Got a new transformer in an e-bay grab bag and want to know how to test the outlets on a multimeter. First off, what setting to use as I have one with many settings. Next what should it read on the variable DC and on the AC outlet.
when using a meter and your not sure of the range, start with the highest and adjust until you get a reading in range. Aligator or clip leads might be helpful. you might be able to trap a probe behind the screw terminal. trapping just one probe while holding the other against the other terminal would be helpful.
the output voltages are usually indicated somewhere on the unit. If not the AC output is probably between 10-20 V. Set the meter to an AC scale that is greater than that range to start. Adjust the scale lower if you see something thats low.
the DC output should also be max in that range. Most likely around 12 V. Set the meter to a DC scale in that range. The meter should vary between zero and the max voltage when you adjust the throttle.
greg - Philadelphia & Reading / Reading
A Transformer is always AC. A Power Supply can be AC or DC. Wall Warts are usually marked.
LION connects the inputs of the meter to the outputs of the transformer.
Him Then throws out the meter and buys a new one.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
BroadwayLion A Transformer is always AC. A Power Supply can be AC or DC. Wall Warts are usually marked. LION connects the inputs of the meter to the outputs of the transformer. Him Then throws out the meter and buys a new one. ROAR
Let's assume what you've got is REALLY a transformer (see previous posters).
If so, it MAY have writing on it. This may say many things. In particular, it would be nice if it said the input and output voltages and which terminals were which. Obviously, you're missing some or all of that or you wouldn't be asking. I think.
You can tell the input and output terminals apart by measuring the resistance of the coils. Find the two terminals across which is the highest resistance (highest because the coil wire size is smaller--lower current). This is the input side. The remaining two are the output side. You may now apply an input voltage and read the output voltage using your AC scale.
The previous paragraph assumes you want to step down a voltage. It should be noted that sometimes a person will want to go in the opposite direction--to step UP the voltage. That also will work.
There is one other thing of import: The maximum voltage on the system. You will note that the input/output coils will have a ratio of reduction or increase. So you might put 120V in and get 12V out. But you can also put in 12,000V and get 1200V out. Or 12V in and 1.2V out. What's critical here is the MAXIMUM voltage that can be applied before the insulation fails.......
I include the previous paragraph because there are many kinds of transformers. And, since yours is apparently unlabeled, you're missing some important data.
Ed
With so little info and no picture of the transformer, pay close attention to what you have been told. You have to know first, what is the primary winding before attaching 120VAC.
Your question leaves us thinking you have not idea about transformers or working with mains power.
This link might help you a little about using a meter. There are many more sites that will show how to use meters when searching.
http://tinyurl.com/h5dwurv
Information overload. lol
https://en.wikipedia.org/wiki/Transformer
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
at left below, an AC transformer
at right below, an Ebay listing for a model railroad transformer (and ratings)
Hey, you are making this way more complex than needed. All I wanted was set the meter to xxx for dc and yyy for ac. This is a transformer made for model railroading, just wanted to test it and know what settings to use instead of guessing as in the past. I know which output is which and what its output is soposed to be.
Nomenclature: A transformer is a magnetic device than changes the voltage of AC current only. The AC powered trains like Lionel use transformers to step the 110 volt house current down to something safe to put on the rails, and give control of track voltage. DC powered trains like American HO, use a power pack, a device containing a transformer to step down the 110 volt house current, AND a rectifier to make the low voltage AC into DC, AND a throttle to control the output voltage.
Assuming the device you bought is a power pack, it ought to have two terminals for variable DC output (track power) that go from a volt or so to 12 volts and perhaps a bit more as the throttle is run from min to max. And it ought to have two terminals for fixed voltage (structure lights, switch machines, and the like) providing maybe 16 volts AC.
Your multimeter will have a range switch with selections of DC volts, AC volts, Ohms, and current (mA or Amps). Basic rule, never connect a live voltage source to the ohms or current range of any meter. It will damage the meter. For safety, always set the meter to volts when you are finished with it. To test an unknown voltage start with the meter set to the highest voltage range. If you apply a high voltage to the meter set upon a low voltage range, you may damage the meter. For example connecting a meter set to 10 volts to a 110 volt wall outlet is a bad thing. Although quality meters (John Fluke) may survive this jolt, plenty of no name meters won't.
Measure the output voltage of your power pack with nothing but the meter connected to the power pack. If you get 0-12 VDC and 16 VAC that is a good sign. Hook the power pack to some track and run a locomotive. If the locomotive runs, all is well. If it doesn't, check for voltage right on the track with the locomotive on track. Various things can fail in power packs that cause them to fail to deliver power to a real load. And, most power packs have overcurrent protection, when they sense too much current going out (usually a short circuit) they shut down. If you have 12 volts on the rails, with the locomotive on the track, the power pack is doing it's job and the problem is with the locomotive.
Use the ohm meter ranges to check for short circuits in the track. With the power pack disconnected the track (no rolling stock) ought to read thousands of ohms. More is better. With a locomotive on the track the ohmeter ought to read a few ohms. This can be a little tricky. The electric motor, when not turning, is just a coil of wire across the rails, and looks pretty much like a short circuit to the meter.
David Starr www.newsnorthwoods.blogspot.com
rrebell Hey, you are making this way more complex than needed. All I wanted was set the meter to xxx for dc and yyy for ac. This is a transformer made for model railroading, just wanted to test it and know what settings to use instead of guessing as in the past. I know which output is which and what its output is soposed to be.
Go back and read your first post. You know your electrical and modeling background. We don't.