What type of tag would be best to store the rate of speed of a motor?

In the context of storing the rate of speed of a motor, the use of a DINT (Double Integer) tag is not ideal for representing such data, as speed is typically a continuous value that can include fractions. The best choice for capturing a motor's speed would actually involve using a REAL type tag.

The REAL data type can store floating-point numbers, which allows for the representation of decimal values. This is crucial when recording speed, as it often includes fractions (for instance, 123.45 RPM). The ability to represent a wide range of values accurately, including those that aren't whole numbers, makes REAL tags suitable for processes requiring precision, such as motor speed.

In contrast, using a BOOL type (which represents binary states such as true or false) would not provide any meaningful representation of speed. Similarly, a STRING type is designed for text data and wouldn't be capable of storing numerical values in a format that could be used for calculations or comparisons needed in control applications.

Thus, leveraging a REAL tag allows for both the precision and range necessary to accurately monitor and control motor speeds within a Rockwell ControlLogix system.