Meters

First of all these meters require a separate power supply...usually a wall wart isolated from the source (voltage or current) you are measuring.

The shunt is how the current is measured. The meter is actually a volt meter that reads a calibrated (tiny) resistance shunt and displays the current in amps. So the shunt is in series with the source you're measuring and doesn't hurt anything. The shunt is usually put next to the common or ground side of the supply being measured.

Chuck is right, do NOT try to run these on a non-isolated power supply.  When I built my track voltage measuring car, I had to use a DC-DC isolation supply to power the meter so I could power it from track voltage.

I have used the volt meters from this same supplier, but not the amp meters. After smoking the first two by not using the 'completely isolated' power supply cjack mentions, the second set worked just fine and are still working. I used them in a voltage car and Gunrunnerjohn pointed me to a completely isolated DC to DC converter the second set worked much better. Volt meters were only a little over $6 each with free shipping though, not a big deal. I see the amp meters are a bit more expensive.

The converter I used for volt meters was a Digi-Key Part #102-2737-ND. I would think it would be ok for powering the amp meters, but they may require something totally different? The ones I had were pretty low current devices as I remember them, but wouldn't think the amp meters would require much more power than the voltage ones?

The meter itself requires very little power, that converter is fine.  You have to remember that converter REQUIRES regulated voltage in, so you need a regulated power supply to feed it, then you use the output to power the meter.

If you're powering it from a wall-wart, no further isolation required, they should be totally isolated.

Thanks you all for the info. I am going to be using PW ZW's and a KW to power my lines and want to measure the voltage and amperage going to each track, I plan on having four separate blocks so I will have four separate meters, one for each block.

  another question comes to mind. Should my circuit breakers be installed before or after the meters? 

I have my circuit breakers before everything, on 180 PoHos. My meters[analog] are connected to the layout master terminal strip[pictured] which sorts out, organizes and distributes the railpower and connected affiliates. 

I agree with Dewey, circuit breakers first.  I like the meters to reflect what's happening at the load, so if the breaker trips, the meter reflects the change.  If you use those DC meters, you can power all of them from one wall-wart if you like, it just has to be isolated from the load leads.

Thank you again for the info I thought the meters would look good as well as functional on the panel but I may just go with the analog because of the price, The Amp meters are very pricey at almost $18.00 a pop. Maybe use the volt meters and analog amp meters to get a smaller panel.

   I have another question about the circuit breakers, I have a few 7 1/2 amp circuit breakers rated for 125vAC/50vDC but they are for 400HZ. Can these be used for my breakers or do I have to go with something rated for 60hz?

Toymaker

If you plan to use AC Analog meters Google "Light Object Meters" for some $10 Toy Train meters. They have a AAC 0-15 amp range meter and a VAC 0-30 volt meter that are in the +[-] 2-1/2% accuracy range. Your pw 275 watt input ZW is capable of 180-190 watts [11-12] amps output which is available at any one throttle or spread over all four throttles depending on how you use it. Therefore a 0-15 amp range amp meter would seem appropriate for each throttle that you plan to use for railpower, "A" and "D" ZW throttles for power districts or "blocks" for example. If you plan to monitor accessory amperage the 3 or 5 AAC meters are more suitable.

Different brand meters in photo but most all require a 2" hole for the barrel.

 Top row Volt Meters showing 18 VAC, bottom row ammeters. Top row right is a VDC Meter monitoring the 12 VDC Tortoise Switch Motor circuit.

If they're thermal breakers as most are, they don't care what the frequency of the current is.

Even DC it seems...

Probably a dumb question, but are there breakers that do care about frequency?

Not to my knowledge.

Some of the electronic stuff might, it's never been an issue, so I never looked into it.  I suspect magnetic actuated breakers do care about both AC/DC and frequency.

This is great info thanks this answers a lot of what I was thinking. I believe I will go with the analog meters.

   I am going to be using 2 post war ZW using the A and D out puts, one for each of my mainlines and one for my small yard, basically using just the outside throttles of each 

ZW, the lines will go from the output of each post  to the circuit breaker, then the Amp meter and Volt meter then on to a buss bar and out to the tracks with a TVS connected to each output ( each out put with its own circuit breaker and set of meters) Does this sound about right.

    I will be using the lionel legacy for control, if I tie all my grounds together can I just connect the legacy unit to any one of the ground post or does it need to be tied to all?

I would connect the Legacy lead to the point of the common that leads to the track or track buss after the meters and breakers.

Carl is right.

But when connecting to pw ZW "U" binding posts you want to be certain all four are tied together internally. Often the wire daisy-chained from post to post is broken on old pw units.

A very common required repair for ZW and KW transformers is the binding posts, not only for the common bus bar, but for the power leads as well.

Carl is right.

But when connecting to pw ZW "U" binding posts you want to be certain all four are tied together internally. Often the wire daisy-chained from post to post is broken on old pw units.

 

A very common required repair for ZW and KW transformers is the binding posts, not only for the common bus bar, but for the power leads as well

Thanks for the info. I ran an ohm meter on the transformers and all the U or common post seem to be connected as they read 0 on the meter but I am not sure how to check the power post on the transformers. They are all putting out 20volts when turned on and throttles up at max ( well the KW only goes to 19.5 but it could be the meter).

   I am thinking of running all the commons to a common terminal and then running from the terminal to the circuit breakers and meters and from there running them to another common terminal, where the legacy will tie in and from there out to the track.

And thank you for the info

Gary

I check the power output by putting a load on the transformer.  I have a bunch of 75W 8 ohm resistors that I combine to get the load I need for testing a transformer.  If you put an 8 ohm load on 20 volts, you are dissipating about 50 watts, that's a nice load to test if there's a problem with the power outputs.

I will have to pick up a few resistors to check the power. I have been looking into terminal strips and came across these

http://www.amazon.com/gp/offer...rs&condition=new

I will be using 14 and 16 AWG stranded copper wire and these looked like they could be convenient for tying in the track feeders 

The Wago's are really nice, they were discussed here a while back and I was impressed with them (not like that means much, but still they are neat). However, I have not tried any yet as I already have a bin full of the Euro style terminal strips. May have to get some Wagos anyway though.