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sames

SA2002D

http://www.sames.co.za

Figure 4: Analog Input Internal Configuration

FUNCTIONAL DESCRIPTION

The SA2002D is a CMOS mixed signal Analog/Digital

integrated circuit, which performs power/energy calculations

across a power range of 1000:1, to an overall accuracy of

better than Class 1.

The integrated circuit includes all the required functions for 1-

phase power and energy measurement such as two

oversampling A/D converters for the voltage and current sense

inputs, power calculation and energy integration. Internal

offsets are eliminated through the use of cancellation

procedures. The SA2002D generates pulses, the frequency of

which is proportional to the power consumption. A

complementary output (MOP and MON) is provided for the

stepper motor. One energy pulse is represented by MOP pulse

and subsequently followed by a MON pulse. This configuration

avoids the possibility that, after power up, the first energy pulse

is lost due to the stepper motor being in the wrong phase. The

pulse rate on these pins follow the instantaneous active power

consumption. The LED pulse output follows the average power

consumption measured and is intended for calibration

proposes.

POWER CALCULATION

In the Application Circuit (Figure 3), the voltage drops across

the shunt will be between 0 and 16mV

(0 to 80A through a

shunt resistor of 200

he voltage is converted to a current

of between 0 and 16mV

, by means of resistors R1 and R2.

The current sense input saturates at an input current

RMS

RMS

µ). T

of ±25µA

peak.

For the voltage sensor input, the mains voltage (230VAC) is

W

VOLTAGE

SENSOR

INPUT

IVP

DR-01288

SS

V

CURRENT

SENSOR

INPUTS

IIP

IIN

SS

V

VDD

SS

V

VDD

DD

V

GND

VDD

VDD

Supply

Supply

N

L

PULSES

REVERSE

VDD

IIN

R1

R2

R5

R3

R4

P1

IIP

IVP

AGND

VSS TEST R0 R1 R2

VREF

LOAD

DR-01568

L

N

LED

MOP

SA2002

8888888

MON

DIRO DIRI

Figure 3: Application Circuit

*The figure not in parenthesis indicates that a MOP pulse

followed by a MON pulse is treated as one energy pulse. The

figure inside parenthesis means that a MOP pulse followed by

a MON pulse is treated as two energy pulses.

divided down through a divider (R3, R4 and P1) to

. The

current into the A/D converter input is set at

at nominal

mains voltage, via resistor R5 (1M

P1 may be varied for

calibration purposes.

The pulse rate available at the motor drive pins MOP and MON

(counter resolution) is fixed at 100 (200) impulses/kWh*. The

frequency of the LED pin is dependant on the settings of pins

R0, R1 and R2, which allow a selection of different rated

conditions. In this case (R0, R1 and R2 set to logic 0) the LED

output is 6400 impulses/kWh, with the rated conditions set to

220V/10A. This facility allows meter manufacturers to cater for

a wide range of metering applications with minimal design

changes.

The feedback loops from the outputs of the amplifiers A and A

generate virtual shorts on the signal inputs. Exact duplications

of the input currents are generated for the analog signal

processing circuitry.

14V

14µA

The input circuitry of the current and voltage sensor inputs is

illustrated in figure 3.

These inputs are protected against electrostatic discharge

through clamping diodes.

RMS

RMS

IV

W).

ANALOG INPUT CONFIGURATION