ADE7761A
Missing Neutral Gain Calibration
Example
When the ADE7761A is in missing neutral mode, the energy is
bill based on the active current input signal level. The frequency
outputs in this mode can be calibrated with the MISCAL analog
input pin. In this mode, applying a dc voltage of 330 mV on
MISCAL is equivalent to applying, in normal mode, a pure sine
wave on the voltage input with a peak value of 330 mV. The
MISCAL input can vary from 0 V to 660 mV (see the Analog
Inputs section). When set to 0 V, the frequency outputs are
close to zero. When set to 660 mV dc, the frequency outputs are
twice that when MISCAL is at 330 mV dc. In other words,
Equation 7 can be used in missing neutral mode by replacing
V2rms by MISCALrms /√2.
In normal mode, ac voltages of 330 mV peak are applied to V1
and V2, and then the expected output frequency on F1 and F2 is
calculated as:
Gain =1 ; PGA =0
F1–4 = 1.7 Hz, SCF = S1 = S0 = 0
V1 = rms of 330 mV peak ac = 0.33/√2 V
V2 = rms of 330 mV peak ac = 0.33/√2 V
VREF = 2.5 V (nominal reference value)
5.70×0.33×0.33×1.7Hz
F , F2 Frequency =
F , F2 Frequency =
= 0.084Hz
1
1
2 × 2 ×2.52
(8)
5.70×Gain×V1rms × MISCALrms / 2 ×F
1−4
CF Frequency = F1 − F2 Frequency × 64 = 5.4 Hz
2
VREF
In missing neutral mode, the ac voltage of 330 mV peak is
applied to V1, no signal is connected on V2, and a 330 mV dc
input is applied to MISCAL. With the ADE7761A in the same
configuration as the previous example, the expected output
frequencies on CF, F1, and F2 are
where:
F1, F2 Frequency is the output frequency on F1 and F2 (Hz).
V1rms is the differential rms voltage signal on Channel 1 (V).
MISCALrms is the differential rms voltage signal on the MISCAL
pin (V).
5.70×0.33×0.33/ 2 ×1.7Hz
F1,F2 Frequency =
= 0.084Hz
2 × 2.52
Gain is 1 or 16, depending on the PGA gain selection made
using logic input PGA.
CF Frequency = F1, F2 Frequency × 64 = 5.4 Hz
V
REF is the reference voltage (2.5 V 8%) (V).
1-4 is one of four possible frequencies selected by using the
logic inputs S0 and S1 (see Table 6).
F
Rev. 0 | Page 20 of 24
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