# Rheostat

Canonical URL: https://eloragrid.ai/protection-functions/70-rheostat
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: 70
Drawing use: SLD, Schematic
Reference families: IEEE / ANSI

Provides adjustable resistance in a control, excitation or machine circuit.

## What it represents

Provides adjustable resistance in a control, excitation or machine circuit.
In a drafting package, connect this reference to the resistance circuit, adjustment mechanism and operating range reference. The associated drawing should trace the rheostat terminals and drive/control interface; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings.
This designation is useful when reading machine and legacy control drawings. Retain the documented function on an existing drawing and consult the original equipment manual before assigning it to a new design.

## How to read it

- Identify the resistance circuit, adjustment mechanism and operating range reference.
- Trace the rheostat terminals and drive/control interface.

## Information to show or reference

- Label the resistance circuit, adjustment mechanism and operating range reference.
- Cross-reference the rheostat terminals and drive/control interface.
- Identify the device tag, manual revision and logic drawing that define this implementation.

## Important distinction

A rheostat is a variable resistor arrangement; it is not a complete voltage regulator.

## Facts

- ANSI / IEEE function number: 70
- Drawing context: The resistance circuit, adjustment mechanism and operating range reference
- Application scope: Specialist or legacy machine-control use; interpret with the equipment legend.

## Public references

- [ANSI device-number and suffix reference table](https://selinc.com/pt/products/tables/ansi/) — Schweitzer Engineering Laboratories. Public manufacturer number/name association. Drafting explanations are independently written.
- [IEEE C37.2-2022: power-system device function numbers](https://ieeexplore.ieee.org/document/9984140) — IEEE. Normative device-number publication; exact edition wording and compliance require the licensed standard.

## 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.