Archive of the former Yahoo!Groups mailing list: MOTM

Hi David n All !

A dvm needs to a complete circuit to make a valid measurement, so
consequently a "hanging probes" readout is meaningless .

If you short the terminals together, what happens ?

Measure the voltage of your power supply : does it give the pos and
neg 15V ? Take a fresh battery, should read someting like 1.60 to
1.50 V . All these measurements done on DC V of course . Check the
Ohms range by measuring a resistor . Is the reading about right
(take the tolerance into consideration : 5%, 1%) ? AC can be tested
by measuring your home supply . Careful with those ranges tho :), if
not autoranging that is .

Measuring low Ohm values with an analogue multimeter and an older
battery is good fun tho, the needle will never stabilise :)
(treasuring a 25 jear old Novotest bought new, then ... ;-) )

A useful addition to any kit is some means to temporarily clamp the
dvm inputs to the object . I'm using Hirschmann Kleps for this
purpose, a bit dear, but good quality . Some croc clips could work
too . But watch out for shorts . Also, make sure you have good
contact . The test points should be sharp, so they can pierce
oxidation . The braid on the RG cables is dull, and solders not too
well (lucky for us, they come pre-tinned :) ), this might give
unreliable measurements . Stick the point in a (shiny)solder joint,
should be ok then . With crocs wiggele the jaws a bit, so the teeth
pierce the oxide, Kleps same thing, get a steady readout before you
start tweaking .

A good thing to have are those multicoloured twin croc connects .
These should be checked after some years use though, as the leads
used are generally of inferior quality, and break at the croc, giving
unreliabe results then .

Have been thinking of this before, but making up a few test leads,
say dvm to jack (ground and signal) should be useful too .

Hope some of this helps .


Keep 'em oscillating :)


Hugo
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