The Modbus Data Does Not Match What Is On The Screen. What Is Wrong?

1.	The Modbus Data Does Not Match What Is On The Screen. What Is Wrong?
Answer» The addressing may be off by one depending upon how the host software handles addressing. Slow communications may delay updates on MODBUS data. Host software is not configured to continually poll for new readings. The data format may be set up incorrectly. Refer to the user manual’s MODBUS table for the data formatting. TYPICALLY the data will be in binary/decimal format. In certain situations the data may be in hexadecimal. Some data has implied decimal places so that a value of 432.1 will be 4321 in MODBUS. Some large numbers may require two addresses. This is called a double word. The low address (word) will CONTAIN the first four places while the higher address (word) will contain the upper four digits. For a quick conversion take the (high word X 10000) + low word. SOMETIMES scaling is required to derive the proper NUMBER. The scaling is indicated on the MODBUS table where the ACTUAL data is given and then the scale value. For example, if the actual reading is from 0 to 4095 and the scaling is from 0 to 100 then the actual value will have to be divided by 40.95 to get the proper scaling.

Answer»

The addressing may be off by one depending upon how the host software handles addressing.
Slow communications may delay updates on MODBUS data.
Host software is not configured to continually poll for new readings.
The data format may be set up incorrectly. Refer to the user manual’s MODBUS table for the data formatting.
TYPICALLY the data will be in binary/decimal format. In certain situations the data may be in hexadecimal.
Some data has implied decimal places so that a value of 432.1 will be 4321 in MODBUS.
Some large numbers may require two addresses. This is called a double word. The low address (word) will CONTAIN the first four places while the higher address (word) will contain the upper four digits. For a quick conversion take the (high word X 10000) + low word.
SOMETIMES scaling is required to derive the proper NUMBER. The scaling is indicated on the MODBUS table where the ACTUAL data is given and then the scale value. For example, if the actual reading is from 0 to 4095 and the scaling is from 0 to 100 then the actual value will have to be divided by 40.95 to get the proper scaling.

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