FS7755

Rev. 1.1

20/22

designing an energy meter, the nominal design voltage on Channel 2 (voltage) should be set to half scale

to allow for calibration of the meter constant. The current channel should also be no more than half scale

when the meter sees maximum load. This will allow over current signals and signals with high crest factors

to be accommodated. Table Ⅵ shows the output frequency on F1 and F2 when both analog inputs are half

scale. The frequencies listed in Table Ⅵ align very well with those listed in TableⅤ for maximum load.

S1 S0

(Hz)

Frequency on F1 and F2 (Hz)

(Ch1 and Ch2 Half Scale AC Inputs)

0

0

1.7

0.085

0

1

3.4

0.17

1

0

6.8

0.34

1

1 13.6

0.68

Table Ⅵ F1 and F2 Frequency with Half Scale AC Inputs

with a meter constant of 100imp/kWhr should be compared with Column 4 of Table Ⅵ. The frequency that is

maximum current of 25A is being designed, the output frequency on F1 and F2 with a meter constant of

100imp/kWhr is 0.153Hz at 25A and 220V (from Table Ⅴ). Looking at Table Ⅵ, the closest frequency to

0.153Hz in column four is 0.17Hz. Therefore, F2 (3.4Hz—see Table II) is selected for this design.