Filter
Top Products
63230-300-212 Appendix B—Using the Command Interface
April 2001 Changing Scale Factors
191
© 2001 Schneider Electric All Rights Reserved
The circuit monitor stores instantaneous metering data in 16-bit single
registers. A value held in each register must be an integer between –32,767
and +32,767. Because some values for metered current, voltage, and power
readings fall outside this range, the circuit monitor uses multipliers, or scale
factors. This enables the circuit monitor to extend the range of metered
values that it can record.
The circuit monitor stores these multipliers as scale factors. A scale factor is
the multiplier expressed as a power of 10. For example, a multiplier of 10 is
represented as a scale factor of 1, since 10
1
=10; a multiplier of 100 is
represented as a scale factor of 2, since 10
2
=100.
You can change the default value of 1 to other values such as 10, 100, or
1,000. However, these scale factors are automatically selected when you set
up the circuit monitor, either from the display or by using
SMS.
If the circuit monitor displays “overflow” for any reading, change the scale
factor to bring the reading back into a range that fits in the register. For
example, because the register cannot store a number as large as 138,000, a
138 kV system requires a multiplier of 10. 138,000 is converted to 13,800 x
10. The circuit monitor stores this value as 13,800 with a scale factor of 1
(because 10
1
=10).
Scale factors are arranged in scale groups. The abbreviated register list in
Appendix A—Abbreviated Register Listing on page 127 shows the scale
group associated with each metered value.
You can use the command interface to change scale factors on a group of
metered values. However, be aware of these important points if you choose
to change scale factors:
Notes:
• We strongly recommend that you do not change the default scale
factors, which are automatically selected by
POWERLOGIC
hardware and
software.
• When using custom software to read circuit monitor data over the
communications link, you must account for these scale factors. To
correctly read any metered value with a scale factor other than 0, multiply
the register value read by the appropriate power of 10.
• As with any change to basic meter setup, when you change a scale factor,
all min/max and peak demand values should be reset.
CHANGING SCALE FACTORS