© 2008 Siemens Energy & Automation, Inc. All Rights Reserved
PMCM-9340D-0208 ACCESS 9340 and 9360 Meters
2/2008 Appendix B—Using the Command Interface
EN–217
Changing Scale Factors
The meter 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 meter uses
multipliers, or scale factors. This enables the meter to extend the
range of metered values that it can record.
The meter 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 meter, either from the display or by
using WinPM.Net.
If the meter 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 meter 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—Meter Register List on page 119 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:
NOTE:
• We strongly recommend that you do not change the default
scale factors, which are automatically selected by ACCESS
hardware and software.
• When using custom software to read meter 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.
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