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Eye Tracking System Angle Meter

Overview Features Measuring Principle Concept Serial Interface
Coil Frame Search Coils More Information Specifications List of References

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Specifications
In General
Recording Channels Two channels in the Basic System, expandable by the use of up to two additional channel pairs to six channels 
AC Input Voltage AC input voltage: 230 VAC 10%, 50...60Hz
(115 VAC 10%, 50...60Hz on request)
Power Consumption 300 VA max.
LED-Display 7-Segment (Mode Indicator)
Control Elements Main switch,
multifunctional toggle-switch for the mode of each CPU Plug-In
Outline Dimensions 19" / 3 HU rack mountable or desktop case,
approx. 483 x 140 x 380 mm (w x h x d) 
Weight Basic system approx. 8 kg
Additional channel pair approx. 0.5 kg 
Performance (see also the diagrams below)
Output Data Rate 400 Hz
Recording Range 360 in the horizontal plane
70 in the horizontal plane
Resolution < 0.1
Noise < 0.3 peak-peak (search coil orientation: horizontal 180, vertical 0)
< 0.8 peak-peak (search coil orientation: horizontal 180, vertical 80)
Drift < 2 within 30 minutes after power-on (warm-up)
Linearity Horizontal < 0.7 deviation within 360
Vertical < 1 deviation between 70
Analog Outputs
Output Voltage Swing 9 V
Output Impedance 50 Ohm
Serial Interface
In General One serial interface (RS-232) transmits the data of 2 recording channels
Parameters 38'400 bps, no parity, 8 data bits, 1 stop bit
Preamplifier
In General Each preamplifier is located in a separate housing
Recording Channels 2 channels
Outline Dimensions 112 x 33 x 60 mm (w x h  x d) 
Weight 250 g
Coil Frame
In General Three coils with two turns each, arranged as a cube
Magnetic Flux Density 23 uT typical
Coil Material Anodized aluminium bars, cross section 8mm
Coil Color Various colors available, contact Primelec for further details
Dimension
Dimension L1 is freely definable within the range from 250 mm to 700 mm,
the other dimensions (L2 to L5) are resultant
L1: 250 ... 700 mm
L2: L1 - 16 mm
L3: L1 - 27 mm
L4: L1 + 36 mm
L5: L1 + 26 mm
Weight Depends on the coil dimensions, for example approx. 5 kg for L1 = 700 mm
Search Coils
Material Preferably double insulated copper wire, 20m
Weight Depends on material, dimensions and manufacturing process, 
for example approx. 2 mg for a double insulated copper coil with
D = 2mm and n = 80
DC-Resistance 75 Ohm max. (3 Ohm ... 40 Ohm typical)
Diameter 2 mm ... 40 mm typical (see also "Effective area")
Number of Turns 1... 630 typical (see also "Effective area")
Effective Area 2.5 cm2 ... 20 cm2 (Aeff = n D^2 pi / 4)
The range of the effective area specified above refers to the typical magnetic flux density. If the flux density is reduced by attenuating the field signals to 20 % of their nominal values, the allowed effective area may be up to approx. 150 cm2
Diagrams

Typical progression of the output voltage (horizontal plane)

Typical progression of the output voltage (vertical plane)

Warm-Up drift (Notes 2 to 4)

Horizontal linearity and crosstalk to vertical, Beta at 0 (Notes 1, 2, 4)

Vertical linearity and crosstalk to horizontal, Alpha at 180 (Notes 1, 2, 4)

Distribution of angular noise (Notes 1, 2, 5)

Note 1: Measured after 15 minutes warm-up delay with stepper-motor driven search coil under software control
Note 2: Used coil frame: formed as a cube, s = 70 cm
Used search coil: 15mm with 6 turns, placed in the 3D-center of the coil frame
The data was acquired over the serial interface 
Note 3: Measured with 6 channels working (i.e. max. internal power dissipation)
Note 4: Channel 1 and channel 2 in parallel at the same search coil (i.e. identical input signal)
Note 5: Each histogram is based on a recording with a total number of readings of 12000
(30 seconds at 400 readings / second) 

Copyright Primelec, D. Florin  ||  Ostring 36 8105 Regensdorf (Switzerland)