AS8267 datasheet(25/136 Pages) AMSCO

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Data Sheet AS8267 / AS8268

Revision 1.0, 19-Jun-07

Page 25 of 136

Calibration of V and I Channels

The single channel data may be corrected with a 16-bit calibration value.

The calibration range is [1 LSB; 2 – 1 LSB], step size (1 LSB): 3.052 x 10

-5.

Calibration Register Setting

Value

0000h

0001h

0.00003052 (= 1 LSB)

…

2000h

0.25

…

4000h

0.5

…

8000h

1.0

…

FFFFh

1.99996948 (2 – 1LSB)

The V and I channel RMS calculation and calibration is described below (V and I channel are identical, thus

only the I channel is shown):

The ideal values after RMS calculations of voltage and current are:

RMS_V(ideal) = 479(rms)

RMS_I(ideal) = 292,110(rms)

These values assume ideal input conditions with Vin = 100mVp at rated conditions and Iin = 30mVp (Gain = 20)

at rated conditions.

Due to non-ideal components a different RMS value is calculated: RMS_I(actual). From this, the required

calibration factor is calculated using the following formula:

)

actual

RMS

)

ideal

RMS

cal

The following formula calculates the actual value to be programmed into the calibration registers (cal_v; cal_i1;

cal_i2):

))

768

cal

(

round

(

hex

)

reg

cal

e.g.

RMS_I(ideal) = 292,110 at 40A

10A

73,027

292,110

(ideal)

RMS_I

10A

cal

→

67,185

(actual)

RMS_I

9.2A

actual

→

AS8267 Datasheet(PDF) 25 Page - ams AG

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