Analog or Digital Dial Indicator - Which One?
A dial indicator converts the smallest travel of a spring-loaded plunger into a readable display. This guide shows how to choose between analog and digital while weighing measuring range, graduation value and the accuracy classes of DIN 878.
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How does a dial indicator work and what does it measure?
A dial indicator turns the linear motion of a spring-loaded plunger into a rotation of the pointer through a rack-and-gear train. It does not read absolute size but differences from a set zero point, for example deviation from a reference surface.
That makes it the standard tool for comparative inspection: runout of a shaft, flatness of a plate or parallelism of two faces. The plunger is set against the workpiece, zeroed, and the display shows the deflection directly.
- Plunger: spring-loaded, transmits travel to the gear train.
- Dial face: main pointer shows tenths, small counter counts revolutions.
- Tolerance markers: adjustable pointers flag go/no-go limits.
- Mounting: plunger stem or 8 mm back lug for holder fixing.
Analog or digital - which type suits your inspection?
Analog indicators show motion and trend instantly and suit fast runout checks where the pointer movement itself is the information. Digital indicators offer unambiguous reading, switchable units (mm/inch) and a data output for documentation.
- Choose analog for dynamic runout and axial checks and battery-free continuous use.
- Choose digital for single-dimension checks, series inspection with data capture and mixed mm/inch work.
- Digital fine indicators reach graduation values down to 0.001 mm for highest resolution.
Choosing measuring range and graduation correctly
Two figures drive the choice: the measuring range (the full usable travel of the plunger) and the graduation value (the smallest readable step). The range must cover the expected deviation with reserve; the graduation sets how fine you can read.
A useful rule of thumb: the graduation should be about one tenth of the tolerance under inspection. A 0.1 mm tolerance is fine with 0.01 mm; for tight tolerances below 0.02 mm a fine indicator with 0.001 mm belongs on the bench.
What does DIN 878 require for accuracy?
DIN 878 defines the permissible error limits for dial indicators with 0.01 mm graduation: for total range, partial range, hysteresis and repeatability. This makes indicators from different makers comparable and lets you prove suitability for a given tolerance check.
- Total error span f_ges: maximum error over the whole travel.
- Hysteresis f_u: difference between rising and falling measurement.
- Repeatability f_w: scatter when probing the same point several times.
- Local error f_e: error over a partial section, e.g. 1/10 of a revolution.
Frequently asked questions
What does graduation value mean on a dial indicator?
The graduation value is the smallest readable step, usually 0.01 mm on standard indicators and 0.001 mm on fine indicators. It sets how finely you can read deviations.
Analog or digital for runout inspection?
For dynamic runout the analog indicator often wins because the pointer movement shows the deviation directly. Digital pays off when single values must be documented or captured via data output.
What accuracy does DIN 878 require?
DIN 878 defines error limits for indicators with 0.01 mm graduation covering total range, hysteresis and repeatability. This lets you prove suitability for a specific tolerance.
How large must the measuring range be?
The range should cover the expected deviation with reserve but not be larger than needed. Common ranges are 3 to 30 mm; for finest measurements 1 to 5 mm is often enough.
Looking for the right dial indicator?
We supply analog and digital dial indicators plus fine and lever-type test indicators - tested to DIN 878 with calibration certificate available.
Standard-tested
Indicators to DIN 878 with documented error limits.
Calibratable
Factory calibration certificate for traceability on request.
0.01 to 0.001 mm
Matching graduation for every tolerance.
Expert advice
Metrology specialists help you choose.