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sames

sames

SA2007M

Figure 3: Analog input internal configuration

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SA2007M 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. The

SA2007M incorporates an anti-tamper scheme by

continuously measuring the power consumption on both LIVE

and NEUTRAL lines. A fault is indicated when these

measurements differ by more than 12.5%. The SA2007M

generates pulses with a frequency proportional to the larger of

the two current measurements. The source (LIVE or

NEUTRAL) for these pulses is indicated on the SEL1 pin.

Frequency outputs (MOP, MON and LED) are available. The

pulse rate on these pins follows the instantaneous active

power consumption measured.

A low voltage stepper may be driven directly from the device by

connecting it between the MOP and MON pins, alternatively an

impulse counter may be driven directly by connecting it

between MOP and V .

SS

POWER CALCULATION

In Figure 6, 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 1) as

10

11

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

Different pulse rates are available at the MOP and MON pins.

The device may be programmed for a 1 pulse/kWh, 10

pulses/kWh or 100 pulses/kWh output, depending on the

status of the motor pulse rate select pins MP0 and MP1.

The LED pulse rate is fixed at 6400 pulses per kWh. Rated

conditions such as 230V/20A, 230V/40A and 230V/60A may

be chosen with the rated pin. This facility allows meter

manufacturers to cater for a wide range of metering

applications with minimal design changes.

ANALOG INPUT CONFIGURATION

The input circuitry of the current and voltage sensor inputs are

illustrated below.

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 SA2007M integrated circuit's input's/outputs are protected

against ESD.

POWER CONSUMPTION

The power consumption rating of the SA2007M 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