# Pointer Meter Recognition Method Based on Yolov7 and Hough Transform
## 1 Introduction  
The substation is in a very important position in the power system, and its main task is to convert and distribute electric energy. The normal operation and safety maintenance of substations are issues that need to be paid close attention to in daily inspections. The readings of the meters in the substation can reflect the operation of many pieces of equipment. However, due to the complex external environment of the meter, the large number, and the dependence of the original equipment of the substation on the meter, traditional substation inspection cannot effectively guarantee the real-time validity of the meter reading [1]. The main method of traditional substation inspection is manual inspection and recording. The operator manually judges to read the pointer reading, which requires the operator to have a high level of technology and experience, so it is inevitably interfered with by many human factors, such as the operation angle of the operator observing the dial, the error caused by the observation distance, the long and boring recognition process, and visual fatigue are easily affected by subjective factors, resulting in low work efficiency and inaccurate and wrong recognition results [2]. Traditional substation manual inspection requires personnel to inspect each meter one by one and record data manually. This method requires a lot of time and labor costs, especially in large substations where the inspection process is more cumbersome and time-consuming. The substation environment is complex and there are certain safety risks, such as high-voltage electricity and explosions. During manual inspections, staff need to frequently contact high-voltage equipment, which poses certain safety risks and may cause casualties. Manual inspection can perform only regular inspections on the meters and cannot realize real-time monitoring of the meters, so it is difficult to quickly find and deal with abnormalities in the meters. There are many meters in a substation, such as an oil temperature meter, pressure meter, ammeter, and so on. There are two common types of gauges: digital and analog. Figure 1 shows the digital and analog meters. These two types of meters have different characteristics. In the meter industry, the share of digital meters is increasing, because they have the advantages of easy reading and high precision; however, digital meters are not suitable in some special circumstances, such as harsh dust and oil environments. Compared to the digital meter, the pointer meter has greater advantages in this respect, such as being dustproof and waterproof, and having antifreeze, anti-interference, simple structure, low price, strong anti-interference ability, etc. [2]. Pointer meters are widely used in industrial production, automobile manufacturing, electric power industry, and other fields. They are mainly used to measure and display various physical quantities, such as current, voltage, temperature, and pressure, etc. Although digital meters are gradually replacing analog meters, there are still many analog meters in operation in remote areas and developing countries because of the high cost and time-consuming nature of replacing the meters [3]. However, there are still some challenges in pointer meter recognition technology. The pointer shapes and colors of pointer meters are very different, which makes it difficult to accurately classify and locate all pointers in image recognition and processing. Analog gauges are typically used in a variety of lighting conditions, such that changes in ambient lighting may affect the recognition of the pointer's position. In addition, background noise, such as reflections, shadows, etc., will also affect pointer recognition, and these factors affect the recognition accuracy of meter readings.