DCC is very difficult to measure correctly. It is a 10khz square wave PWM network signal and not normal AC. Reading track voltage correctly on DCC can prove to be a challenge. The voltage available on the rails is a Digital PWM form of AC, not standard AC.
Test your meter first on a 120v AC wall outlet to verify you have the meter set correctly and it is functioning correctly. If you can read a wall outlet, you should be able to read a DCC track voltage.
A regular meter will not give 100% accurate readings on the rails or on the two-pin plug out on the back of the Power Cab Panel. But it can tell you if some sort of number to check for around your layout. regardless of what the number is, it should be consistent everywhere on your layout and track.
The Power Cab wall transformer Power Supply that plugs into the wall is a DC power supply with a DC output. The power supply that was included with your Power Cab may be one of several versions based on what was available to us at the time. The question is the voltage and current ratings of the actual power supply you have. Printed on the power supply you should see a voltage rating and a current rating. Something like: 12v dc or 13.8v dc. and 1.35A, 1.44A, or 1.8A current rating.
Makes sure your wiring is robust enough, so you have the full voltage and current capacity available of the Power Cab on your entire layout. also check out www.wiringfordcc.com For DCC wiring questions. Go here for more info: http://wiringfordcc.com/
If your Power Cab is older than 10 years, consider replacing the P114 Power Supply. 5240221
Otherwise, if you are truly having capacity issues, then get an SB5 booster- 5240027
Bear in mind that the DCC industry standard for HO scale is 14v. All NCE equipment designed for HO Scale is 13.8v. Again, reminding you that DCC is very difficult to measure correctly. It is a 10khz square wave network signal and not normal AC. The reading you see is pretty standard on a normal AC DVM.
If you do not own a multimeter here is a link to an inexpensive one from Home Depot - http://www.homedepot.com/p/Powerbuilt-Digital-Multi-Meter-648349/204505225
Lighted track bumpers should NOT be used with DCC. These will lower your track voltage AND lower your system capacity below 2amps.
The Power Cab has no voltage adjustment. The standard track voltage for HO scale is 14v. for N scale it is 12v. The incoming Power Supply for the Power Cab is 13.8 VDC. The track output as measured directly on the back of the Power Cab Panel (PCP) should read about 13.8v AC. DCC track voltage is difficult to read correctly with ANY type of meter. It is a Digital PWM square wave and is closer to a computer signal than anything else.
Getting correct voltage readings on the track relies heavily on using the proper gauge wiring for your DCC track bus and track feeders. Your DCC track bus wire should be either 14 or 12ga. wire with track feeders every three feet. Track feeders should be either 20 or 18. ga if you are in HO scale. The wire supplied by Kato is not sufficient for reliable long term operation. Also you need to take into account that the rail joiners are only good for a PHYSICAL connection and rail alignment. They are horrible for track power and should not be relied upon for electrical connections. You can also solder some of the pieces together, that will help.