BL0921

BL0921

BL0921

BL0921

http://www.belling.com.cn

- 12 -

3/15/2007

Total 13 Pages

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

low-pass filters this product to extract real power information. This real power information is then

converted to a frequency. The frequency information is output on F1 and F2 in the form of active

low pulses. The pulse rate at these outputs is relatively low. It means that the frequency at these

outputs is generated from real power information accumulated over a relatively long period of

time. The result is an output frequency that is proportional to the average real power. The average

of the real power signal is implicit to the digital-to-frequency conversion. The output frequency or

pulse rate is related to the input voltage signals by the following equation.

2

)

(

)

(

5

.

3

REF

V

Fz

Gain

i

V

v

V

Freq

×

×

×

×

=

Freq——Output frequency on F1 and F2 (Hz)

V(v)——Differential rms voltage signal on Channel 1 (volts)

V(i)——Differential rms voltage signal on Channel 2 (volts)

Gain——1 , 16 depending on the PGA gain selection, using logic inputs G

Vref——The reference voltage (2.4 V±8%) (volts)

Fz——One of four possible frequencies selected by using the logic inputs S0 and S1.

S1

S0

Fz(Hz)

0

0

1.7

0

1

3.4

1

0

6.8

1

1

13.6

Frequency Output CF

The pulse output CF (Calibration Frequency) is intended for use during calibration. The output

pulse rate on CF can be up to 128 times the pulse rate on F1 and F2. The following Table shows

how the two frequencies are related, depending on the states of the logic inputs S0, S1 and SCF.

Mode

S1

S0

CF/F1 (or F2)

1

0

0

64

2

0

1

32

3

1

0

16

4

1

1

8

Because of its relatively high pulse rate, the frequency at this logic output is proportional to the

instantaneous real power. As is the case with F1 and F2, the frequency is derived from the output

of the low-pass filter after multiplication. However, because the output frequency is high, this real

power information is accumulated over a much shorter time. Hence less averaging is carried out in

the digital-to-frequency conversion. With much less averaging of the real power signal, the CF

output is much more responsive to power fluctuations.

Gain Selection

By select the digital input G0 and G1 voltage (5V or 0V), we can adjust the gain of current