[R-390] OT:Help with AN/URM-223 (ME-297) Batteries ?

[Roy Morgan]

At 12:29 PM 9/15/2002 -0500, Michael Melland wrote:
>I just received a NIB AN/USM-223  (ME-297) FET multimeter.
>  ... there is another mod to allow use of ordinary alkaline AA cells.

Mike,

The mercury cells, or whatever you substitute runs ONLY the OHMS 
function..there is an FET amplfier used only in that function.

The biggest trouble in using AAA cells is where to put them.

The meter is NOT a FET input multimeter.  The meter movement is a high 
sensitvity one and so it will not load the circuit under test in the way 
the older 1000 ohms per volt units did.

>Anyone know what  I need to do to use the Energizer 523's or AA's ?

  I suggest you find a nice way to include them inside the case, and forget 
the problem.. Just solder them together, wrap with tape and stuff them in 
there.

There was a mod done to one URM-223 I have here to add a new test jack to 
the foont panel to allow sucessful testing of diodes.  One of the resistors 
inside is split into two parts and it appllies a larger than normal voltage 
to the diode under test so silicon diodes conduct in the forward direction.

Roy



Roy Morgan
K1LKY since 1959
7130 Panorama Drive, Derwood MD 20855
301-330-8828 home .... 301-975-3254 work
roy.morgan@nist.gov