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sames

SA2102D

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SA2102D is a CMOS integrated circuit, which performs

power/energy calculations across a dynamic range of 1000:1

to an accuracy that exceeds the IEC 61036 Class 1

specification.

The integrated circuit includes all the required functions for

single phase power and energy measurement. Two A/D

converters sample the voltage and current inputs. The

calculations required for power and energy are performed and

pulses on the LED, MON and MOP outputs represent the

results.

Internal offsets are eliminated through the use of cancellation

techniques. The SA2102D generates pulses at a frequency

that is proportional to the power consumption. Complimentary

output pins MOP and MON are provided for driving a stepper

motor. A MOP pulse followed immediately by a MON pulse

represents an energy pulse. This minimizes the risk of (after

power up) losing the first energy pulse as a result of the stepper

motor residing in the wrong phase.

The LED output is normally proportional to the average power

consumption measured. When in FAST mode, the LED output

is proportional to the instantaneous active power consumption.

The FAST mode is intended for meter calibration purposes.

The two A/D converters convert the signals on the voltage and

current sense inputs to a digital format for further processing.

The current sense inputs (IIP and IIN) are identical and

balanced. A input signal with a range of 1:1000 is measured at

these inputs.

An integrated anti-creep function prevents any output pulses if

the measured power is less than 0.02% of the meters rated

current.

The two digital signals, accurately representing the current and

voltage inputs, are multiplied using digital multiplication. The

output of the multiplier is the instantaneous power.

For voltage and current in phase instantaneous power is

calculated by:

Instantaneous power

let

,

,

p(t)

=

=

p(t)

=

=

=

where

v(t) is the instantaneous voltage

i(t) is the instantaneous current,

V is the maximum amplitude of the voltage signal,

I is the maximum amplitude of the current signal,

is the voltage phase angle,

is the current phase angle and

on a 50Hz mains system.

p(t)

M

M

= 100Hz noise component

This power information is then integrated over time to provide

the average power information.

Average Power (P)

=

=

Where

is the instantaneous power and

cos

is the power factor.

ANALOG INPUT CONFIGURATION

The input circuitry of the current and voltage sensor inputs is

illustrated in figure 5.

GND

VDD

DR-01148

VOLTAGE

SENSOR

INPUT

IVP

SS

V

IIN

IIP

CURRENT

SENSOR

INPUTS

SS

V

SS

V

VDD

DD

V

Figure 5: Analog input configuration

)

(

)

(

t

i

t

v

´

q

y

t

d

t

p

T

T

ò

0

)

(

1

)

sin(

)

sin(

y

w

q

w+

´

+

t

I

t

V

M

M

y

q

j-

=

2

M

RMS

V

V

=

2

M

RMS

I

I

=

)

sin(

)

sin(

y

w

q

w+

+

t

t

I

V

M

M

)

sin(

)

sin(

j

q

w

q

w-

+

+

t

t

I

V

M

M

)]

)

(

2

cos(

[cos

j

q

w

j-

+

-

t

I

V

RMS

RMS

)

)

(

2

cos(

j

q

w-

+

t

VI

j

cos

RMS

V

j