EVAL-ADE7756EB Datasheet, PDF (7/15 Pages) Analog Devices – Evaluation Board Documentation AD7756 Energy metering IC

PRELIMINARY TECHNICAL DATA
PRELIMINARY TECHNICAL DATA
EVAL-ADE7756EB
Calibrating the meter
In order to calibrate the energy meter, the line voltage,
test current, line frequency and meter constant are entered
as shown in Figure 8. In this example the line voltage is
entered as 220V, test current is 5A, frequency is 50Hz and
the required meter constant is 3200imp/kWh. With the
parameters entered and the voltage and current circuits
energized, click the calibrate button. The software will
then execute the calibration routine and automatically start
to register energy.
If a HP/AGILENT53131A frequency counter is connected
to a GPIB card of the desktop computer, the software will
automatically read the value of the CF frequency and
process the calibration routine. In this case, the calibration
takes about 5 seconds and the user will be notified when it
is complete.
Otherwise, calibration can be proceeded by changing
CFDIV and APGAIN registers as explained in the
ADE7756 datasheet. The measured CF output frequency
is then adjusted to match the theoretical CF freq. of the
Eval software.
Ensure that the analog input signal levels have been
matched to the transducer output signal levels as described
previously.
Main Selection
In order to access all the internal registers of the
ADE7756 the user must return to the Main Selection
Menu. Figure 9 shows the Main Selection Menu and the
various options. From here such things as phase compen-
sation and Channel 1 and Channel 2 PGA setting can be
made.
To select another option from the menu simply click
on the selection menu. By using the selection menu
the user can read and write the registers of the
ADE7756. This software should be used in conjunc-
tion with the ADE7756 data sheet.
Waveform Sampling Routine
In this mode, the Evaluation Software programs the
ADE7756 for Waveform sampling with an updated
rate of 3.5ksps (CLKIN/1024). The user can define
the number of samples needed and select the Signal
Waveform to transfer. Three parameters are processed
when the waveform is displayed: RMS value, Mean
value and Standard Deviation.
When using this feature with sinewave signals, the
user should be aware that if the samples represent a
non entire number of period of the selected signal
then the RMS and Mean values are biased. To correct
this, the number of samples should be chosen to give
an entire number of signal cycles:
# samples = ^{# signal cycles × ADE 7756 CLKIN Frequency}
1024 × Signal Frequency
Note: If Channel 1 and Channel 2 are at the same
frequency then the signal frequency of the Multiplier
Waveform shoud be chosen as twice the Channel1
Frequency to correct the Signal Processing bias.
On line help
The ADE7756 evaluation software also comes with
on-line help features. In order to activate the help
function goto Help on the Menu Bar and select "Show
Help"—see Figure 10. A Help Window will open. In
order to get a description of a particular option (e.g.,
button, text box etc.) move the cursor over the item of
interest. The Help window will display a description
of the selected item.
Figure 9—Selection Menu & PGA Settings
REV. PrB 01/01
Figure 10—On-line Help Function.
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