Using the ION6200 digital out pulses to verify energy readings can sometimes be found to not be accurate.
Internally, the meter uses a task that operates once a second in order to calculate energy. Thus, once per second the meter looks at the accumulation of energy in the previous second and determines how many pulses are needed for the next second.
What happens if the number of pulses is not a whole number such as 1.2 or .95?
This is where the problem arises. In any one second period we can only pulse an integer number of times. In both cases the meter will wait for the following one second to check. Over a long period of time the ION6200 pulsing will be accurate, but if you look at it for a small number of seconds, it will appear to have lots of errors.
Some basic examples that show the error due to the one second timing are (assuming constant energy of one pulse per second):
- 1 second => 50% maximum error
- 5 seconds => 20% max error
- 10 seconds => 10% max error
- 100 seconds => 1% max error
Thus, obviously the more time the better accuracy. However, even more important than the amount of time is the number of expected pulses. For example, if 1 pulse every 100 seconds is expected and the accuracy of our meter is checked after 200 seconds, there could be up to 50% error. It is suggested that the accuracy be check after a period of time that allows for a large number of expected pulses (100/1000 pulses should be enough).
: This also explains why a constant energy source can have variable time between pulses.