# ANSI/IEEE differential voltmeter symbol

Canonical URL: https://eloragrid.ai/symbols/ansi-differential-voltmeter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: ΔV
Drawing use: Schematic
Reference families: IEEE / ANSI, Manufacturer

## Symbol convention

Convention: IEEE / ANSI
Form: Autodesk IEEE-oriented Instrumentation and Sensors form: Differential Voltmeter
Autodesk publishes this block under its IEEE Symbol Preview. The counterpart is the matching functional concept in the library; no equivalence of every detailed standard graphic is asserted.
Related representation: [Differential voltmeter](https://eloragrid.ai/symbols/differential-voltmeter)

IEEE-library differential voltmeter form reading the difference between two voltages, for example across a synchronising point.

## In plain English

### What does ANSI/IEEE differential voltmeter mean?

A differential voltmeter reads the difference between two applied voltages rather than either voltage alone. In synchronising panels it is wired between the incoming and running VT secondaries so the operator can see when the voltage difference is small enough to close the breaker.

### A simple example

The symbol does not show whether both inputs come from the same phase, or whether VT ratios are matched. If the two VTs have different ratios or phase shifts through a transformer, the reading is meaningless unless interposing correction is drawn.

### What the drawings help you do

Confirm both inputs are taken from the same phase pair. Check the VT ratios on both sides of the closing point. A differential voltmeter shows the difference between two voltages; a double voltmeter shows both voltages on separate scales.

### This particular reference

IEEE-library differential voltmeter form reading the difference between two voltages, for example across a synchronising point. A differential voltmeter shows the difference between two voltages; a double voltmeter shows both voltages on separate scales.

### Terms

- Winding: A coil of conductor inside an electrical machine or transformer.
- Phase: One of the related AC waveforms in a power system.
- Terminal: An identified point where a conductor connects.

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.

- [Autodesk IEEE Symbol Preview — Instrumentation and Sensors](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-F44D5059-4728-40BD-B9BA-0DE7CFDFAACF.htm)
- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/)


## What it represents

A differential voltmeter reads the difference between two applied voltages rather than either voltage alone. In synchronising panels it is wired between the incoming and running VT secondaries so the operator can see when the voltage difference is small enough to close the breaker.
The symbol does not show whether both inputs come from the same phase, or whether VT ratios are matched. If the two VTs have different ratios or phase shifts through a transformer, the reading is meaningless unless interposing correction is drawn.

## How to read it

- Confirm both inputs are taken from the same phase pair.
- Check the VT ratios on both sides of the closing point.

## Information to show or reference

- Identify both voltage sources
- Show phase reference
- Note any ratio or angle correction

## Important distinction

A differential voltmeter shows the difference between two voltages; a double voltmeter shows both voltages on separate scales.

## Facts

- Convention evidence: Autodesk IEEE Symbol Preview, Instrumentation and Sensors
- Public vendor block name: HVM1P7 / VVM1P7 (Autodesk identifier; not an IEEE symbol number)
- Typical location: Synchronising panel across a closing point
- Artwork scope: Original functional illustration; exact standard glyph and compliance are not certified

## Public references

- [Autodesk IEEE Symbol Preview — Instrumentation and Sensors](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-F44D5059-4728-40BD-B9BA-0DE7CFDFAACF.htm) — Autodesk. Public IEEE-oriented Instrumentation and Sensors preview listing the Differential Voltmeter block and its vendor identifier.
- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/) — IEEE Standards Association. Graphic-symbol standards context and official status; not a source of reproduced artwork.

## 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.