Chris:
A DVM has relatively high input impedance and will pick up stray 60 Hz
and other things floating around (AM broadcast, perhaps) when the leads
are open. In essence, the leads act like a small dipole receiving antenna.
Short the leads together and it should read a lot closer to zero, unless
you live next door to a substation or a 50 KW AM broadcast transmitter.
(You can think of this as converting the leads to a loop antenna, which
has a lot less pickup than a dipole.)
Thus, the behavior you see is normal.
Jack K8ZOA
www.cliftonlaboratories.com
Koaps wrote:
Hello all,
I had a question about using a digital multimeter for
AC millivolt measures.
I have a radio shack 24-range DMM and when I set it to
mV it never seems to go to zero, its constantly
counting numbers from 30-100 mV with the leads not
connected to anything.
If I change the range to .000 V it will show around
.020 to .009 with the leads not connected to anything.
When I tested U1 pin 1 and U3 pin 6 on my KX1 on the
.000 V range I got .000, is this an ok measurement or
is my DMM too screwy to use for AC mV measures?
All the DC and resistance measurements with it seemed
ok.
thanks,
-Chris
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