# I goofed up and bought the wrong kind of analog meter, but wow, it's veeery sensitive!

#### Hamlet

Joined Jun 10, 2015
327
I thought I was purchasing a 30v meter, but bought a 30A meter instead.
Of course, I don't have any 75mv shunts in the 30A rating, so it's useless.

Dang.

Then, I decided to fool around with it, and see if I could get it to work as
a voltmeter. Thru trial and error, I discovered that 6.07K (6075 ohms) in
series works perfectly to convert this ammeter into a 0-30v voltmeter. This
is great, because the scale reads from 0 to 30. I might have a use for it after all.

Then I put this meter aside, rummaged around, and found a 100uA meter,
and hooked this new meter to a small 2cm coil of wire with perhaps 100 turns. I put
a small neo magnet on the end of a screw driver, and plunged it into the
bobbin of wire, and got the meter to jump about 5% of full scale. Then I
replaced the 100uA meter with my mystery 30A meter. Waving the magnet
in the coil got the needle to jump about 30% of full scale.

At this point, I'm thinking this meter is quite sensitive. I'm feeling better

My next step was to test the ohms, so I briefly touched my dvm to the terminals
on the meter... with a reading 14.5 ohms, the needle deflected about 25%.

My question is this: What is the sensitivity of my meter?
I'm guessing it must be in the uA range? I have little documentation. I got it at ebay.

#### tcmtech

Joined Nov 4, 2013
2,867
My question is this: What is the sensitivity of my meter?
75 millivolts for the one and 100 uA for the other.

#### #12

Joined Nov 30, 2010
18,210
Looks like 5 ma to me.
(4.9265 ma)

#### dannyf

Joined Sep 13, 2015
2,197
What is the sensitivity of my meter?
fairly easy to calculate.

1) 75mv full scale.
2) (30v-75mv) / 6.070k = ~5ma, full scale.

so that's it.

#### R3ctify

Joined Nov 19, 2016
11
I did a bunch of work with my old school analog meter on diagnosing bad LDO's on a vizio 50" Plasma TV and it did the job... SMILES

ch33rs