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sames

sames

SA2007H

Figure 3: Analog input internal configuration

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SA2007H 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 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.

Referring to the block diagram (figure 1) the SA2007H has two

current sense channels and a voltage sense channel. The

voltage measured is multiplied with the current measured on

the two channels. The multiplied signals from each current

channel is fed to separate power to pulse rate blocks.

The power to pulse rate blocks generate pulses at a frequency

proportional to the instantaneous active power measured.

Pulses on output P1 represent energy measured on current

channel 1. The pulses on output P2 represent energy

measured on current channel 2. Counting the pulses

generated represents the energy measured.

A typical application would be to simultaneous measure

energy/power consumption in both Live and Neutral lines. A

meter tamper condition could be detected when an imbalance

exists between the live and neutral energy/power measured.

Two modes of operation is available on the SA2007H, in one

mode the device is functionally the same as two SA2002H

devices sharing a common voltage channel. Alternatively the

pulse output is latched and an interrupt is generated on any

change of the pulse outputs.

POWER CALCULATION

In Figure 8, the voltage drops across the current transformers

terminating resistors are converted to currents

for each

current sense input, by means of resistors R and R (channel

10

11

1) as well as R and R

(channel 2). The current sense input

12

13.

saturates at an input current of ±25µA peak.

The mains voltage (230VAC) is divided down through a divider

to 14V

. The current into the A/D converter input is set at

RMS

14µA

at nominal mains voltage, via resistor R (1MW).

RMS

7

In this configuration, with a mains voltage of 230V and a

current of 80A, the output frequency measured on P1 or P2 pin

is 1360Hz. In this case the energy associated with a single

pulse is 18.4kW/1360Hz = 13.5Ws per pulse.

ANALOG INPUT CONFIGURATION

The input circuitry of the current and voltage sensor inputs are

illustrated in figure 3. These inputs are protected against

electrostatic discharge through clamping diodes.

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

IV

generate virtual shorts on the signal inputs. Exact duplications

of the input currents are generated for the analog signal

processing circuitry.

ELECTROSTATIC DISCHARGE (ESD)

PROTECTION

The SA2007H integrated circuit's input's/outputs are protected

against ESD.

POWER CONSUMPTION

The power consumption rating of the SA2007H integrated

circuit is less than 30mW.

VOLTAGE

SENSOR

INPUT

IVP

DR-01288

SS

V

CURRENT

SENSOR

INPUTS

IIP

IIN

SS

V

VDD

SS

V

VDD

DD

V

GND

PRELIMINARY