ADE5166 datasheet(52/148 Pages) AD

52 / 148 page

ADE5166/ADE5169

Current Channel RMS Calculation

Each ADE5166/ADE5169 simultaneously calculates the rms values

for the current and voltage channels in different registers. Figure 57

shows the detail of the signal processing chain for the rms calcula-

tion on the current channel. The current channel rms value is

processed from the samples used in the current channel waveform

sampling mode and is stored in an unsigned 24-bit register (Irms).

One LSB of the current channel rms register is equivalent to 1 LSB

of a current channel waveform sample.

Rev. 0 | Page 52 of 148

The update rate of the current channel rms measurement is

4.096 MHz/5. To minimize noise in the reading of the register, the

Irms register can also be configured to update only with the zero

crossing of the voltage input. This configuration is done by setting

the ZXRMS bit (Bit 2) in the MODE2 register (Address 0x0C).

With the different specified full-scale analog input values, the ADC

produces an output code that is approximately ±0d2,684,354 (see

the Current Channel ADC section). Similarly, the equivalent rms

value of a full-scale ac signal is 0d1,898,124 (0x1CF68C). The cur-

rent rms measurement provided in the ADE5166/ ADE5169 is

accurate to within 0.5% for signal inputs between full scale and

full scale/500. The conversion from the register value to amps

must be done externally in the microprocessor using an amps/LSB

constant.

Current Channel RMS Offset Compensation

The ADE5166/ADE5169 incorporate a current channel rms offset

compensation register (IRMSOS). This is a 12-bit signed register

that can be used to remove offset in the current channel rms

calculation. An offset can exist in the rms calculation due to

input noises that are integrated into the dc component of V2(t).

One LSB of the current channel rms offset is equivalent to

16,384 LSBs of the square of the current channel rms register.

Assuming that the maximum value from the current channel

rms calculation is 0d1,898,124 with full-scale ac inputs, then

1 LSB of the current channel rms offset represents 0.23% of

measurement error at −60 dB down from full scale.

768

IRMSOS

rms

Irms(t)

(4)

where Irms0 is the rms measurement without offset correction.

60Hz

0xD487B0

0x00

IRMSOS[11:0]

Irms[23:0]

226

225

sgn

227

217 216

218

MODE1[5]

HPF

IBGAIN

IPA

IPB

0x2B7850

0x000000

CURRENT CHANNEL

WAVEFORM

DATA RANGE WITH

INTEGRATOR ON (60Hz)

DIGITAL

INTEGRATOR*

CURRENT CHANNEL

WAVEFORM

DATA RANGE WITH

INTEGRATOR OFF

0xD70A3E

0x000000

0x28F5C2

HPF1

LPF3

NOTES:

1. WHEN DIGITAL INTEGRATOR IS ENABLED, FULL-SCALE OUTPUT DATA IS ATTENUATED DEPENDING ON THE SIGNAL

FREQUENCY BECAUSE THE INTEGRATOR HAS A –20dB/DECADE FREQUENCY RESPONSE. WHEN DISABLED, THE

OUTPUT IS NOT FURTHER ATTENUATED.

Figure 57. Current Channel RMS Signal Processing with PGA1 = 2, 4, 8, or 16

VOLTAGE SIGNAL (V(t))

LPF3

LPF1

VOLTAGE CHANNEL

0x28F5C2

VRMSOS[11:0]

0x28F5

0x0

0xD70B

216

sgn

215

27 26

Vrmsx(t)

0x00

Vrmsx[23:0]

|X|

Figure 58. Voltage Channel RMS Signal Processing

ADE5166 数据表(PDF) 52 Page - Analog Devices

ADE5166 数据表(HTML) 52 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载