"Jeff Liebermann" wrote in message
...
On Mon, 1 Jul 2013 21:18:05 -0700 (PDT), Peter Easthope
wrote:

I have a Sanwa BX-505 analogue multimeter where the needle wavers and can
not be zeroed on the x1, x10 and x1k scales. Zeroing is possible on the
x10k scale. The ohmeter is really an electromagnetic voltmeter connected
in a circuit with dry cell, resistor, zeroing potentiometer, leads and a
subject resistance.

Scans of the relevant pages from the manual are here.
http://carnot.yi.org/SanwaBX505Manual.jpg

What is the cause of this behavior?

In order of probability:

1. Dirty battery contacts. Clean the contacts and possibly replace
the battery.

2. Dirty test probe contacts, broken test probe wires, corroded test
probe tip. Clean or replace.

3. Dirty rotary switch. Spray with a small amount of contact
cleaner.

4. Dirty fuse contacts or bad fuse. Clean and/or replace fuse.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558



What he said.

I would only add that pushing, poking, tapping around etc while you are
looking around inside might help reveal the one or more bad connections that
might be there.

Also, since these problems tend to be pretty intermittent, you might think
it is fixed, only to recur later, so don't give up after one or two failed
tries, you'll fix it soon enough if you keep trying.

I have a Simpson 635 and a 270 series 2 that have had similar problems, and
a Fluke 8840A which also had issues with the low range ohms.

When somewhat more current is required, as in a Rx1 or Rx10 low ohms
function, poor connections become a much larger percentage of the total
circuit resistance.

Speaking of which, for troubleshooting, one trick would be to remove the
battery, short across those terminals, and measure the total resistance
through your lead wires and through the meter itself using another
multimeter. Meanwhile, the aforementioned pushing, poking, etc might show up
the culprit on the other meter.

Have fun!

Mark Z.

Mark Z.