TWI414804B - System and method for verifying a multimeter - Google Patents

Abstract

A method for verifying a multimeter is provided. The method includes: setting a grade place of a multimeter; a calibration device outputting analog signals according to the grade place; the multimeter transforming the analog signals to digital signals and displaying a value expressed by the digital signals; shooting a picture of the value; getting the value from the picture; detecting if a mean value of values from all pictures shot is in a permissible error range of the multimeter; and generating a report according to the detection. A system for verifying a multimeter is also provided.

Description

Multimeter calibration system and method

The invention relates to a calibration system and method, in particular to a multimeter calibration system and method.

Handheld multimeters have been widely used, and the accuracy requirements for handheld multimeters are increasing. Therefore, the calibration accuracy of the multimeter has become an important issue.

At present, since the multimeter has no external interface, the calibration of the multimeter needs to manually input the value displayed by the multimeter into the computer. When verifying the different positions of the multimeter, manual manual shifting is required, and all the checkpoints are verified. After that, it is necessary to manually record the data, make a verification report, waste a lot of manpower, and reduce the work efficiency.

In view of the above, it is necessary to provide a multimeter calibration system and method, which can effectively verify the multimeter.

A multimeter calibration system includes a calibration source and a computer connected to the calibration source. The calibration source is connected to a multimeter to be verified. The computer is connected with a camera and a robot arm for adjusting the multimeter to be verified. a calibration source for outputting an analog signal to the multimeter according to the adjusted gear position; the multimeter is configured to convert the analog signal into a digital signal and display a value expressed by the digital signal; the camera is used to photograph the multimeter The displayed value gets the picture; and the computer is used to get the image The value in the captured picture determines whether the average value of the values in the captured picture is within the allowable error range of the multimeter, and generates a verification report based on the determination result.

A multimeter calibration method, the method comprising the steps of: adjusting a multimeter to a gear position to be verified; the calibration source outputs an analog signal to the multimeter according to the adjusted gear position; the multimeter converts the analog signal into a digital signal, and displays the The value expressed by the digital signal; capture the value displayed by the multimeter; obtain the value in the captured picture; determine whether the average value of the values in all the pictures taken is within the allowable error range of the multimeter; and generate the school based on the above judgment result Report.

Compared with the prior art, the multimeter calibration system and method can control the multimeter calibration process by the whole computer, thereby improving work efficiency and saving working time.

1‧‧‧ multimeter

2‧‧‧ Calibration source

3‧‧‧Measurement control box

4‧‧‧ computer

5‧‧‧ camera

6‧‧‧ Robotic arm

S20‧‧‧The mechanical arm adjusts the position of the multimeter to the position to be verified

S22‧‧‧Measurement control box closes the corresponding switch according to the gear position to be verified

S24‧‧‧ calibration source sends an analog signal to the multimeter

The S26‧‧‧ multimeter converts the analog signal into a digital signal and displays the value expressed by the digital signal

S28‧‧‧ Camera shoots the value displayed by the multimeter

S30‧‧‧ computer gets the value in the picture taken

Is the average value of the values stated in S32‧‧‧ within the tolerance of the multimeter?

S34‧‧‧ indicates that the multimeter has errors

Have the S36‧‧‧ multimeter calibration positions been verified?

S38‧‧‧ Generate verification report

1 is a hardware architecture diagram of a preferred embodiment of the multimeter calibration system of the present invention.

2 is a flow chart showing the operation of the preferred embodiment of the multimeter calibration method of the present invention.

Figure 3 is a flow diagram of a preferred embodiment of a computer to obtain values in a picture.

FIG. 4 is the first picture taken by the camera in step S300 of FIG. 3.

FIG. 5 is a second picture taken by the camera in step S304 of FIG. 3.

FIG. 6 is a schematic diagram of a new picture obtained by the difference method in step S306 of FIG. 3.

FIG. 7 is a schematic diagram of obtaining the vertex coordinates of the M segment of the eight-segment code character in the new picture by S308 in FIG. 3.

