by the control unit 7. In the second display process, a comparison result image Gc indicating whether or not the current value of the current flowing through the power supply line 100 exceeds the set value Is is displayed on the display unit 5.

  Next, the control unit 7 specifies the comparison voltage Vref of the voltage value corresponding to the input set value Is based on the operation signal S2 output from the operation unit 6, and controls the power supply unit 32 of the comparison unit 4 Then, the output voltage of the power supply unit 32 is set to the specified comparison voltage Vref.

  Next, as shown in FIG. 1, the current sensor 2 surrounds (clamps) the power supply line 100. Next, the operation unit 6 is operated to instruct the start of measurement. At this time, the control unit 7 executes the measurement process 40 shown in FIG. 3 according to the operation signal S2 output from the operation unit 6. In this measurement process 40, the control unit 7 shifts each component constituting the signal processing circuit 3 to a standby state for starting the execution of the conversion process (step 41). Further, the control unit 7 shifts each component constituting the comparison unit 4 to a standby state for starting the comparison process (step 42). Subsequently, the control unit 7 repeatedly executes a process of determining whether or not the comparison result signal S1 is output from the comparison unit 4 at a predetermined time interval (step 43).

  Next, as shown in FIG. 1, the electrical equipment 200 is connected to the power line 100 and operated. In this case, in a state where the electrical device 200 operates normally without a failure, a current corresponding to power consumption flows through the power supply line 100 and is supplied to the electrical device 200. At this time, the current sensor 2 surrounding the power supply line 100 detects a current flowing through the power supply line 100 and outputs an AC voltage Va corresponding to the current value.

  At this time, in the comparison unit 4 in the standby state, the comparator 31 performs a comparison process, and compares the voltage value of the comparison voltage Vref input to the inverting input terminal and the AC voltage Va output from the current sensor 2. Compare the voltage value. Specifically, the comparator 31 outputs the comparison result signal S1 when the voltage value of the AC voltage Va is higher than the voltage value of the comparison voltage Vref, and the voltage value of the AC voltage Va is equal to or less than the voltage value of the comparison voltage Vref. Sometimes, the output of the comparison result signal S1 is stopped. In this case, when the comparison result signal S1 is output from the comparator 31, the control unit 7 executes the second display process (step 44). In the second display process, the control unit 7 indicates that the current value exceeds the set value Is (10.00 mA in this example) as shown in FIG. 4 as an image showing the comparison result by the comparison unit 4. Is displayed in the display area A <b> 1 of the display unit 5. Subsequently, the control unit 7 repeatedly executes a process of determining whether or not the voltage data Dv is output from the signal processing circuit 3 at a predetermined time interval (step 45).

  On the other hand, in the signal processing circuit 3 in the standby state, when the AC voltage Va is output from the current sensor 2, the range amplifier 11 amplifies the AC voltage Va. In this case, the control unit 7 controls the switch 24 of the range amplifier 11 to connect the resistor 22 having the maximum resistance value among the resistors 22a to 22c to the negative feedback path of the operational amplifier 21, thereby setting the measurement range. Set to the minimum range.

  Next, the low-pass filter 12 inputs the AC voltage Va amplified by the range amplifier 11 and passes a low frequency component, and the capacitor 13 converts the DC component contained in the AC voltage Va passed through the low-pass filter 12. Remove. Subsequently, the RMS / DC converter 14 RMS-converts the AC voltage Va that has passed through the low-pass filter 12 and the capacitor 13 and outputs a DC voltage Vc. The amplifier 15 outputs the DC voltage Vc output from the RMS / DC converter 14. Amplify. Next, the A / D converter 16 performs analog-digital conversion on the DC voltage Vc amplified by the amplifier 15 and outputs voltage data Dv.

  Next, the control unit 7 specifies the value of the current flowing through the power supply line 100 based on the voltage data Dv output from the A / D converter 16. In this case, when the specified current value exceeds the measurement range initially set for the range amplifier 11, the control unit 7 controls the switch 24 to connect the resistance first connected to the negative feedback path of the operational amplifier 21. A resistor 22 having a resistance value next to 22 is connected to the negative feedback path, and the measurement range is switched to one larger than the initially set measurement range. At this time, the low-pass filter 12, the capacitor 13, the RMS / DC converter 14, the amplifier 15 and the A / D converter 16 operate as described above, whereby the voltage data Dv is output.

  Subsequently, the control unit 7 specifies the value of the current flowing through the power supply line 100 based on the voltage data Dv. In this case, when the specified current value exceeds the second set measurement range, the control unit 7 switches the connection of the resistor 22 to switch to a larger measurement range. Thereafter, the control unit 7 similarly switches the measurement range until the specified current value falls within the set measurement range. Next, when the specified current value falls within the set measurement range, the current value is determined as the measurement value, and the control unit 7 executes the first display process (step 46). In the first display process, the control unit 7 displays a measurement value image Gm indicating a current value (in this example, 12.42 mA) determined as a measurement value in the display area A2 of the display unit 5, as shown in FIG. Display.

  Here, the A / D converter 16 of the current measuring apparatus 1 is a double integration type A / D converter, and executes discharging of the capacitor, normal integration, and reverse integration as one process. In this case, generally, in order to reduce the influence of hum noise, each of the forward integration and the reverse integration requires about 100 msec. In addition, a certain amount of time is required for discharging the capacitor. For this reason, at least about 200 msec is required for one process in which the A / D converter 16 converts the DC voltage Vc from analog to digital and outputs the voltage data Dv. Therefore, as described above, when the measurement range is switched, a time of about the number of measurement ranges × 200 msec is required until the current value is determined, and as a result, the electrical equipment 200 is connected to the power line 100. It takes about 200 msec to 1 sec before the current value is displayed on the display unit 5. On the other hand, the comparison process by the comparison unit 4 does not include a process that requires a relatively long time such as discharge of the capacitor, normal integration, and reverse integration, and thus ends in about several milliseconds to 10 milliseconds. For this reason, the comparison result image Gc is displayed on the display unit 5 in about several milliseconds to 10 milliseconds after the electrical equipment 200 is connected to the power line 100. As a result, in this current measuring apparatus 1, the comparison result image Gc is displayed in a short time after the electrical equipment 200 is connected to the power supply line 100, and then the current value is displayed.

