63230-300-212 AppendixB—Using the Command Interface
April 2001 Changing Scale Factors
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© 2001 Schneider Electric All Rights Reserved
The circuit monitorstores instantaneous metering data in 16-bit single
registers.A value held in each registermust be an integer between –32,767
and +32,767.Because some values for metered current, voltage, and power
readings falloutside this range, the circuit monitor uses multipliers,or scale
factors.This enables the circuit monitor to extend the rangeof metered
values thatit can record.
The circuitmonitor stores these multipliers as scale factors.A scale factor is
the multiplierexpressed as a power of 10. For example,a multiplier of 10 is
representedas a scalefactor of 1, since 101=10; a multiplier of 100 is
representedas a scalefactor of 2, since 102=100.
Youcan change the default value of 1 to other valuessuch as 10, 100, or
1,000. However,these scalefactors are automatically selectedwhen you set
up the circuit monitor,either from the display or by using SMS.
If the circuitmonitor displays “overflow”forany reading, change the scale
factorto bring the reading back into a range that fits in the register.For
example,because the register cannot store a number as largeas 138,000, a
138 kV system requiresa multiplier of 10. 138,000 is converted to 13,800 x
10. The circuit monitorstores this value as 13,800 with a scale factor of 1
(because 101=10).
Scale factorsare arranged in scale groups. The abbreviated registerlist in
AppendixA—Abbreviated Register Listing on page 127 shows the scale
group associatedwith each metered value.
Youcan use the command interface to change scale factorson a group of
metered values.However, be awareof these important points if you choose
to change scale factors:
Notes:
•We stronglyrecommend that you do not change the default scale
factors,which are automatically selected byPOWERLOGIC hardware and
software.
•When using custom softwareto read circuit monitor data over the
communicationslink, you must account for these scale factors.To
correctlyread any metered value with a scale factorother than 0, multiply
the register valueread by the appropriate power of 10.
•Aswi thany change to basic meter setup, when you changea scale factor,
all min/max and peakdemand values should be reset.
CHANGING SCALE FACTORS