With the rapid growth of domestic automobiles, the problem of fewer vehicles is becoming more and more prominent, and it has become a common concern in the current society. The emergence of intelligent parking system can maximize the utilization of parking spaces, create an orderly environment for on-street parking, and solve the problem that the parking spaces are difficult to find for the owners.
Introduction to the principle of intelligent parking system
The road intelligent parking system is composed of geomagnetic parking space detector, repeater, concentrator, data processing center, city parking space induction, etc., integrating parking space monitoring technology, information release technology, and Internet of Things integration technology to maximize the use of parking spaces. Improve the convenience of citizens' travel and provide effective data protection for urban parking space monitoring and planning. The system architecture diagram is as follows:
The wireless geomagnetic parking space detector uses a magnetic sensor to detect the influence of the vehicle on the geomagnetism in real time to determine whether there is a vehicle parking on the parking space, and transmits the detection data to the repeater by wireless, and the repeater receives multiple wireless geomagnetic vehicles. The information sent by the detector is uploaded to the concentrator, the concentrator manages a range of parking space detectors and repeaters, and the collected parking space status data is uploaded to the monitoring center for centralized management.
Power test analysis
The parking space detector is used as the front end of the digital detection. The magnetic sensor is used to detect the influence of the vehicle on the geomagnetism in real time. When there is a vehicle stopping, the magnetic field distortion is different to judge, reflected in the electrical signal, when no vehicle passes, the parking space detector When the work is in the standby state, the standby current is below 20μA. When the vehicle is detected, the detection number is required to be uploaded to the concentrator. At this time, the parking position detector works in the transmitting state, and the current is up to several A, as shown in the following figure:
In this case, the power consumption test of the parking space detector is a major difficulty. First, the standby current is too small. Take the PA310 power meter of Guangzhou Zhiyuan as an example. The minimum range of the PA310 is 5 mA. The minimum measurable precision current is the range of 1 %, ie 5mA*0.01=50μA, the standby current cannot be tested directly with the PA310. At the same time, the difference between the standby current and the emission current is large. In the automatic range mode, the power meter rises from a small current to a large current, which is gradually traversing the middle. The range is a waste of time and affects the accuracy of voltage and current integration. However, the parking space detector is battery-powered and has strict requirements on power consumption specifications and battery power supply time at the factory, so accurate power consumption testing is very important.
Power test scheme
When the parking position detector is in standby mode, the standby current is as small as 20μA. The PA310 power meter is used directly, and the minimum gear position is set to 5mA. The minimum precision current that can be tested is 50μA, and the standby current cannot be accurately tested. Set the constant current source as follows:
Set the constant current source output constant current value (such as 50μA), superimpose the current value and the current of the parking position detector, then input the PA310 power meter to measure, and set the integral mode to test the voltage and current integral value for a period of time. The power consumption of the constant current source is removed, and the power consumption of the parking space detector for a certain period of time is calculated. At the same time, since the difference between the standby current and the emission current is large, during the measurement process, the range skip function is enabled, and the current range can be directly skipped to the specified range, which can reduce the measurement data loss when switching ranges one by one. Improve power measurement accuracy. (Note: Since the internal resistance of the PA310 power meter is mΩ, the current can be introduced by means of an external power supply + MΩ precision resistor instead of the constant current source).
In consumer electronics and wireless mobile devices, battery power is required to be greener and more energy efficient, and high sensitivity, low current measurements are increasingly needed to ensure that the current consumption of these devices is within acceptable limits. In order to maximize battery life, engineers need to minimize power consumption during the life of the product. The low-power test solution for parking space detectors provided above meets the requirements of external current sources and set-range skipping. The need for small current measurements with a wide dynamic range.
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