Published 24 August 2026 at 13:09
Most people reading a dial test indicator’s datasheet look at two figures: the graduation and the accuracy. The third figure — hysteresis — is almost always skipped, even though it’s the one that determines how the instrument can actually be used in practice.
Hysteresis is the difference in reading depending on which direction the stylus approached the same point from. On this indicator it’s at most 0.004 mm, while the graduation is 0.002 mm. In other words: reverse the direction of travel and the needle can end up up to two graduation marks off, without anything at all having happened to the workpiece.
What it is
A horizontal dial test indicator from Peacock, lever type.
- Measuring range 0.28 mm, graduation 0.002 mm, dial numbering 0-140-0
- Accuracy ±0.005 mm, max hysteresis 0.004 mm
- Measuring force under 0.3 N
- Dial Ø35 mm, lug back mount Ø6 mm
- Tungsten carbide measuring tip Ø2 mm, M1.7 thread, contact point length 17.94/14.33 mm
- Plastic case including the manufacturer’s inspection certificate
The problem it solves
The consequence of hysteresis is a rule of practice, not a problem: always approach the measuring point from the same direction. If you zero it by moving the tip inward, every subsequent reading should also be taken with the tip moving inward. It’s the same discipline as backlash in a machine screw, and it costs nothing to follow — but anyone who doesn’t know the figure also doesn’t know it’s needed, and instead wonders why two measurements of the same surface differ by a couple of thousandths.
It matters even more when scanning a surface. If you sweep back and forth across a part to find the highest point, the tip changes direction on every turn, and some of the spread you see then comes from the instrument rather than the workpiece. If you instead sweep consistently in one direction and lift back, that part disappears.
The measuring force under 0.3 N is the dial test indicator’s real distinguishing feature. An ordinary dial indicator pushes with several newtons — enough to bend a thin part, shift a loosely clamped workpiece, or compress a rubber surface. A lever-type indicator touches the part so lightly that it can be used on thin sheet metal, on springy parts, and in setups that would otherwise give way under the measurement itself.
Tungsten carbide on the tip is not a luxury but a necessity. Unlike a dial indicator, whose tip is pressed straight down, the dial test indicator’s tip drags across the surface as the measured object is moved past it. It therefore wears continuously, and a worn tip changes both the contact geometry and the zero point. Carbide lets it keep its shape through years of use.
Three typical use cases
- Alignment in a machine: centering and runout checks, where the instrument needs to reach into tight positions with little force.
- Checking flatness and parallelism: scanning surfaces against a fixed reference.
- Fixture work: setting stops and position sensors, where 0.002 mm graduation is needed and the part must not be moved by the measuring force.
Why it pays off
An instrument with 0.002 mm graduation is in practice only worth its graduation if the user knows how to move it. The difference between measuring with and against the direction of travel is not a theoretical nicety — it’s on the order of two graduation marks, which is exactly the resolution you bought the instrument for.
Having the manufacturer’s inspection certificate included is what completes the picture: the figures on the datasheet then apply not just to the model, but to the exact unit in the case. That’s the difference that lets a reading be entered into a report instead of merely serving as the basis for a decision.
Read more about the Peacock horizontal dial test indicator →
