Note: If you are using an NCE Power Cab, it has an Ammeter included, set it up in Cab Parameters. If you are using the Power Cab with an SB3/5, the included Ammeter is not available.
The Bypass Switch: The Bridge Rectifier is necessary to measure the Amps but it reduces the Track Voltage by 1.5 Volts.
If your DCC system has a Voltage Adjustment you can compensate for this 1.5 Volt drop and you can leave out the Bypass Switch.
If your DCC system does NOT have the "adjustment" and you want to operate at the "set" voltage, install the Bypass Switch and operate it in the OPEN position for Current measurements and in the CLOSED position if you don't want to operate with the slightly reduced (1.5 Volt) track Voltage.
See below for measuring the DCC Voltage.
Add the Bridge Rectifier to one of the Track "Power Bus" Feeders as shown below by "hard wiring" the Bridge Rectifier into the Booster Track Terminals or an appropriate location and run 2 wires to the Meter and Switch (if you are using it). Shown below is the " Ammeter Adapter"for my DCC Tool Box, 10 Amp Multimeter, necessary for troubleshooting other layouts or demos etc.
One method of making the "simple" Ammeter using a Jaycar $10 Multimeter and a ZR1314 6.0 Amp Bridge Rectifier with the "D.C." leads soldered into two Banana Plugs for easy removal/install of the Adapter. The two Back leads connect to the "A.C." leads and connect "into" one Track Feeder at the Booster as per the above diagram. You choose the easiest way to make it.
This is all that's necessary to measure the current to the layout.