User Manual

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URM04V2.0 Ultrasonic Ragner Sensor
55
aa
ADD
2
03
H
L
SUM
PS: The command will return the temperature reading. The return temperature
reading is using Celsius scale.
If the temperature is above 0 Celsius, the first four bits of High will be all 0.
If the temperature is below 0 Celsius, the first four bits of High will be all 1.
The last 4 bits of High together with the Low bits stands for 12bits temperature. The
resolution is 0.1.
When the reading is invalid, it returns 0xFF 0xFF
Example:
Command
0x55 0xaa 0x11 0x00 0x03 0x13(SUM)
Return:
0x55 0xaa 0x11 0x02 0x03 0xF0 0x0A 0x11 (+1 Celsius Degree)
0x55 0xaa 0x11 0x02 0x03 0x00 0x0A 0x20 (-1 Celsius Degree)
0x55 0xaa 0x11 0x02 0x03 0xFF 0xFF 0x20 (Out of Range)
Function to calculate the temperature:
IF(HightByte>=0xF0)
{
Temperature= ((HightByte-0xF0)*256-LowByte)/10
}
Else
{
Temperature= ((HightByte)*256-LowByte)/10
}
Sensor Connection Diagram
As the sensor uses RS485 interface which can not be connected direclty to the MCU,
a MAX485 chip will bridge the TTL interface to RS485, as shown in Figure 4.
For PC users, either a USB-RS485 or RS232-RS485 converter will bridge the gap. A
diagram is depicted in Figure 5 and 6.