Track voltage measurement on DCS210+

[melmerby]

On 22/08/2021 at 08:42, SamThomas said:

To be honest, when proving the integrety of the wiring it really does not matter how accurate your meter is, as long as it is consistant.

 

Julian's original post was about measuring the accuracy of the voltage from the Digitrax unit.

[Nigelcliffe]

19 minutes ago, melmerby said:

Julian's original post was about measuring the accuracy of the voltage from the Digitrax unit.

 

It was,  and there's a measuring method described by Digitrax, for their systems, which works with a cheap DC voltmeter. 
 

(Before anyone says "AC, not DC" or "its not 50Hz, you need a Fluke" or "need a 'scope", please read Digitrax' documentation and explain where they've got the instructions for their systems wrong. )

 

- Nigel

[melmerby]

14 hours ago, Nigelcliffe said:

 

It was,  and there's a measuring method described by Digitrax, for their systems, which works with a cheap DC voltmeter. 
 

(Before anyone says "AC, not DC" or "its not 50Hz, you need a Fluke" or "need a 'scope", please read Digitrax' documentation and explain where they've got the instructions for their systems wrong. )

 

- Nigel

Yes I know.

As I understand it, they set it for a DC loco at address 0000, to produce a DC bias to the DCC signal.

Probably not supported by anyone else?

Edited August 25, 2021 by melmerby

[Nigelcliffe]

1 hour ago, melmerby said:

Yes I know.

As I understand it, they set it for a DC loco at address 0000, to produce a DC bias to the DCC signal.

Probably not supported by anyone else?

 

No.   But reading the manuals for those who own Digitrax gear will tell them what to do. 

 

- Nigel

 

 

[Grovenor]

Which the OP apparently did and was only querying the tolerances. 

[Crosland]

6 hours ago, melmerby said:

Yes I know.

As I understand it, they set it for a DC loco at address 0000, to produce a DC bias to the DCC signal.

 

Not quite. You set it for a DC loco with zero speed so there is NO DC bias. 

 

It then relies on the multimeter giving an average of the DCC voltage, which will be half of the track voltage.

 

I'm still not convinced every "cheap" multimeter will give useable data.

[Crosland]

After some more thought...

 

There's no need for selecting an unchipped loco on speed zero since any and every DCC bitstream has zero DC bias. That's why an unchipped loco will sit stationary (maybe humming and slowly cooking) if placed on a DCC layout.

 

The technique should work on any system. The trick seems to be taking the two measurements between the two rails and the 0V reference, rather than trying to measure the voltage directly across the rails.