Figure 8 is a schematic diagram of the truth table.

As shown in FIG. 1, it is a hardware architecture diagram of a preferred embodiment of the multimeter calibration system of the present invention. The system includes: a multimeter 1, a calibration source 2, a measurement control box 3, a computer 4, a camera 5, and a robot arm 6.

Both the multimeter 1 and the calibration source 2 comprise a plurality of gear positions, such as an AC voltage gear. Wherein, the gear position of the multimeter 1 and the gear position of the calibration source 2 correspond to each other, and the corresponding gear position is connected through a switch of the measurement control box 3, for example, the AC voltage file of the multimeter 1 transmits through one of the measurement control boxes 3 The switch is connected to the AC voltage file of calibration source 2.

The calibration source 2 and the measurement control box 3 are respectively connected to the computer 4 through a serial port, such as an RS232 serial port. When the switch of the measurement control box 3 is closed, the measurement control box 3 sends a signal to the computer 4 notifying the computer 4 that the switch is closed. After receiving the signal, the computer 4 sends a command to the calibration source 2, so that the calibration source 2 sends an analog signal to the multimeter 1. The analog signal in this embodiment may be a voltage signal or a current signal. The multimeter 1 is further configured to convert the analog signal into a digital signal and display the value expressed by the digital signal.

In this embodiment, the camera 5 can be connected to the computer 4 through the usb interface, or can be built in the computer 4. The camera 5 is used to capture the numerical values displayed by the multimeter 1. Specifically, the camera 5 is photographed once every t time. In the preferred embodiment, t = 200 ms. The computer 4 is configured to analyze the picture taken by the camera 5 to obtain a verification result, and generate a verification report based on the verification result. In addition, the computer 4 is connected to the robot arm 6 through a serial port, which is used to control the robot arm 6 to adjust the gear position of the multimeter 1.

As shown in FIG. 2, it is a flowchart of the operation of the preferred embodiment of the multimeter calibration method of the present invention.

In step S20, the robot arm 6 adjusts the gear position of the multimeter 1 to the gear position to be verified.

In step S22, the measurement control box 3 closes the corresponding switch according to the gear position to be verified. For example, in step S20, if the robot arm 6 adjusts the gear position of the multimeter 1 to the AC voltage range, the measurement control box 3 closes the switch that connects the AC voltage level of the multimeter 1 with the AC voltage level of the calibration source 2.

In step S24, after the switch is closed, the calibration source 2 sends an analog signal to the multimeter 1. In this embodiment, the analog signal can be a voltage signal or a current signal. For example, if the switch of the measurement control box 3 connected to the AC voltage file is closed in step S22, the analog signal is a voltage signal.

Step S26, after receiving the analog signal, the multimeter 1 converts the analog signal into a digital signal and displays the value expressed by the digital signal.

In step S28, the camera 5 captures the numerical value displayed by the multimeter 1. In this embodiment, the camera 5 captures the numerical value displayed by the multimeter 1 every 200 ms, and takes a total of ten shots.

In step S30, the computer 4 acquires the value in the captured picture.

In step S32, the computer 4 determines whether the average value of the numerical value is within the allowable error range of the multimeter 1. If the average value is not within the allowable error range of the multimeter 1, the multimeter 1 is prompted to be in error in step S34, that is, the check result is the multimeter 1 out of tolerance, and then proceeds to step S38. The average value refers to a value obtained by adding values in all the pictures taken by the camera 5 and dividing by the number of pictures. For example, if the camera 5 has taken a total of 10 pictures, the average value is equal to the sum of the values displayed by the 10 pictures divided by 10.

Step S36, when the average value is within the allowable error range of the multimeter 1, The verification result is that the multimeter 1 passes the verification, and the computer 4 judges whether the gears that need to be verified by the multimeter 1 have been verified. If there is no verification that the multimeter 1 needs to be verified, the process goes to step S20. If the gears of the multimeter 1 that need to be verified have been verified, the process proceeds to step S38.

