Electrex X3M, Руководство пользователя

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8.6.3 Sampling:
The signals to be measured are sampled with a sampling frequency
c
f
equal to 64 times the network
frequency
f
: shortly, the number of samples per wave is fixed at 64 even with frequency variation.
The sampling is continuous on all waveform. Every 10 wave the samples are passed to the calculation part
and the sampling restart for the next 10 waves.
8.6.4 Grid frequency Measurement:
The minimum measurable frequency is about 38 Hz.
The A/D converter is stopped out of the range 45
÷
65 Hz.
The frequency measurement is taken on phase L1 voltage.
The instrument can measure the fundamental frequency even in presence of very distorted waveforms
and/or very low signal (few Volt).
8.7 Average values and energy Calculation.
8.7.1 Energy counting
X3M is equipped with 8 “non volatile” energy counters which can count up to a maximum of 99999999.9
kWh (either kvarh or kVAh) with a resolution equal to 0.1 kWh (either kvarh or kVAh). The value of these
counters can be read either by communication port or display. When the highest value 99999999.9 is
reached, the counting starts again from zero (roll-over).
8.7.2 Average Powers / maximum demand (m/Max)
X3M has a sliding window integrator which computes the average value of each of the 8 power
measurements on an integration interval that is programmable in the range of 1 through 60 minutes in one
minute steps.
The integration interval slides on the time axis in one minute intervals (when all the values of the
measurements are updated).
The settings of the integration intervals are not memorized when the
instrument is turned off. While the duration of the integration interval may differ from the HOLD period, the
two intervals are both aligned on the minute boundary.
A command can be sent on the communication port
to synchronize the HOLD period (and therefore of the minute boundary of the integration interval) with an
external clock. The maximal value of each of the average power measurements is memorized in a non-
volatile register (maximum demand, MD).
Both the average and maximum demand values are available through the display and the communication
port. A command can be sent (either from the keyboard or the communication port) to reset the maximum
demand values to zero. Another command resets the average power values: it resets the measurements
taken during the last integration interval, but not the measurements taken in the last minute (the step with
which the integration window slides). This preserves the synchronization of the integration interval and of
the HOLD interval on the minute boundary.