According to the BACnet protocol documentation:

Presents the coefficients that are used for converting the pulse signals generated by the measuring instrument into the value displayed by Present_Value. The conversions are performed using integer arithmetic in such a fashion that no measurement-generated pulse signals are lost in the conversion. These coefficients might simply document a conversion performed prior to the reception of the input pulses by the Accumulator object, or they might actually be used by the Accumulator to convert input pulses into the value displayed by Present_Value. Whichever is done is a local matter. This procedure supports non-integral ratios of measurement pulses to Present_Value. For example, in an electrical metering application, the output of the voltage- and current-measuring systems might be 9000/1200 (scale / voltage*current) pulses per kWh, requiring the Accumulator object to accumulate 2/15 kWh/pulse. With this algorithm such pulses can be accurately accumulated and displayed when the units of Present_Value are KILOWATT_HOURS.

Property prescale of object accumulator can be read and written using a block tag with 2 elements.

Text Parameters

Numeric Parameters

Block Elements