The fingertip skin conductance sensor has two snap leads for easy connection to disposable snap sensors or reusable snap sensors with finger bands.
Procomp+ SCR assembly is made up of two pieces. The SA9309P cable is approximately 48 in (122.5 cm) in length and is terminated with two snap receptacles. Two SE35 hook and loop fastener (AgAgCL button) style finger sensors simply snap into the cable. The button sensor, approximately 8mm in diameter, is embedded into the hook and loop fastener band and secured around the finger by connecting the hook and loop fastener.
The standard measurement unit for conductance is Siemens. Skin Conductance is measured in micro-Siemens. Some biofeedback systems display skin conductance in micro-mhos (um) - a mho is the inverse of an ohm, which is the measure of resistance. These two measures, uS and um, are equivalent. Normal reading, for skin conductance, in a relaxed state are around 2 uS, but reading can vary greatly with environmental factors and skin type.
How it Works
Skin conductance is a measure of the skin's ability to conduct electricity. A tiny electrical voltage is applied through two sensors, usually strapped to two fingers of one hand, in order to establish an electric circuit where the body becomes a variable resistor. The real-time variation of conductance, which is the inverse of the resistance, is calculated.
Skin Conductance increases or decreases proportionally. Skin conductance, galvanic skin response and electro-dermal (EDR) are different terms for similar physiological measures.
Skin Conductance is considered to be a function of sweat gland activity and skin pore size, both of which are controlled by the sympathetic nervous system. Sweat glands are activated when the sympathetix nervous system is aroused in response to stress or anxiety. As sweat is produced, the skin's capacity to conduct current is enhanced and the measured conductance is increased.
The skin conductance sensor has two short leads that extend from the circuit box. At the end of each lead is a sensor snap similar to those on the extender cables. The GSR sensor uses two replaceable sensors that are sewn inside a hook and loop style straps.
The sensor strap must be fastened around the finger tightly enough so the sensor surface is in contact with the finger pad but not so tightly that it limits blood circulation. No conductive paste should be used on the sensors. Remember to clean the sensors with an alcohol wipe between clients. The Ag/AG/CL sensor snaps should be replaced after about 50 uses or when wear is apparent. Wear is apparent when the dark gray finish shows signs of a silvery color, like a well used silver coin.