CS5480 datasheet(24/70 Pages) CIRRUS

24 / 70 page

CS5480

DS980F3

5.6 Tamper Detection and Correction

In the 1V-1I-1N meter configuration mode, the CS5480

provides flexibility for the user and application program

to adjust the anti-tampering scheme automatically or

manually. Automatic channel selection is enabled by

default. For manual channel selection refer to section

5.6.1.2 Manual Channel Selection on page 25.

The CS5480 provides compensation for at least two

forms of meter tampering — current and voltage tam-

pering.

5.6.1 Anti-tampering on Current

In the 1V-1I-1N mode, current tampering is deterred by

an automatic or manual channel selection scheme. A

dedicated second neutral current input is provided in the

event that the primary current input is impaired by tam-

pering.

5.6.1.1 Automatic Channel Selection

Automatic channel selection is standard in the CS5480.

When tampering is detected, the CS5480 will automatical-

ly select the channel with the greater PxAVG or IxRMS mag-

nitude as the contributor to the total power registers. Using

either PxAVG or IxRMS magnitude depends on the setting

of the IVSP bit in the Config2 register.

To avoid repeated channel transitions at light load, the

Channel Select Minimum Amplitude (PMIN (IRMSMIN))

tion. When either P1AVG (I1RMS) or P2AVG (I2RMS) is

greater than PMIN (IRMSMIN), the CS5480 will enable au-

tomatic channel selection. Within the automatic selection

region, the Channel Select Level (IchanLEVEL) register

sets a minimum difference that will allow an automatic

channel change. The channel select level provides hyster-

esis to prevent repeated channel transitions that would oc-

cur when the primary line current and neutral current are

nearly equal.

Figure 15 shows how the automatic channel selection is

performed. In this figure, the magnitudes of P1AVG and

P2AVG are used for automatic channel selection (IVSP

= 0) and IchanLEVEL = 1.02.

•The P1AVG and P2AVG must meet the Channel

Select Minimum Amplitude (IchanLEVEL). The

highest channel is active, P1AVG in this example.

• Even when the active channel (P1AVG) moves below

the previously lower channel (P2AVG), the channel

selection does not change.

• The new channel selection is only made when the

difference between P1AVG and P2AVG is greater than

2% x P1AVG or P2AVG > P1AVG x IchanLEVEL (1.02).

Channel Select Level

(

Ichan LEVEL)

2% minimum difference

Channel Select Level

(

Ichan LEVEL)

2% minimum difference

Channel Select Minimum Amplitude

PMIN (IRMSMIN)

P1AVG

P2AVG

Channel 1 - Remains Active

Channel 2 - Active

Channel 1 - Active

Automatic Channel

Selection Region

Disabled Automatic Channel

Selection Region

Figure 15. Automatic Channel Selection

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