The SRF02 is a single transducer ultrasonic rangefinder in a small footprint PCB. It features both I2C and a Serial interfaces. The serial interface is a standard TTL level UART format at 9600 baud,1 start, 2 stop and no parity bits, and may be connected directly to the serial ports on any microcontroller. Up to 16 SRF02's may be connected together on a single bus, either I2C or Serial. New commands in the SRF02 include the ability to send an ultrasonic burst on its own without a reception cycle, and the ability to perform a reception cycle without the preceding burst. This has been as requested feature on our sonar's and the SRF02 is the first to see its implementation. Because the SRF02 uses a single transducer for both transmission and reception, the minimum range is higher than our other dual transducer rangers. The minimum measurement range varies from around 17-18cm (7 inches) on a warm day down to around 15-16cm (6 inches) on a cool day. Like all our rangefinders, the SRF02 can measure in uS, cm or inches.

Specification

• Range: 16cm to 6m.
• Power: 5v, 4mA Typ.
• Frequency: 40KHz.
• Size: 24mm x 20mm x 17mm height.
• Analog Gain: Automatic 64 step gain control
• Connection Modes: 1 - Standard I2C Bus 2 - Serial Bus(connects up to 16 devices to any uP or UART serial port)
• Full Automatic Tuning: No calibration, just power up and go
• Timing: Fully timed echo, freeing host controller of task.
• Units: Range reported in uS, mm or inches.

For More Info: https://wiki.dfrobot.com/SRF02_Ultrasonic_sensor__SKU_SEN0005_