User's Manual

Operation: C1SD, C1ST, and C1SL Versions
5-22 CENTRON Meter Technical Reference Guide
Demand Calculations
Block Interval Demand
Block demand corresponds to the number of subintervals being equal to one. At
the end of every interval, the microprocessor compares the last completed block
interval demand value to the demand value in memory. If the new value is greater
than the stored value, the new demand value is stored as Maximum Demand. When
a demand reset occurs, maximum demands are reset to zero and the current
interval continues. C1SD will begin a new demand interval. New maximum
demand values are calculated.
Rolling Interval Demand
For rolling interval demand, the programmed number of subintervals make up the
demand interval. At the end of every subinterval, the microprocessor calculates a
demand value based on the last full demand interval. When a demand reset occurs,
all Maximum Demands are reset to zero along with all completed subintervals. The
current subinterval continues (unless C1SD) accumulating data and the new
maximum demand value(s) is (are) calculated for the next subinterval.
Cumulative Demand
When a demand reset is performed, Maximum Demand values are added to the
existing corresponding Cumulative Demand values and written into memory as the
new Cumulative Demand values. These values remain in storage until the next
demand reset.
Continuous Cumulative Demand
Continuous Cumulative Demand is the sum of Maximum and Cumulative Demand
at any time. The calculated interval demand is continuously compared to the
previous Maximum Demand. If this demand is a new peak, it is stored as a
Maximum Demand and adjusts the continuous cumulative register to reflect the
new demand. A demand reset signal clears the Maximum Demand value, but does
not affect the Continuous Cumulative reading.
Previous Interval Demand
Previous interval demand is the calculated demand from the most recently
completed demand interval. When using rolling interval demand, this quantity is
updated after each subinterval. Previous interval demand is not saved in non-
volatile memory. When an interval is completed the demand value is transferred to
the previous interval demand register for display. Upon power up or demand reset,
the previous interval demand register is set to zero and is updated when the first
subinterval is complete.
Present Interval Demand
The present interval demand value is the demand value at the present time
normalized to the demand interval length. Present demand reports the calculated
demand value as it increases from the start of a demand interval to the end of the
interval. For rolling demand intervals, present demand reports the calculated
demand value from the present subinterval as it is accumulating with the previous
set of subintervals.