How quickly will the HS Power Meter Module fill the on board memory of an ION 7550/7650 meter?

Issue:
The calculation in this article shows how much time it would take for a High Speed (HS) Power Meter Module to fill 10MB on-board memory of ION 7550/7560. HS Power Meter Module updates their measurement as fast as once per half cycle (rather than once per second) or twice in every cycle.

Resolution:
The assumptions made are as follows:

• On board memory size is 10MB
• Using firmware version 360 or later for the meter
• The meter has only one data recorder module with six inputs (3 phase voltage, 3 phase current)
• No waveform recorder module or event log controller module is in use
• The HS Power Meter Module is updating twice in every cycle
• If we are working on a 60 Hz system, then there will be 120 updates in one second.

Each phase voltage or phase current data takes 5 byte of space and each time stamp takes 8 byte of space.  That is, each update will be 38 byte long (=6X5 byte+8 byte). This 38 byte of memory will be called log.  The total on board memory is 10 MB or 10485760 byte (1MB= 1024 KB, 1 KB= 1024 byte).

Therefore, the on board memory can hold 275941.0526 logs.  In one second there are 120 logs which will fill the entire memory in 2299.508 seconds or in .63875 hour or 38.32500 minute.  Due to this tremendous rate, HS Power Meter Module is only used for recording sub-second events (for example transients) over a very brief period.