Re: Dead track area dcc

Mark Gurries

On Jun 23, 2018, at 9:51 PM, vincent marino <vmarino2009@...> wrote:

How do you explain a dead track area when the voltmeter reads normal? 

You have a open connection.

Voltmeters can lie because they do not require any current to flow of any consequence to measure the voltage.  In other words you can have a very weak electrical connection that cannot support any current and the meter will say everything is OK.

The technical reason is the voltmeter has what is called a very high input impedance.   10 millions of Ohms AKA Megohms or input resistance so to speak.

You can see an example of this if you put the meter in AC mode on the lowest voltage setting and have each one of you hands hold one of the two test leads.  Watch…you have AC voltage!  Play around with this.

You body is acting like an antenna picking up electrical energy in the air.  The meter reads this very weak signal and display a value.

In electronics, one has to know the limitation of the test equipment they use.


Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics:

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