4-2
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Section Topics
2308-900-01 Rev. A / July 2008
Section 4: Long Integration Measurements
Model 2308 Portable Device Battery/Charger Simulator User’s Manual
Overview
Long integration is an average current measurement of one or more pulses that can be performed
on either the battery channel (#1) or the charger channel (#2). The integration time can be as long
as 60 seconds. Since long integration is an average measurement, the integration time should be
a complete pulse period or an integral number of pulse periods.
Long integration measurements are accomplished by taking an integral number of integration
cycles during the total measurement time. An integration cycle is the line cycle period (16.67 ms
for 60 Hz) plus a small processing time. The system calculates the number of integration cycles
required based on the total time and rounds down to the nearest integer. Therefore, the actual
measurement time can be slightly less than the requested measurement time by up to one line
cycle time (one cycle is 16.67 ms for 60 Hz and 20 ms for a 50 Hz line frequency. A long
integration reading,
R
1
, is the average of a series of current measurements,
m
i
, defined by:
where
n
is an integer given by:
where:
1
PLC
= one power line cycle
I
t
= integration time
Here the integration time specified by the user and denominator represents the integration time of
1 PLC (16.67 msec for 60 Hz or 20 ms for 50 Hz) and processing overhead. The function int
rounds the argument down to next lowest integer.
Long integration is a technique to extend the capabilities of the power supply A/D circuit beyond its
maximum integration time period. The A/D can measure pulses up to 833 ms. To extend this time
period for longer pulses, the long integration technique uses a filtered and sampled measurement
of the waveform. This gives the power supply the ability to measure signals with periods up to 60
seconds.
The filtering of the waveform adds some restrictions to the types of pulses being measured. If a
pulse train has a high duty cycle, where the off time is less than 200 ms, the first period of the
measured waveform will not have settled to steady state, therefore it will be an inaccurate
measurement. In all cases where the off or low time is less than 200 ms, the filtered pulse will have
reached steady state in the second cycle of the waveform and, therefore, can be accurately
measured (
Figure 4-1
). In other words, to measure a periodic waveform with low times less than
200 ms (high duty cycle), start measurements after the first period occurs. This is not a problem for
one-shot pulses or for pulses with off times greater than 200 ms.
R
1
m
i
k
1
=
n
∑
n
-----------------
=
n
int
I
t
1 PLC
----------------
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