SONBEST SM2121A Rs232 Interface Liquid Ph Sensor User Manual

SONBEST SM2121A Rs232 Interface Liquid Ph Sensor

SM2121A using the standard,easy access to PLC， DCS and other instruments or systems for monitoring pH state quantities.The internal use of high-precision sensing core and related devices to ensure high reliability and excellent long-term stability can be customizedRS232, RS485,CAN,4-20mA, DC0~5V\10V, ZIGBEE,Lora, WIFI, GPRS and other output methods.

Technical Parameters

Wiring instructions

Any incorrect wiring can cause irreversible damage to the product. Please carefully wire the cable as follows in the case of power failure, and then connect the cable to confirm the correctness and then use it again.

In the case of broken wires, wire the wires as shown in the figure. If the product itself has no leads, the core color is for reference.

Communication Protocol
The product uses RS485 MODBUS-RTU standard protocol format, all operation or reply commands are hexadecimal data. The default device address is 1 when the device is shipped, the default baud rate is 9600, 8, n, 1

Read Data (Function id 0x03)
Inquiry frame (hexadecimal), sending example: Query 1# device 1 data, the host computer sends the

For the correct query frame, the device will respond with data:01 03 02 00 79 79 A6 , the response format is parsed as follows:

Data Description: The data in the command is hexadecimal. Take data 1 as an example. 00 79 is converted to a decimal value of 121. If the data magnification is 100, the actual value is 121/100=1.21. Others and so on.

Data Address Table

read and modify device address Read or query device address
If you don’t know the current device address and there is only one device on the bus, you can use the command FA 03 00 64 00 02 90 5F Query device address.

FA is 250 for the general address. When you don’t know the address, you can use 250 to get the real device address, 00 64 is the device model register.
For the correct query command, the device will respond, for example the response data is: 01 03 02 07 12 3A 79, the format of which is as shown in the following table:

Response should be in the data, the first byte 01 indicates that the real address of the current device is, 55 3C converted to decimal 20182 indicates that the current device main model is 21820, the last two bytes 00 01 Indicates that the device has a status quantity.

Change device address
For example, if the current device address is 1, we want to change to 02, the command is:01 06 00 66 00 02 E8 14 .

After the change is successful, the device will return information: 02 06 00 66 00 02 E8 27 , its format is parsed as shown in the following table:

Response should be in the data, after the modification is successful, the first byte is the new device address. After the general device address is changed, it will take effect immediately. At this time, the user needs to change the query command of the software at the same time.

Read and Modify Baud Rate
Read baud rateThe device default factory baud rate is 9600. If you need to change it, you can change it according to the following table and the corresponding communication protocol. For example, read the current device’s baud rate ID, the command is:01 03 00 67 00 01 35 D5 , its format is parsed as follows.

Read the baud rate encoding of the current device. Baud rate encoding: 1 is 2400; 2 is 4800; 3 is 9600; 4 is 19200; 5 is 38400; 6 is 115200.
For the correct query command, the device will respond, for example the response data is: 01 03 02 00 03 F8 45, the format of which is as shown in the following table:

coded according to baud rate, 03 is 9600, ie the current device has a baud rate of 9600.

Change the baud rate
For example, changing the baud rate from 9600 to 38400, ie changing the code from 3 to 5, the

Change the baud rate from 9600 to 38400, changing the code from 3 to 5. The new baud rate will take effect immediately, at which point the device will lose its response and the baud rate of the device should be queried accordingly. Modified.

Read Correction Value
Read Correction Value When there is an error between the data and the reference standard, we can reduce the display error by adjusting the correction value. The correction difference can be modified to be plus or minus 1000, t hat is, the value range is 0-1000 or 64535 -65535. For example, when the display value is too small, we can correct it by adding 100. The command is: 01 03 00 6B 00 01 F5 D6 . In the command 100 is hex 0x64 If you need to reduce, you can set a negative value, such as -100, corresponding to the hexadecimal value of FF 9C, which is calculated as 100-65535=65435, and then converted to hexadecimal to 0x FF 9C. The correction value starts from 00 6B. We take the first parameter as an example. The correction valu e is read and modified in the same way for multiple parameters.

For the correct query command, the device will respond, for example the response data is: 01 03 02 00 64 B9 AF, the format of which is as shown in the following table:

In the response data, the first byte 01 indicates the real address of the current device, and 00 6B is the first state quantity correction value register. If the device has multiple parameters, other parameters operate in this way. The same, the general temperature, humidity have this parameter, the light generally does not have this item.

Change correction value
For example, the current state quantity is too small, we want to add 1 to its true value, and the current

After the operation is successful, the device will return information: 01 06 00 6B 00 64 F9 FD, the parameters take effect immediately after successful change.

Disclaimer

This document provides all information about the product, does not grant any license to intellectual property, does not express or imply, and prohibits any other means of granting any intellectual property rights, such as the statement of sales terms and conditions of this product, other issues. No liability is assumed. Furthermore, our company makes no warranties, express or implied, regarding the sale and use of this product, including the suitability for the specific use of the product, the marketability or the infringement liability for any patent, copyright or other intellectual property rights, etc. Product specifications and product descriptions may be modified at any time without notice.

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