Using Test Lamps ... DON"T

["Matthew Dooher" <matthew.dooher@xxxxxxxxxxxxxxxxxxxx>]

>Len wrote:
>A very simple automotive tester is a 12 volt lamp and a pair of clip leads.
>To check for ground, put one side of the lamp at a known 12V source, and
the
>other on the suspected "ground." The lamp will light brightly if the ground
>is good, dimly or not at all if the ground is poor, ie, needs cleaning. Any
>12 V lamp will work; I use an old license plate light and wiring harness,
>with a pair of alligator clips on the leads. Cheap and effective!
>
>Be very careful when using a light bulb to test for voltages etc. In fact I
>would say never do it!!!
>If you connect the to the output of an electronic circuit that is only
>designed for say 100mA (almost all Alfa control units have some of these)
>and the poor thing tries to supply say a 10 watt lamp (800mA) you will need
>to buy a new control unit!!
>It really is worth spending a few dollars and buying yourself a cheap
>digital multimeter.
>
>
>Matthew Dooher
>Electronics Tech
>Zoology Department
>University of Otago, New Zealand
>Phone 	+64 3 479-7968
>Fax	+64 3 479-7584
>E- mail 	matthew.dooher@domain.elided
>http://www.otago.ac.nz/Zoology/staff/md.html
>

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