Example: Transmit the digital reading in amps and as 4-20 mA from an AC current transformer
Application: Use a 200:5 (200A in, 5A out) AC current transformer. Digitally transmit the AC
current reading in amps with 0.1A resolution. Also transmit a 4-20 mA signal corresponding to
0-100A.
Solution:
• Jumper signal conditioner for 5.000 A current range and AC coupling.
• Under “Input+Display” tab, set “Option Board” to True RMS, Mode to RMS A, Range to
5.0A, “Decimal Point” to dddd.d, and “50/60 Hz Line Freq” to 60 Hz to reject 60 Hz noise.
• Under Scaling tab, if Coordinates is selected, set “High In” to 5.000A and “High Read” to
200.0A. For this application, Coordinates is the easiest, most intuitive scaling method.
• Under Scaling tab, if “Scale, Offset” method is selected, set Scale to 0.4. The reason is that
a 5A full-scale input corresponds to 5,000 input counts, where each input count is
1 mA (as for the 5A scale of a 4-digit meter). These 5,000 input counts need to correspond
to 2,000 output counts, where each output count is 0.1A.
• Under “Analog Out” tab, set Range to “4-20 mA current”, “Lo Range Reading” to 0.0A, and
“Hi Range Reading” to 100.0A.
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