SA9604A

sames

10/20

represents the active power, reactive power and voltage integrated over time. The

increase of decrease between readings is the energy consumption. The registers

are not affected during access. No error is possible during read, because all control

signals are generated on chip. The registers can be accessed in any sequence at

any time without problems.

The voltage sense zero crossing is a 1mS pulse available on FM150, (Pin 7). This

information allows a supervisor (ie: microcontroller) to monitor when the next read

operation should be performed. The FM150 output is only suitable if all phase

voltages are connected. Should one or more phases fail the FM150 output becomes

unstable. A better approach would be to monitor the upper bits of the frequency

register (18, 19). A measurement cycle is completed when these bits change to the

same state again (00..00 or 01..01 or 10..10 or 11..11).