Modifying a U4324 Multimeter to accept different battery

['LIVEWIRE?']

Something in my 'forgettery' tells me that a 2k resistor has to be fitted to this Russian multimeter in order that a readily available battery can be fitted. Can anyone confirm this, tell me how to go about the mod, and what battery to use, please?

,

[Nickthedentist]

Some info in this old thread, especially post 10, Mike: https://www.vintage-radio.net/forum/...ad.php?t=64987

['LIVEWIRE?']

Thanks, Nick.

[MotorBikeLes]

Years ago I bought the next more upmarket version from Z&I Aero. A very good meter, but at some time I must have sold it on, possibly after buying a nearly new Selectest Super 50 Mk !!.
But I recently came across a U4324 for about a fiver, complete with its manual. Not touched it yet, but the little manual is on the computer desk in front of me right now.
Les.

[stuarth]

Tis I who wrote post 10 on the thread referred to above.

My u4324 still has the same 6V battery from 10 years ago! (hope they're still available)

Still gets used - mostly for checking forward drop and brightness of LEDs

I seems not universally recognised that, although the resistance scale is non-linear, for a normal analogue multimeter, the meter deflection on resistance ranges is linearly proportional to the current through the resistor or diode under test, as it is, in the reverse direction for the voltage across the resistor or diode.

For example, the very simplified circuit of an AVO8 on its middle resistance range is a 1.5V battery, a 2k range resistor and the test terminals in series, with the meter showing the current in this loop.
With the test terminals open circuit, there is zero current in the loop, zero deflection on the meter, and 1.5V across the terminals.
With the terminals shorted, there is a current given by 1.5V/2kohm, and the meter reads full scale, i.e full scale deflection is 0.75mA, and there is of course zero voltage across the terminals.
With 2kohm across the terminals, you get a current of 1.5V/4kohm, ie 0.375mA, 1/2 scale deflection and 0.75 v across the terminals.
Unfortunately, an AVO8 does not have appropriate scales for 0 - 0.75mA, or for 1.5V - 0V, and anyway 1.5V isn't enough to turn on many LEDs.

The U4324 however has a scale with 6 major divisions. With a 6V battery, it can comfortably turn on most (all?) LEDs, its 3 middle resistance ranges of 500ohm, 5k, and 50kohm give full scale currents of 12mA, 1.2mA, and 120uA, and all 3 ranges read 6v to zero for voltage across the terminals, all easily read on a 6 division scale. Thus you can check LED forward voltage and brightness at 3 different current levels.

Well worth a fiver, Les

Stuart

[orbanp1]

Interesting!
The RM page for this analog multimeter clearly shows something like 3 AA batteries as the power source:
https://www.radiomuseum.org/r/maschp...aet_u4324.html
Did they have different versions?

If the meter movement is a taut spring suspension type, like the U4212, U4213, then this meter is not really a low-end multimeter!

Thanks, Peter

[stuarth]

The pictures show the same meter I have. There’s no room in there for 3AA cells, it uses a stack of 3 NiCad button cells. And yes, it it a taut band movement, so no friction. Quite a nice handy compact meter really. Not a match for an AVO 8, but better than a multiminor.

Stuart

[orbanp1]

You are right, that Russian meter does not even get close to the AVO, may be except in the quality of meter movement, but that could be questionable too!

I do have an Univeka Type-147 URAV multimeter, it is built like a tank.
It is a 20 kOhhm/V meter (50uA), and has a taut spring meter movement.
I use it every now and then as it has a 5000VDC range, what present day multimeters do not handle without a HV probe.

Here is a very entertaining description of "dissecting" such an Univeka meter - it had a broken taut spring.
And here is the section about the meter movement.
(Run it through a translator, or just look at the pictures, if you click on them, it shows them in hi res.)

Peter