In step S38, the computer 4 generates a verification report based on the verification result.

As shown in FIG. 3, a flow chart of a preferred embodiment of the computer 4 to obtain values in a picture.

In step S300, the camera 5 captures the numerical value currently displayed by the multimeter 1 as the first picture. As shown in FIG. 4, the first picture shows 0.2, that is, the value displayed by the multimeter 1 is 0.2.

In step S302, the calibration source 2 re-outputs another analog signal to the multimeter 1 according to the command sent by the computer 4. The multimeter 1 converts the analog signal into a digital signal and displays the value expressed by the digital signal.

In step S304, the camera 5 captures the numerical value displayed by the multimeter 1 in step S302 to obtain a second picture. As shown in FIG. 5, the second picture shows 8.21, that is, the value displayed by the multimeter 1 is 8.21.

In step S306, the computer 4 obtains a new picture by using the difference method. The subtraction method refers to subtracting the image displayed by the first picture and the second picture, and the obtained result image is the new picture. For example, subtracting the images displayed by the two pictures in FIGS. 5 and 4 results in a new picture as shown in FIG. 6. In this embodiment, whether it is the first picture, the second picture, or the new picture, the characters constituting each value are composed of eight segments, that is, all eight segment code characters.

In step S308, the computer 4 acquires the vertex coordinates of the segments constituting each eight-segment code character in the new picture. As shown in FIG. 7, the eight-segment code character 8 is displayed in the new picture, this embodiment Taking the vertex coordinates of the M segment in the eight-segment code character 8 as an example, if the point O in the upper left corner of the new picture is taken as the origin coordinate system, the four vertex coordinates of the rectangular ABCD constituting the M segment are described. It is: A(x1, y2), B(x2, y2), C(x2, y1), D(x1, y1).

Step S310, searching for the position corresponding to each segment of the eight-segment code character on the first picture and the second picture by using the obtained vertex coordinates. For example, the position corresponding to the M segment is found in the second picture described in FIG.

Step S312, calculating an average luminance Fi of all the primitive points constituting each segment in the eight-segment code character. For example, if the segment representing the eight-segment code character is represented by i, i is a value of 1 to 8, and the M segment can be defined as The first segment, i = 1, then F1 represents the average brightness of all the feature points in the M segment.

In step S314, the brightness average value Fr of the reference area is calculated. The reference area refers to the area of the picture in which all eight-segment code characters are removed.

In step S316, it is determined whether |Fi-Fr| is greater than a threshold. The threshold can be set by itself. In the preferred embodiment, the threshold is 125 steps. When the |Fi-Fr| is greater than the threshold, the process proceeds to step S318; when |Fi-Fr| is not greater than the threshold, the process proceeds to step S320.

In step S318, it is determined that the state of the segment is a bright state. For example, F1 is an average brightness of the M segment, and when |F1-Fr| is greater than the threshold, the M segment is confirmed to be a bright state.

In step S320, it is determined that the state of the segment is a dark state.

Step S322, the value in each picture is obtained by using the truth table according to the light and dark state of each segment, and the truth table is as shown in FIG. The pictures include a first picture and a second picture.

In the present embodiment, "1" shown in FIG. 8 represents a bright state, and "0" represents a dark state.

It should be noted that, in the two pictures taken in the above steps, at least one character in the new picture obtained by the difference method is 8 to accurately locate each eight-segment code character.

The above is only the preferred embodiment of the present invention, and has been used in a wide range of applications. Any other equivalent changes or modifications which are not departing from the spirit of the present invention should be included in the following claims. Inside.

S20‧‧‧The mechanical arm adjusts the position of the multimeter to the position to be verified

S22‧‧‧Measurement control box closes the corresponding switch according to the gear position to be verified

S24‧‧‧ calibration source sends an analog signal to the multimeter

The S26‧‧‧ multimeter converts the analog signal into a digital signal and displays the value expressed by the digital signal

S28‧‧‧ Camera shoots the value displayed by the multimeter

S30‧‧‧ computer gets the value in the picture taken

Is the average value of the values stated in S32‧‧‧ within the tolerance of the multimeter?

