Line Input Voltage - How to interpret Logs

[Anonymous user]

I am looking at the Data Logs on my SC620 and interpreting what I see for the maximum and minimum Line Input Voltage over an extended logging period. The values listed in this log seem to be selected from a list of possible values at discrete intervals of about 1.4 to 1.5 volts. Am I interpreting things correctly with the following?

The logged maximum voltage value is the threshold voltage which was not exceeded for more than a negligible amount of time during the set logging interval leading up to value.

I am also using a calibrated multimeter to do spot measurements during the logging period as a reference check. Any further information on this topic would be very helpful at this stage.

[voidstar_apc]

Big picture -- any notion of "max" or "min" voltage is subject to bandwidth constraints, otherwise it would just be measuring noise on the line.

In the case of the SmartUPS, the network management card samples the line voltage on the order of seconds and you're seeing the max or min of that. Good for observing long term voltage behaviors but you won't see transients. Newer UPSes don't even report max and min.

[Anonymous user]

Thank you voidstar for your feedback.  I do not have a network management card in my ups, just a serial interface.  I don’t know if that uses a different monitoring model.

I am looking at a monitoring session that ran for 11 days logging at 1 minute intervals.  So that is about 16,000 records.  What I can see is that all the voltage levels recorded are drawn from just eight voltage values, namely:

250.5
249.1
247.6
244.8
243.3
240.4
239.0
237.6

There are no intermediate voltages tabled for either Minimum Line Voltage or Maximum Line Voltage.  I can only conclude that the monitoring system is only acknowledging the tightest band of voltages for each sampling interval with the band limits drawn from the eight values given above.

For some logged intervals the maximum voltage and minimum voltage are the same.   You could conclude from this that there was insufficient transients/noise present during that interval to justify logging the next highest or lowest reference voltage.  This is just surmising on my part.  What I would really like to know is the model the monitoring system is using to discretize the recorded values.

[Anonymous user]

Do I need to conclude that the rationale for the method of voltage measurement on my SC620 is secret APC business?

[voidstar_apc · Accepted solution]

I don't think there's published information about low-level details of that nature. It's reasonable to assume there's quantization from A/D conversion, processing, and binary to decimal conversion.

You might find a variac useful. I use it when testing UPS transfer behavior. It lets you set the voltage and see what happens.