ADE7761B

Rev. 0 | Page 20 of 24

Missing Neutral Gain Calibration

Example

When the ADE7761B is in missing neutral mode, the energy is

billed 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

In normal mode, ac voltages of ±330 mV peak are applied to

Channel V1 and Channel V2, and then the expected output

frequency on F1 and F2 is calculated as follows:

Gain

=1; PGA =0

= 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

= 2.5 V (nominal reference value)

Hz

0917

.

0

5

.

2

2

2

Hz

7

.

1

33

.

0

33

.

0

13

.

6

,

2

2

1

=

×

×

×

×

×

=

Frequency

F

F

2

2

1

2

/

1

13

.

6

,

REF

4

1

rms

rms

V

f

MISCAL

V

Gain

Frequency

F

F

−

×

×

×

×

=

(8)

CF Frequency

In missing neutral mode, the ac voltage of ±330 mV peak is

applied to Channel V1, no signal is connected on Channel V2,

and a 330 mV dc input is applied to MISCAL. With the ADE7761B

in the same configuration as the previous example, the expected

output frequencies on CF, F1, and F2 are

where:

Gain

is 1 or 16, depending on the PGA gain selection made

using Logic Input PGA.

is the differential rms voltage signal on Channel V1 (V).

is the differential rms voltage signal on the MISCAL

pin (V).

is the reference voltage (2.5 V ± 8%) (V).

is one of four possible frequencies selected by using Logic

Input S0 and Logic Input S1 (see Table 6).

Hz

0917

.

0

5

.

2

2

Hz

7

.

1

2

/

33

.

0

33

.

0

13

.

6

,

2

=

×

×

×

×

=

Frequency

F

F

2

1

CF Frequency