该HC-SR04超声波传感器使用声纳来确定距离的对象 - 就像蝙蝠或海豚做。
测距距离：2厘米- 400厘米/ 1“ - 16英尺
This little sensor is Not compatible with the APM series of autopilots (yet).
There have being made a few attempts to make it work with APM but it does not worth the effort.
If you are looking for an APM sonar sensor try something else.I've found the schema: http://uglyduck.ath.cx/ep/archive/2014/01/Making_a_better_HC_SR04_Echo_Locator.html
I've checked my own HC-SR04. The schema is right. But the chip MAX232 is not working correctly. Normally, the transmitter MK2 would be driven by /-10V and mine is 0/ 5V, the MAX232 doesn't oscillate and doesn't generate high voltages.Works as it should with and Arduino. A quick google of HC-SR04 and you can find the library, examples and all you need to use it.Although I have not yet incorporated this sensor into my Multiwii quadcopter, I have been able to find lots of Arduino code online so far. All I really have to do now is figure out which pins to use. Device looks nice and sturdy for what it is.This product is very cheap comparing with other sites but it's less accuracy. honestly, I didn't try the original product to compare between them.Fairly accurate, will need to search google for an arduino library called "NewPing" in order for it to work properlyJust make sure to setup the range to 200 otherwise you will have alt. jumpsThis module can be found on other site for upwards of $15.. Good onya HK for keeping the prices real!First time buying Arduino from HK. Connected it to my breadboard and had it working within minutes using a sample sketch. Search for Ultrasonic SR04 and a bunch of examples come up. Had to make sure it was a sketch for the 4 pin version, and not 3.I connected the sensor up to an Arduino Nano used the Newping library and example code and it worked very well giving reasonably accurate measurements ( within 5-10pcnt ) from 1 inch to about 60ins ( my ceiling ). I plan to use for collision avoidance in a small wheeled robot and am even thinking of using for water level detection in our 5000 gallon rainwater tank. Very good value.