sames

sames

SA2005M

http://www.sames.co.za

Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)

The current sense inputs connects to a termination resistor

connected across the terminals of a current transformer. At

rated current the resistor values should be selected for input

currents of 16µA

. Referring to figure 8, the resistors R1 and

RMS

R2 on current channel 1, resistors R3 and R4 on current

channel 2 and resistors R5 and R6 on current channel 3, define

the current level into the current sense inputs of the SA2005M.

The current sense inputs saturates at an input current of

±25µA peak. Resistors R29, R30 and R31 are used as current

transformer termination resistors. The voltage drop across the

termination resistors should be at least 20mV at rated

conditions. Values for the current sense inputs are calculated

as follows:

Where:

I = Line current/CT-ratio

L

The value of the termination resistors should be less than the

resistance of the CT's secondary winding.

Voltage Reference Connection (VREF)

A bias resistor of 24kW provides an optimum bias conditions on

chip. Calibration of the SA2005M is done on the voltage sense

inputs as described in the Typical Application.

Rated (RA)

The rated condition select pin allows the metering constants

(LED output and Motor Drive output) to remain unchanged for

different rated conditions having a 1:2:3 scaling ratio, for

example 230V/20A, 230V/40A and 230V/60A. This option

allows for the development of different rated meters requiring

minimal changes. The only changes to be implemented is the

selection of the current sense resistors for the expected rated

load currents and the selection of pins RA, RE and IM.

5/12

RE Pin

Summing Mode

Dividing Ratio

(LED Resolution)

Total sum

Total sum

Absolute sum

Absolute sum

1

4

1

4

VSS

PH/DIR

OPEN

VDD

IM Pin

VSS

PH/DIR

VDD

OPEN

Dividing Ratio (Counter Resolution)

100 (1P/KwH)

10 (10P/KwH)

1 (100P/KwH)

Test Mode

At a rated condition of 230V/60A (13800W), setting the RA pin

to VDD (ratio set to 3/3) and the RE pin to VSS (LED

resolution) the LED pulse rate will be 3200 pulses/KWh. With a

combination of RA, RE and IM settings various rated condition

can easily be met. Refer to the Using the RA, RE, IM inputs

section for further information.

Resolution (RE)

The RE input selects the summing mode for the programmable

adder as well as the dividing ratio for the LED output (LED

resolution). The following table lists the options available:

The summing mode is the representation of the measured

energy and can be either of the following types:

Total sum

This represents the total sum of the energy measured on all

three phases flowing through the current sensors. Negative

energy flow is taken into consideration.

Absolute sum

This represents the sum of the energy measured on all three

phases, regardless of the direction of energy flow through the

current sensors.

Impulses (IM)

The IM inputs selects between 1, 10, or 100 dividing ratio for

the motor drive outputs (counter resolution). Please note that

the device will not perform metering functions while in test

mode. Refer to the Using the RA, Re, Im inputs section for

further information.

Test Inputs (TEST)

The TEST input is the manufacturers test pin and must be

connected to VSS in a metering application.

RA Pin

Rated Conditions Multiplying Ratio

VSS

PH/DIR

VDD

Open

1/3

2/3

3/3

Fast LED output. The output is 1252Hz at rated

current and voltage inputs.