sames

PM2102DPD

7/16

http://www.sames.co.za

PRELIMINARY

Table 4: Different meter constants

R2

R1

R0

Rated

Condition

(V / I)

LED

Output

(p/kWh)

MON,

MOP

(p/kWh)

0

0

0

220/10A

6400

100

0

0

1

220/20A

3200

100

0

1

0

220/40A

1600

100

0

1

1

220/80A

800

100

1

0

0

220/6A

6400

100

1

0

1

220/30A

3200

100

1

1

0

220/60A

1600

100

The compensating capacitor C7 is calculated next for a phase

shift of 0.18 degrees.

Use a standard value 1µF non-polar electrolytic capacitor with

a working voltage of at least 16V.

The pulse constant is derived from the equation below:

Therefore from table 3, R0 = 0, R1 = 1, and R2 = 0.

The following table list the most common and frequently used

pulse and motor constants for different rated conditions. This

is an easy reference for meter manufacturers, and the

constants not listed can be calculated from

the equations

provided in the previous examples.

C = 1/ (2 x x mains frequency x R12 x tan (Phase shift angle))

C = 1/ (2 x x 50 x 1M x tan (0.18 degrees))

C = 1.013µF

LED p/kWh =

1160p/sec x (1 / DF_LED) x [3600/((Vnom x

Imax)/1000)]

=

1160 p/sec x (1 / DF_LED) x[3600 / (220 x

40) / 1000]

1600 =

1160 p/sec x (1 / DF_LED ) x 409.0

1 / DF_LED =

0.003372

DF_LED =

296

MOTOR p/kWh = LED p/kWh / DF_MO

100 = 1600 / DF_MO

DF_MO= 16

p

p

Standard meter constants for various rated conditions

Module Calibration

PCB Design considerations

Power supply

The output frequency can be adjusted and calibrated by means

of the variable resistor P1 connected in the voltage divider as

shown in figure 3 on page 3.

These are a number of aspects to consider when designing a

PCB for a power/energy meter application. Only a few of the

more critical aspects are discussed here.

The sense resistors on the current input, R6 and R7 must be

located as close to the SA2102D-input pins as possible. This

also holds true for the 1M

resistor (R12), and the biasing

resistor R13. Also note that the supply bypass capacitors C1,

C2 and C6 must be positioned as close as possible to the

supply pins of the SA2102D, and connected to a solid ground

plane.

It is advisable to keep the ground plane surrounding the device

clear of noise that may influence the sensing signals.

The module is protected from high transients on the mains

voltage input by means of a Metal Oxide Varistor. The MOV will

clamp high transients with a sufficiently long rise time, hence

protecting the PCB.

The onboard power supply consists of a simple capacitive

divider to deliver the output voltage that is rectified by a diode

pair, and held constant by means of two TL431 regulators.

The maximum current available from the power supply is

approximately 20mA.

Please take note that the module is fitted with a 470nF/250VAC

X3 type capacitor for 220VAC mains supply. This capacitor

must be changed to 1µF/150VAC X3 type when the mains

supply voltage is changed to a 110VAC network.

W