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
=