Hz Hz
Double frequency meter
Instrument with two frequency elements showing running and incoming frequency together on a synchronising panel.
SLD / Schematic
Symbols · V V
Double voltmeter
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.
- 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.
Read the source: IEC graphical symbols for diagrams · Generator switchgear and paralleling controls
SLD / Schematic · V V
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
A distinction that matters
A double voltmeter shows both voltages; a differential voltmeter shows only their difference.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
Generator switchgear and paralleling controls
Public context for generator paralleling controls where synchronising instruments are used.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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