The Nikon AE-7/AE-7C Automatic Levels are precision instruments designed for surveying in civil engineering and architectural constructions. These levels are engineered to provide accurate horizontal lines with minimal adjustment, ensuring uniform surveying accuracy and eliminating sighting errors. A key feature is their waterproofed telescopes, allowing them to be used reliably in moist conditions, including rain or tunnel constructions. The AE-7C model is identical to the AE-7 but includes a horizontal circle for additional functionality.

Function Description:

The primary function of the Nikon AE-7/AE-7C automatic levels is to establish and measure horizontal lines for various surveying tasks. The instruments achieve this through an internal automatic compensation mechanism that adjusts for slight inclinations of the instrument body, ensuring the line of sight remains truly horizontal. This automatic compensation range is ±16 arc minutes.

The AE-7C model extends this capability by incorporating a horizontal circle, which allows for angular measurements in the horizontal plane. The horizontal circle can be set to a desired position using its revolver, with each division representing 1 degree or 1 gon.

Distance measurement is also possible using the stadia lines etched within the viewfield. By reading the length 'l' on a rod imaged between the two stadia lines, and multiplying it by the stadia multiplying constant (100), the distance 'L' from the instrument center to the target can be determined. The stadia additive constant for these models is 0.

Important Technical Specifications:

Telescope: Internal focusing, anallactic optical system.
Image: Erect.
Magnification: 30X.
Effective Aperture of Objective: 40mm (1.57in).
Angle of Viewfield (at 100m / 100ft): 1°30' (2.6m / 2.6ft).
Shortest Focusing Distance: 0.3m (0.98ft).
Stadia Multiplying Constant: 100.
Stadia Additive Constant: 0.
Automatic Level Compensation Range: ±16'.
Sensitivity of Circular Level: 10'/2mm.
Horizontal Circle (AE-7C only): Minimum increment 1° (1gon).
Weight and Dimensions:
- AE-7 Instrument: 220 x 136 x 142mm, 1.70kg (8.7 x 5.4 x 5.6 in, 3.7lb).
- AE-7C Instrument: 220 x 136 x 142mm, 1.70kg (8.7 x 5.4 x 5.6 in, 3.7lb).
- AE-7 Plastic case: 379 x 195 x 197mm, 1.80kg (14.9 x 7.7 x 7.8in, 4.0lb).
- AE-7C Plastic case: 379 x 195 x 197mm, 1.90kg (14.9 x 7.7 x 7.8in, 4.2lb).

Complete Equipment:

Main body (1)
Objective cap (1)
Plastic case (1)
Hexagonal wrench (2)
Plumb bob (AE-7C only) (1)

Usage Features:

Tripod Setup: The instrument should be mounted on a tripod, ensuring the tripod head is approximately level.
Mounting the Instrument: The instrument is gently removed from its plastic case and secured to the tripod using the lock screw from underneath.
Leveling the Instrument: The circular level indicates the instrument's inclination. The air bubble must be placed inside the brown circle, which signifies the instrument is within its automatic compensation range (±16'). For higher accuracy, the air bubble should be centered precisely within the brown circle. When using a spherical head tripod, the lock screw can be slightly loosened to slide the instrument along the spherical head until the air bubble is centered, then tightened.
Diopter Adjustment: After removing the objective cap, the eyesight adjusting ring on the eyepiece is turned to focus on the crosshairs within the viewfield, eliminating parallax.
Focusing on the Target: The optical sight is used to aim at the target. The horizontal fine-motion knob brings the target to the center of the viewfield, and the focusing knob is used to achieve a sharp focus. It is crucial to ensure no parallax exists.
Checking Horizontality: The circular level is checked from the eyepiece side using the mirror. If the air bubble is within the brown circle, the line of sight is horizontal. If not, the leveling screws are adjusted to bring the bubble back into the circle.
Surveying (Measuring Height Difference): To measure height differences between two points (A and B), the instrument is set up halfway between them. Readings are taken from rods placed at points A and B. The difference between these readings gives the height difference.
Focusing Knob: The focusing knob features a coaxial coarse/fine focusing mechanism. The rotation torque changes during operation; a heavy feel indicates coarse focusing, while a light feel indicates fine focusing. The coarse/fine switching is automatic, starting with fine motion and switching to coarse after approximately 120° of rotation. Turning in the opposite direction returns to fine motion. The speed ratio between coarse and fine focusing is approximately 5:1.
Parallax Elimination: Parallax, a focusing difference between crosshairs and the target, causes eye fatigue and inaccurate measurements. To check for parallax, the eye is moved vertically and horizontally while looking through the eyepiece. If the relative position of the target and crosshairs changes, parallax exists. Refocusing on both the crosshairs and the target eliminates it.
Automatic Compensation: The internal adjusting mirror automatically compensates for instrument body inclination within a ±16' range. Tapping the tripod lightly should cause the target image to move inside the viewfield if the compensation function is working correctly.
Horizontal Circle (AE-7C only): The horizontal circle can be set to any desired position using its revolver.

