Product Description
Q: What does erect image in a telescope means?
In an auto level, circular level sensitivity means how much tilt it takes to move the bubble by a defined amount(usually one graduation or to the edge of the circle).
What it tells you in practice
- More sensitive vial = bubble moves a lot with a tiny tilt → harder to center, but indicates small tilt changes.
- Less sensitive vial = bubble barely moves with small tilt → easier to center, but less “fine” indication.
How it’s specified
Manufacturers usually state it as an angular value per bubble division, commonly in:
- minutes of arc per division (e.g., 8′ / 2 mm), or
- mm per meter (less common for circular vials), or
- sometimes just “8′” or “10′” as a shorthand sensitivity.
A typical circular bubble on an auto level might be around 8′ to 10′ per 2 mm (varies by model).
Why it matters on an auto level
The circular level is mainly for rough leveling so the compensator is within its working range. If you’re too far out of level, the compensator can’t correct and you’ll get:
- unstable crosshair/line of sight,
- limited or incorrect compensation,
- out-of-spec readings.
So the sensitivity is basically: “How picky is the bubble about tilt?”—and it relates to how precisely you can (and need to) level the instrument before measuring.
If you tell me the make/model of your auto level, I can interpret the exact spec from its manual (e.g., what “8′/2 mm” means in terms of how far the instrument can be off-level).
Q: What is the Multiplication factor in the Auto Level?
In an auto level, the multiplication factor almost always means the stadia multiplication constant (also called the stadia factor, usually written k).
It’s the number you multiply the stadia intercept by to get the horizontal distance from the instrument to the leveling staff.
What you measure
If your reticle has three horizontal hairs (upper stadia, center crosshair, lower stadia):
- Read the staff at the upper hair = RuRu
- Read the staff at the lower hair = RlRl
- Stadia intercept = s=Ru−Rls=Ru−Rl
Distance formula
D=k⋅s+CD=k⋅s+C
- DD = horizontal distance (meters if the staff is metric)
- kk = multiplication factor (stadia factor)
- ss = stadia intercept (meters)
- CC = additive constant (often ~0, sometimes ~0.3 m depending on optics)
Typical value
For most auto levels:
- k≈100k≈100
- C≈0C≈0 (or very small)
So in many cases you can use the quick field rule:
D≈100⋅(Ru−Rl)D≈100⋅(Ru−Rl)
Example
If Ru=1.865Ru=1.865 m and Rl=1.645Rl=1.645 m, then:
- s=0.220s=0.220 m
- D≈100×0.220=22.0D≈100×0.220=22.0 m (plus CC if your instrument specifies one)
If you share your auto level brand/model (Topcon, Sokkia, Leica, GeoMax, etc.), I can tell you the exact kk and CC that the manufacturer lists for it.