B&B Electronics RS-485 manual

The step size is also referred to as the resolution. Once the step size is known, all that is needed to determine the voltage of an A/D input is the number of steps. The data returned from the 485SDA10 is the number of steps. The voltage at the A/D inputs can be calculated as follows:

Voltage = (# of steps) * (Step size)

Example 4.1 - Assume: A/D Ref. Input + = 5.0V DC and A/D Ref.Input - = 0V DC.

Therefore:

Reference Range = (A/D Ref. Input +) - (A/D Ref. Input -) Reference Range = (5.0V DC) - (0V DC)

Reference Range = 5.0V DC

Step size = (Reference Range) / 1023 Step size = (5.0V DC) / 1023

Step size = 4.8876 millivolts

Example #1: A/D reading = 1023 (3FFH)

A/D voltage = reading * step size

A/D voltage = 1023 * 4.8876 millivolts

A/D voltage = 5.0 Volts

Example #2: A/D reading = 0

A/D voltage = 0 * 4.8876 millivolts

A/D voltage = 0 Volts

Example #3: A/D reading = 675 (2A3H)

A/D voltage = 675 * 4.8876 millivolts

A/D voltage = 3.2991 Volts

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