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GSR Device
(Galvano Skin Response) |
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The GSR is a skin galvanometer, similar to those used in giving lie detector tests. It is also called E-Meter is about ten inches by six inches by two inches and its appearance was described by one reporter as a "cross between a car speedometer and a practical joker's electric shock machine.". The device doesn't actually delivers any shocks. The subject holds in his hands two tin soup cans, which are linked to the electrical apparatus. A needle on the apparatus registers changes in the electrical resistance of the subject's skin. A person asks questions of the subject, and the movement of the needle is apparently used as a check of the emotional reaction to the questions. According to complex rules and procedures set out in some publications, the person can interpret the movements of the needle after certain prescribed questions are asked, and use them in diagnosing the mental and spiritual condition of the subject |
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The diodes are any silicon signal diode.
The LM385 should be a 1.26 volt low power version.
The circuit is powered by 3 AA or AAA cells giving 4.5 volts. The circuit can be used for 1 or 2 meter movements. If one just uses 1 meter then TR2 is omitted and the high end of the TA pot goes to the point marked TA3. For a dual dial meter a multiturn pot can be used. If a 3 turn pot is available then connect the high end to TA3. If only 10 turn is available then try TA3 and TA4 to see which works best for you. The TA pot should be 20k wirewound such as Bourns 3590S-2-203 and the sensitivity pot 50k. For normal use with 2 cans SW2 can be shorted. If one wants automatic retrimming for solo cans or fingertip electrodes then switch in values of 22k and 39k respectively. |
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The voltage reference for the bridge circuit is simplified. The meter biasing has been adjusted to use a standard 0 - 100�A meter. The circuit now uses a readily available LM324 op amp rather than the more expensive and sometimes hard to obtain OP420. The circuit includes amplification for the meter speed making it possible to use an off-the-shelf movement rather than a custom made high speed one. |
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Click Here for Board Layout |
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Back to Electronic Components and Projects |
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(c) 2005 Juriaan Massenza - All rights reserved. |
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