The circuit shown on this page is a reasonably Low Cost and moderately Hi-Tech ammeter for use with DCC systems. The circuit meter output is always has the same polarity regardless of the input polarity. This allows a low cost DC voltmeter to be used to monitor a DCC current.
DCC Ammeter Operation
Current Monitor IC 1 produces an output when the current is flowing from terminal A to terminal C.
Current Monitor IC 2 produces an output when the current is flowing from terminal B to terminal D.
The outputs currents from IC2 and IC 2 flow through resistors 5 and 6. Resistor R5 is adjusted so that the voltage shown on the external voltmeter is scaled to the current flowing through resistors R1 and R2. (For example 1 Volt equals 1 Amp.)
For the values given in the schematic; For each 0.1 volts across terminals 2 and 3 of a ZXCT1009 current monitor the output at terminal 1 will produce a current of 1 milliamp. For example: If R1 and R2 are 0.1 ohms and the current through them is 1 amp, the current from the Output terminals of the ZXCT1009 will be 1 milliamp. See the data sheet for more information.
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