Demand Measurements - Bitronics M350 User Manual

sample is corrected for gain using factory calibration values stored in non-volatile
memory on the board. Additionally, a continuous DC removal is performed on all
inputs.
The advantages of this method of voltage measurement are apparent when the M350
V3 is used on the common 2, 2½, and 3 element systems (refer to Section 6.5). The
M350 V3 is always calculating Line-to-Neutral, and Line-to-Line voltages with equal
accuracy. On 2 element connections, any phase can serve as the reference phase.
On 2½ element systems, one of the phase-to-neutral voltages is missing, and the
M350 V3 must create it from the vector sum of the other two phase-to-neutral
voltages. In order to configure the M350 V3 for 2½ element mode and which phase
voltage is missing, select one of the following: 2.5 element - A, 2.5 element - B, or 2.5
element – C.

6.4 Demand Measurements

The traditional thermal demand meter displays a value that represents the logarithmic
response of a heating element in the instrument driven by the applied signal. The
most positive value since the last instrument reset is known as the maximum demand
(or peak demand) and the lowest value since the last instrument reset is known as the
minimum demand. Since thermal demand is a heating and cooling phenomenon, the
demand value has a response time T, defined as the time for the demand function to
change 90% of the difference between the applied signal and the initial demand value.
For utility applications, the traditional value of T is 15 minutes, although the M350 can
accommodate other demand intervals (Section 6.4.4).
The M350 generates a demand value using modern microprocessor technology in
place of heating and cooling circuits, it is therefore much more accurate and
repeatable over a wide range of input values. In operation, the M350 continuously
samples the basic measured quantities, and digitally integrates the samples with a
time constant T to obtain the demand value. The calculated demand value is
continuously checked against the previous maximum and minimum demand values.
This process continues indefinitely, until the demand is reset or until the meter is reset
(or power removed and reapplied). The demand reset and power-up algorithms are
different for each measurement. These routines are further described in following
paragraphs. The maximum and minimum demand values are stored in non-volatile
memory on the Host Processor module.
NOTE: Changing VT or CT ratios does NOT reset demand measurements to
zero.
Meter Type Demand Quantity
M350 A3 Amperes
ML0038 September 27, 2017
Phase Reference
Phase
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Copyright 2017 Bitronics, LLC
Function
Present, Max