Lafayette Data Acquisition Sub Sensor (DAS) Specifications

Published parameters used to acquire the Lafayette polygraph system's EDA signal.

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Lafayette Data Acquisition Sub Sensor (DAS) Specifications

Published parameters used to acquire the Lafayette polygraph system's EDA signal.

The American Polygraph Association (APA) executive leadership invited all the North American polygraph instrument manufacturers to participate in the creation of a standard for EDA signal processing. In an effort towards transparency and scientific responsibility, one of the standards states:

Instrument manufacturers shall publish all parameters used to acquire the EDA signal. This shall include but is not limited to: type of circuit used (constant current or constant voltage), measurement units, excitation current or voltage level, recommended electrode type, type of electrodes used, electrode location or placement, number and types of filters used along with corner frequencies and other necessary parameters.

 

LX6

  • Type of circuit used:
    • GSR mode: Constant Current
    • GSC mode: Constant Voltage
  • Measurement Units: Ohms
  • Excitation:
    • GSR: 4uA
    • GSC: Auto-ranging- Current limited to 10uA, Voltage limited to 5 volts (mutually exclusive).
  • Recommended Electrode type: Solid Gel or Stainless Steel
  • Electrode type used: Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system.
  • Recommended Electrode Placement: the volar surface of distal or medial phalanges, thenar and hypothenar surfaces of the palm, and two sites at the inner aspect of the foot, over the abductor hallucis muscle adjacent to the sole of the foot and midway between the proximal phalanx of the big toe and a point directly beneath the ankle.
  • Filtering:
    • Hardware
      • 1.59 Hz Low Pass
    • Software Manual Mode:
      • 12 Hz Low Pass
      • 0.44 Hz Low Pass
    • Software Automatic Mode:
      • 0.0159 Hz High Pass, 10 Second time constant

LX5000

  • Type of circuit used:
    • GSR mode: Constant Current
    • GSC mode: Constant Voltage
  • Measurement Units: Ohms
  • Excitation:
    • GSR: 4uA
    • GSC: Auto-ranging- Current limited to 10uA, Voltage limited to 5 volts (mutually exclusive).
  • Recommended Electrode type: Solid Gel or Stainless Steel
  • Electrode type used: Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system.
  • Recommended Electrode Placement: the volar surface of distal or medial phalanges, thenar and hypothenar surfaces of the palm, and two sites at the inner aspect of the foot, over the abductor hallucis muscle adjacent to the sole of the foot and midway between the proximal phalanx of the big toe and a point directly beneath the ankle.
  • Filtering:
    • Hardware
      • 1.59 Hz Low Pass
    • Software Manual Mode:
      • 12 Hz Low Pass
      • 0.44 Hz Low Pass
    • Software Automatic Mode:
      • 0.0159 Hz High Pass, 10 Second time constant

LX4000B

  • Type of circuit used:
    • GSR: Constant Current
  • Measurement Units: Ohms
  • Excitation:
    • GSR: 6.7 uA
  • Recommended Electrode type: Solid Gel or Stainless Steel
  • Electrode type used: Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system.
  • Recommended Electrode Placement: the volar surface of distal or medial phalanges, thenar and hypothenar surfaces of the palm, and two sites at the inner aspect of the foot, over the abductor hallucis muscle adjacent to the sole of the foot and midway between the proximal phalanx of the big toe and a point directly beneath the ankle.
  • Filtering:
    • Hardware
      • 1.59 Hz Low Pass
    • Software Manual Mode:
      • 12 Hz Low Pass
      • 0.44 Hz Low Pass
    • Software Automatic Mode:
      • 0.0159 Hz High Pass, 10 Second time constant
 

LX6

LX5000

LX4000B
Type of circuit used: GSR mode: Constant Current
GSC mode: Constant Voltage		 GSR mode: Constant Current
GSC mode: Constant Voltage		 GSR mode: Constant Current
Measurement Units: Ohms Ohms Ohms
Excitation: GSR: 4uA
GSC: Auto-ranging- Current limited to 10uA, Voltage limited to 5 volts (mutually exclusive)		 GSR: 4uA
GSC: Auto-ranging- Current limited to 10uA, Voltage limited to 5 volts (mutually exclusive).		 GSR: 6.7 uA
Recommended Electrode type:* Solid Gel or Stainless Steel Solid Gel or Stainless Steel Solid Gel or Stainless Steel
Electrode type used: Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system. Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system. Solid Gel or Stainless Steel Plate electrodes are standard supplied with the system.
Filtering (Hardware): 1.59 Hz Low Pass 1.59 Hz Low Pass 1.59 Hz Low Pass
Filtering (Software Manual Mode): 12 Hz Low Pass
0.44 Hz Low Pass		 12 Hz Low Pass
0.44 Hz Low Pass		 12 Hz Low Pass
0.44 Hz Low Pass
Filtering (Software Automatic Mode): 0.0159 Hz High Pass, 10 Second time constant 0.0159 Hz High Pass, 10 Second time constant 0.0159 Hz High Pass, 10 Second time constant

* Recommended Electrode Placement:

  • Volar surface of distal or medial phalanges
  • Thenar and hypothenar surfaces of the palm
  • Two sites at the inner aspect of the foot
  • Over the abductor hallucis muscle adjacent to the sole of the foot
  • Midway between the proximal phalanx of the big toe
  • A point directly beneath the ankle

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