Amp Meter hook up to TIU & 180W

The ammeter goes in series with the power from the transformer, that's correct.  If you have a clamp-on ammeter, you just clamp it around the wire in question.

The number of sidings is not related to the amperage draw.  The amperage draw is determined by the number of loads---locos, cars, accessories---that are actually operating at any given time on a circuit.

Clamp-around amp meter mentioned.

Some of us go for the modern digital models.

On the plus side, it doesn't take batteries, and will measure to 300 amps, but at that point the hair on the back of your hand was usually standing up anyway.   Maybe we should remove the word analog from the dictionary.  Foggy head says probably new 1977.    Additional comment.  While still available, when working with younger participants in the electrical industry, meters with needles and multiple scales appear to be confusing.  The meter pictured was pulled from the trash at the shop a few years ago when several employees refused to use it.  The swing needle multimeter with several scales stacked on top of one another was also considered a throw away. You had to be able to read the correct scale that corresponded to the dial setting.  IMO.   That's not to say those number on the digital screen are correct, but apparently more desirable.  Complication is simplified with a tick tester that simply indicates power present (but it can be deceptive)   Mike    

Thank you all for the responses.  I really appreciate the help that the Forum provides.

Moke Mike