Hardware Support: Digitrax "Meters"

Introduction to JMRI Volt and Current Meters with Digitrax Hardware
Hardware which supports Digitrax "Meters"
Limitations

Introduction to JMRI Volt and Current Meters with Digitrax Hardware

Under certain configurations, JMRI provides a "Voltage/Current Meter" tool under the "Tools" menu item. This tool may be used to display information reported by certain Digitrax hardware.

The Voltage/Current Meter tool can report voltage or current data from any LocoNet device which reports voltage and current information using special Loconet messages. In order to help differentiate the possible sources, each source's data is identified by a name which includes the device type and the device serial number. Each is individually selectable in the Voltage/Current Meter tool.

It is helpful to re-configure the Voltage/Current Meter tool's "Settings" for displaying "2 integer digits" and "1 decimal digit". This matches the tool's display to the precision of the data reported on LocoNet.

Note that the current reported by modern Digitrax boosters and command stations tends to be the "power input" current, not the "DCC Track Current". See Limitations, below.

Hardware which supports Digitrax "Meters"

The JMRI's LocoNet functionality supports the voltage and current reporting from the following Digitrax devices:

Device		Typical "name" of voltage meter	Typical "name" of current meter
DCS210	TVDCS210(s/n130)Voltage	TVDCS210(s/n130)InputCurrent
DCS240	TVDCS240(s/n4567)Voltage	TVDCS240(s/n4567)InputCurrent
DCS52	TVDCS52(s/n100)Voltage	TVDCS52(s/n100)InputCurrent
DCS210+ *	TVDCS210+(s/n93)Voltage	TVDCS210+(s/n93)InputCurrent
DB210 **	TVDB210(s/n435)Voltage	TVDB210(s/n435)InputCurrent
DB220 **	TVDB220(s/n2117)Voltage	TVDB220(s/n2117)InputCurrent
DB210Opto **	TVDB210Opto(s/n435)Voltage	TVDB210Opto(s/n435)InputCurrent
* At least some DCS210+ devices report inconsistent data.
** It is suspected that these devices report voltage and current data that is compatible with this tool, but this has not yet been confirmed.

Other Digitrax devices which include the appropriate capabilities are automatically supported. However, where a specific device type is not understood by JMRI, the associated voltage meter and current meter data will be available, via names which include a device number instead of a device name.

Limitations

The LocoNet implementation which supports reporting of voltage and current has the following limitations:

The JMRI implementation of voltage and current measurement capabilities applies to those devices which support "Query Mode" reporting of voltage and current mesurements.
At least some versions of DCS210+ command stations seem to have problems in reporting reliable data.
Proper reporting of voltage and current measurements may only be available with certain firmware versions. Be sure to update your LocoNet device firmware to help ensure proper measurement reporting.
When displaying LocoNet-reported Voltage and/or Current values, the tools will generally receive new data about every 30 seconds.
While the tool linked in the "Tools" menu calls one tool "Track Current", the LocoNet implementation does not report DCC track current exactly. Instead, the LocoNet implementation reports the "input power's current consumption". This will generally be the DCC track current plus some "overhead" current which is consumed by the command station circuitry.
The LocoNet implementation relies upon the information reported by the "Query Mode" reporting of "Vtrk" (for the data used by the "Track Voltage" tool) and "Query Mode" reporting of "Iin" (for the data used by the "Track Current" tool).

LocoNet® is a registered trademark of Digitrax, Inc.

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