Data Encoding and Scaling

As has been mentioned earlier, an important area of the communication along the

network, that is not defined by the Modbus protocol, is the encoding of numerical data.

A related problem is the adoption of a scaling system for the data once it has been

encoded. (Note: this is an area which requires careful consideration by users of the

MTL838B-MBF.)

There is no problem here for manufacturers who are supplying complete systems,

based on the Modbus network, as they can select a data encoding and scaling system

appropriate to their needs. However, for manufacturers who are supplying products for

general use, there is no possibility that they will be able to determine which data

encoding system will be used by their customers, and they must allow the data

encoding technique to be user selectable.

Three data encoding techniques are the most popular – IEEE, 16-bit unsigned and 16

bit offset.

A further area of difficulty associated with the encoding of data is the way in which the

data is scaled – to provide a resolution of the measured value appropriate to the

requirements of  each application.