sames

SA2002P

6/14

http://www.sames.co.za

DR-01283

DIR

V

I

DIR

t

t

t

t

Figure 7: Measured energy direction on DIR

Mains Zero Crossing Indication (FMO)

Figure 6 indicates the behavior of the FMO output relative to the

voltage sense inputs. The square wave signal of FMO indicates

the polarity of the mains voltage. Due to comparator offsets, the

FMO low to high transition can occur within a range as shown in

figure 6. The time between successive low to high transitions

will be equal to the mains voltage period. The FMO output may

be used during calibration.

Signal

Output

Value

Description

DIRO

0

Reverse energy flow

Forward energy flow

1

Direction Indication (DIRO)

The SA2002P provides information about the energy flow

direction on pin DIRO .

A logic 0 on pin DIRO indicates reverse energy flow. Reverse

energy flow is defined as the condition where the voltage

sense input and current sense input are out of phase (greater

than 90 degrees).

Positive energy flow, when voltage sense and both current

sense input are in phase, is indicated on pin DIRO as a logic 1.

The DIRO pin may be used to drive a LED in order to indicate

reverse energy.

Figure 6: Mains zero crossing on FMO

DR-01284

FMO

MAINS

t

V

t

t

Figure 7 shows the behavior of DIR, when energy reversal

takes place. The time period for the DIR signal to change state,

t

, is the time it takes for the internal integrator to count (down)

from its present value to zero. Thus the energy consumption

rate determines the speed of change on DIR.

DIR