PR_1300395509_HH_Coil_Automation_Fixture_Requirements_revB.pdf

Helmholtz Coil Automation Fixture Requirements

Figure 1: Sensor Cylinder with motion and shock to be provided by automated fixture

General Requirements

• No ferrous metal can be used

• The fixture must be able to be installed and removed from the Helmholtz coil table by one technician

• The fixture must accept a cylinder with a 2” diameter and up to 8” long, as shown in Figure 1.

• Positioning within the Helmholtz coil

– Helmholtz Coil Sweet Spot: the point of greatest field uniformity in the Helmholtz coil after each coil alignment. It is currently maintained at the center of the Helmholtz coil table and 3.75” above the table surface. The table can be lowered 1” – 2” increasing that 3.75” distance if desired by the amount lowered.

– Compass Vertical: An infinitesimally small sensitive point on each compass, ideally centered on the sweet spot of the Helmholtz coil can move vertically less than or equal to 1" up or down from the sweet spot.

– Compass Horizontal: An infinitesimally small sensitive point on each compass, ideally centered on the sweet spot of the Helmholtz coil can move horizontally less than or equal to a 2” radial distance from the sweet spot.

Roll Requirements

• Initial position set: means to adjust and lock in the sensor cylinder at the initial 0° roll position

– Threshold for initial position: ± 0.05° accuracy

– Initial Position does not need to be automated – operator can set this position by hand, by manipulating the fixture manually or by sending step forward or back commands from our software. The operator would most likely use visual feedback from the compass under test during the initial position set – those readouts will be on display from our software at all times.

• Roll Motion from initial position set

– Bi-directional

– Range of 360° clockwise and counterclockwise, resolution: 10° increments or smaller, positioning accuracy ± 0.5° or better

– Must be fully automated – no operator input –commands from host computer (of type

TBD) will be sent from our software until our software determines the desired roll position has been reached, using output from the sensor under test and/or an encoder.

Pitch Requirements

• Initial position set: means to level the fixture so the initial sensor pitch is locked in at 0° pitch

– Initial Pitch threshold: ± 0.05° accuracy

– Initial Pitch Position does not need to be automated – operator can set this position by manual manipulation of the fixture or by sending commands (of type TBD) from our software. The operator would most likely use visual feedback from the compass under test during the initial position set – those readouts will be on display from our software at all times.

• Pitch Motion from initial position

– Bidirectional

– Range from -5° (+0°, -1°) to +5° (+1°, -0°), resolution of 5° increments

– Must be fully automated – no operator input

– Pitch position should remain constant through any roll position changes.

Shock Requirements

• Gentle shock for gimbaled sensor calibrations (automated equivalent of knocking on the current table set up as you would gently knock on someone’s door).

• Must be fully automated – no operator input

• Shock cannot be delivered through the pitch or roll motion controls or through pitch or rolling motions. Sensor roll and pitch position (and yaw of course) must remain constant before, during, and after shock.

Yaw Requirements

• Sensor yaw position should be locked in when the fixture is installed on the table

• Yaw position should not change during any of the roll and pitch motions described above or during the delivery of shock.

Helmholtz Coil Table

Figure 2 below gives rough dimensions of the Helmholtz coil table. Note that there is an identical table one foot to the right of the center table, but without the hole pattern.

Figure 2: Helmholtz Coil Table Dimensions (drawing not to scale)