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I want to make a vehicle detection prototype. I find there are multiple choices of sensors that can be used to detect a vehicle, such as acoustic, ultrasonic, infrared, magnetic inductive sensor.

I am only familiar with infrared sensors, which are low cost, can be a good choice of detection of approaching objects, whereas the acoustic and ultrasonic are much more expensive.

However an infrared sensor is not a complete solution. In order to find whether the approaching object is either a vehicle or any other objects, I suppose I need either a magnetic or an inductive sensor. I learned that scalar magnetometers are suitable for the vehicle detection, because it measure the total strength of the magnetic field to which they are subjected. However then I learned that magnetic sensors can be also divided into DC and AC sensors.

in wiki, it says "AC" if they measure fields that vary relatively rapidly in time, and "DC" if they measure fields that vary only slowly (quasi-static) or are static. AC magnetometers find use in electromagnetic systems (such as magnetotellurics), and DC magnetometers are used for detecting mineralisation and corresponding geological structures.

Can anybody explain the difference between DC and AC based magnetometers? Currently my idea is to use a magnetometer with an infrared sensor. What do you think of this approach? My evaluation criteria is performance first, then power consumption, and cost last.

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  • \$\begingroup\$ Vehicle detection???Do you hate Image processing??? \$\endgroup\$ – perilbrain Sep 16 '12 at 15:10
  • \$\begingroup\$ Have you tried searching for information? \$\endgroup\$ – Leon Heller Sep 16 '12 at 15:22
  • \$\begingroup\$ I am now still searching the information on web, to compare different sensors. I am just seeking some more ideas if someone has experience on them. I only worked on the infrared sensor. \$\endgroup\$ – user824624 Sep 16 '12 at 15:47
  • \$\begingroup\$ I am not hating image processing for vehicle detection. However, image processing is kind of costly than the sensor based solution, and I don't want to be offensive to the privacy issue. while image processing solution works on the indoor, I hope to have a sensor based solution on the outdoor . if you know about the streetline or worldsensing, they are using the WSN to detect the vehicle. \$\endgroup\$ – user824624 Sep 16 '12 at 15:50
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    \$\begingroup\$ @user824624: It would help if you clarify what exactly you mean by "detection". Detecting a vehicle's absolute position tracked within an area vs. Detecting when a vehicle passes through a specific area/gateway vs. Detecting when a vehicle comes in proximity of a vehicle \$\endgroup\$ – boardbite Sep 22 '12 at 13:48
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"Vehicle detection loops, called inductive-loop traffic detectors" are one pretty common method. A groove is cut in the pavement, wire is layed in the groove, the groove is filled in with a sealant, and the wires go to a processor which makes the wire act like a metal detector - the vehicle interacts with the e-mag field, and the processor detects that.

Are you allowed to sawcut the area in question? If not, then a different method should be selected. Maybe just tubes across the road as one finds leading into or out of a town so the local municipality can count how many cars are using a road. I imagine they just detect change in air pressure as cars drive over the tubes.

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I don't know much on this subject but I found... https://www.fhwa.dot.gov/publications/publicroads/07nov/04.cfm Sounds like inductive sensors are the most common currently. I don't know where it stands today, but years ago there was interesting research into smart concrete that could detect vehicle weight and location. e.g. https://www.sciencedaily.com/releases/1999/05/990520073311.htm

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