NCE has an internal supply that reduces the incoming voltage to a track voltage that is adjustable.? If the internal supply were analog than an incoming current meter would be accurate.? It is likely that a switching regulator scheme is used to produce the track voltage.? These supplies are more like constant power devices.? So if the incoming voltage and current were 16 Volts and 5 Amperes and the track voltage was set to 12 Volts than the track current would be 6.7 Amperes.
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If your booster's track voltage is adjustable than measuring the input current would not tell you directly what the output current is.
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Best,
Ken Harstine
Ken Harstine