  On the other hand, for example, when the electrical device 200 in which a failure such as a short circuit has occurred in the electric circuit is connected to the power supply line 100, an excessive current flows in the power supply line 100. At this time, the breaker 300 connected to the power supply line 100 is activated and the supply of power is stopped. In this case, the operation time of the breaker 300 is generally about 100 msec (the electric equipment technical standard specifies that the operation time at the rated operation current is within 100 msec). For this reason, when a time of about 100 msec has elapsed since the electrical device 200 is connected to the power supply line 100, the current in the power supply line 100 is stopped, and accordingly, the output of the AC voltage Va from the current sensor 2 is also stopped. To do. Therefore, in this case, the first display process that requires a time of 200 msec or longer after the electrical equipment 200 is connected to the power supply line 100 is not executed, and the display area A2 of the display unit 5 is in a non-display state. Maintained.

  On the other hand, since the comparison processing by the comparison unit 4 is completed in about several milliseconds to 10 milliseconds, even if the breaker 300 is operated by connecting the electric device 200 in which a failure has occurred to the power line 100, 100 milliseconds for the breaker 300 to operate. Before the time elapses, the comparison result signal S1 is output. Therefore, in this current measuring apparatus 1, even in such a case, the second display process is executed and the comparison result image Gc is displayed in the display area A1, so that the current flows to the power supply line 100 before the breaker 300 operates. It is possible to make the user surely grasp whether or not the current value of the current that has been exceeded is equal to or greater than the set value Is.

  As described above, the current measuring apparatus 1 includes the comparison unit 4 that compares the value of the AC voltage Va with the predetermined value of the comparison voltage Vref and outputs the comparison result signal S1 as a comparison result, and includes a control unit. 7 executes a second display process for displaying the comparison result image Gc indicating the comparison result on the display unit 5 based on the comparison result signal S1 output from the comparison unit 4. In this case, since the comparison unit 4 outputs the comparison result without performing the conversion process for converting the AC voltage Va into a digital signal (digital data), the comparison process for outputting the comparison result is performed from the time when the breaker 300 operates. Even can be executed in a short time. Therefore, according to the current measuring device 1, even when the electric device 200 in which a failure such as a short circuit has occurred in the electric circuit is connected to the power supply line 100 as the measurement object, the power supply line is not yet activated before the breaker 300 is activated. As a result of being able to display in a short time whether or not the current value of the current flowing through 100 is equal to or greater than the set value Is, it is possible to reliably tell the user how much current has flowed through the power supply line 100. It can be grasped.

  Further, according to the current measuring apparatus 1, the configuration is such that the comparison voltage Vref (the set value Is corresponding to the comparison voltage Vref) can be set to an arbitrary value, so that the type of the measurement object and the measurement object are connected. By changing the comparison voltage Vref according to the type of electrical equipment to be used, it is possible to reliably grasp how much current is flowing through the measurement target in various types of usage with different types of measurement target and electrical equipment. be able to.

  In addition, although the example which detects the electric current which flows through the power supply line 100 non-contactingly using the clamp type current sensor 2 was mentioned above, a probe is made to contact the exposed part of the power supply line 100, and an electric current is directly sent to the signal processing circuit 3. An input configuration can also be adopted. Further, the configuration example in which the comparison result image Gc and the measurement value image Gm are separately displayed in the different display areas A1 and A2 in the display unit 5 has been described above, but the comparison result image Gc and the measurement value image Gm are sequentially displayed in one display area. It is also possible to adopt a configuration for displaying on the screen. In this configuration, the comparison result image Gc is displayed in a predetermined display area of the display unit 5 by the second display process that is completed first, and then replaced with the comparison result image Gc when the current value is determined. The measurement value image Gm can be displayed in the display area.

  Moreover, although the example provided with the measurement range automatic switching (auto-range switching) function has been described above, it can be applied to a configuration in which the measurement range is manually switched or a configuration in which the measurement range is fixed to one type.

  In addition, the configuration example in which the current value of the current flowing through the power supply line 100 is measured as a physical quantity for the measurement object is described above, but the present invention is not limited to this. For example, the resistance value, voltage value, power value, The present invention can be applied to various measuring devices that measure physical quantities such as rotation speed and flow rate.

DESCRIPTION OF SYMBOLS 1 Current measuring device 3 Signal processing circuit 4 Comparison part 5 Display part 7 Control part 100 Power supply line Dv Voltage data Gm Measurement value image Is Setting value S1 Comparison result signal Va AC voltage Vref Comparison voltage

Claims (2)

A control unit that measures a physical quantity of a measurement object based on a digital signal obtained by analog-digital conversion of an input analog signal, and a control that executes a first display process for displaying the physical quantity measured by the measurement unit on a display unit A measuring device comprising a section,
A comparison unit that compares the value of the analog signal with a predetermined comparison value and outputs a comparison result,
The said control part is a measuring apparatus which performs the 2nd display process which displays the said comparison result output from the said comparison part on the said display part.   The current measurement device according to claim 1, wherein the comparison value is configured to be arbitrarily set.

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