---
title: Dial indicator
lang: en
type: notion
tags:
  - mme
  - notion
prerequis: []
aa: []
draft: false
source_fr: meca/comparateur.md
source_sha256: ddfb8be9f0d1ca28b42e1adfb60dd22b8787ca190afde895a087fa2f8ad676dc
---

A **dial indicator**, whether it reads on a dial or digitally, is a measuring instrument that shows **how far a position has moved** relative to a reference, to a hundredth of a millimetre. It does not measure an absolute dimension, it measures a variation.

![Diagram of a dial indicator mounted on a rigid stand and base: the plunger touches a rotating shaft, and any movement of the plunger deflects the pointer on the dial. The instrument shows a variation, not an absolute dimension.](/ressources/img/comparateur/battement.svg)

## In the project

The dial indicator serves to quantify whatever *moves*: play in a joint, runout on a rotating shaft, flatness of a seat, drift of a part under load. On the running example, it measures the **play** in one of the arm's joints, its runout and its travel, while characterising a test bench during the [[preuve-de-concept-en|proof of concept]]. Like any instrument, it has to be **characterised before use** and mounted on a rigid support. A badly zeroed indicator reports a drift that is not there, which is a [[precision-de-mesure-en|systematic error]].

*Zeroing, metrological calibration and uncertainty analysis belong to the metrology lab sessions and to the **mechanical engineering course**. The wiki places the instrument within the project.*

## See also

- [[pied-a-coulisse-en|Vernier caliper]] — for absolute dimensions
- [[preuve-de-concept-en|Proof of concept]] — characterising a test bench
- [[integration-et-tests-en|Integration and testing]] — dimensional inspection of the parts
- [[precision-de-mesure-en|Accuracy, trueness, precision]] — resolution is not accuracy, systematic error is not random error (cross-cutting to any measurement)
- **Mechanical engineering and metrology course** (colleagues) — calibration, uncertainties