Product

Technical parameter	Parameter value
Noise range	30~130dB
Noise accuracy	±3%
Interface	RS485/TTL/DC0-3V
Power	DC5V 1A
Running temperature	-30~80℃
Working humidity	5%RH~90%RH

Product Selection

    Product DesignRS485,TTL,DC0-3VMultiple output methods, the products are divided into the following models depending on the output method.

Product model	output method
YN7902B	RS485总线
YN7902TTL	TTL

Product Size

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How to use?

Application solution

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Communication Protocol

    The product uses the RS485 MODBUS-RTU standard protocol format, and all operation or reply commands are in hexadecimal data. When the device leaves the factory, the default device address is 1, and the default baud rate is: for modules and non-recording instruments: 9600, 8, n, 1 (for the recorder series products, the default is: 115200, 8, n, 1).
1. Read data (Function code 0x03)
    The inquiry frame (in hexadecimal). Example of sending: To query 1 piece of data of device No. 1, the host computer sends the command: 01 03 00 00 00 01 84 0A .

Address	Function code	Starting address	Data length	Checksum
01	03	00 00	00 01	84 0A

    For a correct inquiry frame, the device will respond with data: 01 03 02 02 18 B9 2E , and the response format is:

Address	Function code	Length	Data 1	Checksum
01	03	02	02 18	B9 2E

    Data description: The data in the command is in hexadecimal. Taking Data 1 as an example, 02 18 converted to decimal value is 536. Assuming the data magnification factor is 10, then the true value is 536/10 = 53.6, and the others can be deduced by analogy.
2. Common Data Address Table

Configuration Address	Register Address	Register Description	Data Type	Value Range
40001	00 00	noise	Read Only	0~65535
40101	00 64	Model Code	Read-only	0~59999
40102	00 65	Total Number of Measuring Points	Read-only	1~1600
40103	00 66	Device Address	Read/Write	1~249
40104	00 67	Baud Rate	Read/Write	0~6
40105	00 68	Communication Mode	Read/Write	1 Query
2 Active Upload	40106	00 69	Protocol Type	Read/Write
1 MODBUS-RTU	Others Unused

  For example, the range is 30~130dB, the analog output is 0~3V DC0-3Vvoltage signal, noise and DC0-3Vvoltage The calculation relationship is as shown in the formula: C = (A2-A1) * (X-B1) / (B2-B1) + A1, where A2 is noise range upper limit, A1 is the lower limit of the range, B2 is DC0-3Vvoltage output range upper limit, B1 is the lower limit, X is the currently read noise value, and C is the calculated DC0-3Vvoltage value. The list of commonly used values is as follows:

DC0-3Vvoltage(V)	noiseValue (dB)	Calculation Process
0	30.0	(130-30)*(0-0)÷(3-0)+30
1	63.3	(130-30)*(1-0)÷(3-0)+30
2	96.7	(130-30)*(2-0)÷(3-0)+30
3	130.0	(130-30)*(3-0)÷(3-0)+30

    As shown in the above formula, when measuring 1.5V, current DC0-3Vvoltage is 50dB。