# Double voltmeter

Canonical URL: https://eloragrid.ai/symbols/double-voltmeter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: V V
Drawing use: SLD, Schematic
Reference families: IEC, Manufacturer

Instrument with two voltage movements in one case, showing running and incoming voltage side by side for synchronising.

## In plain English

### What does Double voltmeter mean?

A double voltmeter contains two voltage measuring elements, usually reading the running busbar and the incoming generator or feeder. Mounted on a synchronising panel next to the double frequency meter and synchroscope, it lets the operator match voltages before closing.

### A simple example

The two inputs must come from VTs with equivalent ratios and the same phase pair, otherwise the comparison is misleading. The symbol does not show the switching that selects which incoming source is connected to the instrument.

### What the drawings help you do

Identify which input is running and which is incoming. Check the synchronising selector that switches the inputs. A double voltmeter shows both voltages; a differential voltmeter shows only their difference.

### This particular reference

Instrument with two voltage movements in one case, showing running and incoming voltage side by side for synchronising. A double voltmeter shows both voltages; a differential voltmeter shows only their difference.

### Terms

- Phase: One of the related AC waveforms in a power system.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)
- [Generator switchgear and paralleling controls](https://www.cummins.com/en-na/generators/products/switchgear)


## What it represents

A double voltmeter contains two voltage measuring elements, usually reading the running busbar and the incoming generator or feeder. Mounted on a synchronising panel next to the double frequency meter and synchroscope, it lets the operator match voltages before closing.
The two inputs must come from VTs with equivalent ratios and the same phase pair, otherwise the comparison is misleading. The symbol does not show the switching that selects which incoming source is connected to the instrument.

## How to read it

- Identify which input is running and which is incoming.
- Check the synchronising selector that switches the inputs.

## Information to show or reference

- Label both inputs
- Show VT ratios
- Reference sync selector switch

## Important distinction

A double voltmeter shows both voltages; a differential voltmeter shows only their difference.

## Facts

- Inputs: Running and incoming voltage
- Location: Synchronising panel
- Preview: Independent educational concept; consult the applicable standard and project legend for the exact graphic

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
- [Generator switchgear and paralleling controls](https://www.cummins.com/en-na/generators/products/switchgear) — Cummins. Public context for generator paralleling controls where synchronising instruments are used.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.