S34‧‧‧ indicates that the multimeter has errors

Have the S36‧‧‧ multimeter calibration positions been verified?

S38‧‧‧ Generate verification report

Claims (9)

A multimeter calibration system includes a calibration source and a computer connected to the calibration source, the calibration source being connected to a multimeter to be verified, the computer being connected with a camera and a robot arm, wherein the robot arm is used to adjust the multimeter The calibration gear is used to output an analog signal to the multimeter according to the adjusted gear position; the multimeter is used to convert the analog signal into a digital signal and display the value expressed by the digital signal; the camera is used to capture the The value displayed by the multimeter obtains a picture; the computer is used to subtract the picture taken by the camera by the difference method to obtain a new picture, and obtain the vertex coordinates of each segment constituting each eight-segment code character in the new picture. And using the vertex coordinates to find the position corresponding to each segment of the eight-segment code character on the captured picture, and calculating the average brightness Fi of each segment in the eight-segment code character in the captured picture, and Calculating the average brightness Fr of the reference area, when |Fi-Fr| is greater than a set threshold, determining that the section is in a bright state, and when |Fi-Fr| is not greater than the threshold, determining the In the dark state, and using the truth table according to the light and dark state of each segment of the eight-segment code character to obtain the value in each picture; and determining whether the average value of the value in the captured picture is within the allowable error range of the multimeter And generate a verification report based on the judgment result. For example, in the multimeter verification system described in claim 1, the average value is a value obtained by dividing the values in all the captured pictures and dividing by the number of pictures. The multimeter calibration system according to claim 1, wherein the system further comprises a measurement control box connected to the computer via a serial port, the measurement control box comprising a plurality of switches, each of which is used for connection The calibration source and the corresponding position of the multimeter, and when the switch of the measurement control box is closed, the measurement control box is configured to send a signal to the computer to notify the computer The switch is closed and the computer sends a command to the calibration source after receiving the signal. For example, in the multimeter verification system described in claim 1, the at least one character in the new picture is 8. The multimeter verification system according to claim 1, wherein the reference area is an area in the picture in which all eight codeword characters are removed. A multimeter calibration method based on the verification system described in claim 1 of the patent scope, the method comprising the steps of: adjusting a multimeter to a gear position to be verified; and the calibration source outputting an analog signal to the multimeter according to the adjusted gear position; The multimeter converts the analog signal into a digital signal, and displays the value expressed by the digital signal; captures the value displayed by the multimeter to obtain a picture; subtracts the picture taken by the camera by the difference method to obtain a new picture, obtains the The vertex coordinates of each segment of each eight-segment code character are formed in the new picture, and the position corresponding to each segment of the eight-segment code character is found on the captured picture by using the vertex coordinates, and the captured image is calculated. The average brightness Fi of each segment is formed in the eight-segment code character in the picture, and the average brightness Fr of the reference area is calculated. When |Fi-Fr| is greater than a set threshold, the segment is judged to be in a bright state, when |Fi-Fr When the threshold is not greater than the threshold, it is determined that the segment is in a dark state, and the value in each picture is obtained by using a truth table according to the light and dark state of each segment of the eight-segment code character; determining all the pictures taken Whether the average value of the value is within the allowable error range of the multimeter; and generating a verification report based on the above judgment result. For example, in the multimeter calibration method described in claim 6, the step of generating a verification report according to the judgment result includes: when the average value of the values in all the captured pictures is within the allowable error range of the multimeter, determining the The multimeter passes the check; or When the average value of the values in all the pictures taken is not within the allowable error range of the multimeter, it is determined that the multimeter is out of tolerance. For example, in the multimeter verification method described in claim 6, the average value is a value obtained by adding the values in all the captured pictures and dividing by the number of pictures. For example, in the multimeter verification method described in claim 6, the at least one character in the new picture is 8.