Found this

[colin563]

not sure if this is the correct place to post

i found this on ebay
 http://cgi.ebay.co.uk/DIGITAL-RED-LED-PANEL-FREQUENCY-SPEED-METER-TACHOMETER_W0QQitemZ250488181400QQcmdZViewItemQQptZUK_BOI_Electrical_Test_Measurement_Equipment_ET?hash=item3a52425298&_trksid=p3286.c0.m14

it must be of use in a lathe or mill just need a sensor the selers have sent me a pdf file on this

they have not got a sensor for it ive searched ebay and im not sure what type of sensor i would need

my electronics info is about as good as my model engineering not a lot

it might be a cheap and easy way of adding a tacho to our machines

hope someone can come up with a cheap sensor to work with this

if anybody wants the pdf file on this please pm your email addy for me to send it


thanks colin

[John Hill]

Colin, it says one of the inputs is square wave and you get a form of square wave just by switching a switch off and on so I expect all that would be needed for a sensor would be a magnetic switch (as sold for house security systems) and a magnet stuck to the back of the chuck.