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Eye Tracking System Angle Meter NT

Overview Features Measuring Principle Concept Included Software
Coil Frame Search Coils More Information Specifications List of References

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In General
Recording Channels 4 channels in the Basic System, expandable by the use of an Add-On Detector Module to 8 channels. Applications using more than eight measuring channels are also practicable, please contact us for details.
AC Input Voltage 230 VAC 10 %, 50 Hz (115 VAC 10%, 60 Hz on request)
Power Consumption 300 VA max. during normal operation, 5 VA max during Standby
LC-Display 2 x 16 characters, user selectable backlight intensity
Control Elements Main switch at the rear panel, Power On / Standby switch,
multifunctional rotary-/ push-button for the menu of each Detector Module (operation lockable by the user)
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. 10 kg,
Add-On Detector Module approx. 1 kg
Performance (see also the diagrams below)
In General User selectable output format of the readings:
- Linear angular data for the horizontal and the vertical plane
- Raw data for the X-, Y- and Z-signals
Output Data Rate Depending on the number of processed channels, user selectable:
- 4000 Hz (1 channel per Detector Module processed)
- 2000 Hz (2 channels per Detector Module processed)
- 1000 Hz (4 channels per Detector Module processed)
Recording Range 360 in the horizontal plane
80 in the vertical plane
Resolution < 0.05
Noise < 0.09 peak-peak (search coil orientation: horizontal 180, vertical 0)
< 0.36 peak-peak (search coil orientation: horizontal 180, vertical 80)
Drift < 0.1 within 30 minutes after power-on (warm-up), negligible after warm up
Linearity Error Horizontal Horizontal < 0.5 deviation within 360
Vertical < 0.3  deviation between 70
Channel Matching < 0.1 
Analog Outputs
Resolution 12 Bit
Output Voltage Swing User selectable:
2.5 V, 4.5 V, 5 V, 9 V, 10 V
Output Impedance 50 Ohm
Serial Interface
In General The bidirectional serial interface (RS-232) of each Detector Module transmits the measuring data and may be used to control the system
Parameters 115200 bps, 8 data bits, 1 stop bit, no parity
Handshake Mode Hardware (RTS / CTS)
Field Signals
In General Three sine wave field signals, (crystal-controlled digitally synthesized),
amplified by three physically separated power amplifiers with symmetrical outputs
Frequencies 80 kHz (X-axis)
96 kHz (Y-axis)
120 kHz (Z-axis)
Nominal Output Voltage Depend on the size of the field coils, where the nominal output voltages are tuned at the factory to achieve the specified flux density (see "Magnetic flux density") and an optimal field homogeneity at the 3D-centre of the field coils.
The factory-tuned nominal output voltages may be attenuated by the user in steps of 20 % down to zero
Maximum Output Voltage 26 Vpp referenced to system ground (52 Vpp differential measured)
Output Impedance 0.2 Ohm max.
In General Each preamplifier is loacted in a separate housing,
user selectable gain mode (AGC or user adjustable gain per channel)
Recording Channels 4 channels
Supply Voltage 5 V, 500 mA max. (power supply is provided by the Detector Module)
Outline Dimensions 100 x 40 x 200 mm (w x h x d)
Weight 330 g
Coil Frame
In General Three coils with two turns each, arranged as a cube
Optional version 'Removable Bars' available, which allows the straightforward opening of the coil frame, e.g. to insert a primate chair. 
Magnetic Flux Density 15 uT typical at the nominal output voltage of the field signals. The magnetic flux density may be attenuated by the user in steps of 20 % down to zero (see "Nominal output voltages")
Coil Material Anodized Aluminum bars, cross section 8 mm 
Coil Colors Various colors available, contact Primelec for further information
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 300 Ohm max. (3 Ohm ... 100 Ohm typical)
Diameter 2 mm ... 40 mm typical (see also "Effective area")
Number of Turns 1... 1000 typical (see also "Effective area")
Effective Area 1 cm2 ... 32 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

Typical progression of the output voltage (horizontal plane)

Typical progression of the output voltage (vertical plane)

Warm-Up drift (Notes 1 to 4)

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

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

Distribution of angular noise (Notes 1 to 5)

Note 1: Measurement executed with 8 channels working (i.e. max
internal power dissipation). The data was acquired over
the serial interface. Measuring channel 1 was used, where
the performance of all measuring channels is identical.
Used settings:
  • Field Signals: 100% of their nominal values
  • Gain Correction: Disabled
  • Gain Mode: AGC
  • Offset Correction: Disabled
  • Output Mode: Angular Data
  • Output Filter: Disabled
  • Output Swing: 9 V
  • Processing Mode: All four channels
Note 2: Measurement executed with a stepper-motor driven
search coil under software control
Note 3: Used coil frame formed as a monocoque cube, s = 70 cm
Note 4: Used search coil with an effective area = 10.8 cm2 ( 37 mm, 1 turn),
DC Resistance = 7 ohm, placed at the 3D-center of the coil frame 
Note 5: Distribution of angular noise is based on 5000 continuosly acquired samples

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