Optional Accessories:

Plane Parallel Micrometer-3: This accessory enables parallel vertical translation of the optical axis. The amount of translation is indicated on a micrometer drum, allowing for precise rod readings down to 0.1mm.
- Attachable type.
- Measuring range: ±5mm/100 divisions.
- Minimum reading: 0.1mm/1 division.
- Measuring accuracy: within 0.05mm.
- Clockwise rotation raises the optical axis, counterclockwise rotation lowers it.
Illuminator-3: Used to light up the crosshairs in the viewfield, particularly useful in dark conditions like night or tunnels.
- Power source: External power source or two AA-type batteries (1.5V) connected in series.
- Lamp bulb: Specified miniature lamp bulb (3V).
- Usage: For battery use, remove the upper cover and insert batteries. For external power, connect the specified cord. Attach the illuminator to the object hood, then turn the light volume to adjust brightness. When changing the lamp, turn off power, remove the upper cover, and wait for the bulb to cool.
Diagonal Eyepiece Prism: To install, unscrew the existing eyepiece, replace it with the diagonal eyepiece prism, and then mount the eyepiece onto the open end of the diagonal eyepiece prism.
Zenith Prism: Attaches directly to the eyepiece.

Maintenance Features:

Carrying: The instrument should always be carried in its case. If carried attached to a tripod, keep it vertical and never support it on the shoulder.
Rain: While the instrument is waterproof and can be used in rain, it is essential to wipe off all moisture after use.
Storage: Store the instrument in a shady, dry place.
Cleaning Lenses: Smudges and finger marks on lenses should be removed using soft tissue or a soft, washed-out cotton cloth free from lint and grease.
Cleaning Plastic Case: Use neutral detergent. Avoid organic solvents like thinner, ethyl alcohol, or xylene.
Attaching Screws: Do not overtighten or loosen the attaching screws, as their firmness is precisely set to maintain optimal instrument performance.
Periodic Checking and Adjustment: The instrument should be checked periodically to ensure its best performance.
- Circular Level Adjustment: If the air bubble moves away from the center when the telescope is turned 180°, adjustment is needed. Use leveling screws to move the bubble halfway back, then use the supplied hexagonal wrench to turn the circular level adjusting screws to center the bubble. The mirror can be flipped up and turned 90° for easier adjustment.
- Horizontality of the Line of Sight Adjustment: This involves a two-rod test. Set two rods (F and R) 70-100m apart, with the instrument halfway between them. Take readings (F1, R1). Then, reset the instrument 2m from rod R and take new readings (F2, R2). If F1-R1 ≠ F2-R2, adjustment is required. Calculate F3 = R2 + (F1-R1). Unscrew the reticle adjusting screw cover near the eyepiece. Sight the distant rod (F) and adjust the reticle adjusting screw with the hexagonal wrench until the line of sight points to F3. Re-check to confirm F1-R1 = F2-R2.

Nikon AE-7 - Diagonal Eyepiece Prism; Zenith Prism Attachment

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