wearing out mechanical D'Arsonval movements?

[eccerr0r]

I was wondering if it's possible/has anyone been able to wear out the bearings of a mechanical meter purely by using it?

I suspect that connecting an AC voltage to a DC meter will vibrate it fast but does not do much movement, but what about a 1Hz source or something like that, would it cause enough wear over time to cause a D'Arsonval movement to wear out and break/become inaccurate?

[redwire]

Re: wearing out mechanical D'Arsonval movements?

There's many different types and quality for analog panel meters. I've never seen one really wear out, although I have one edge-wise from a trucker's CB radio that got sticky, I think damaged from vibration. It's a Taiwan cheap build.
Better, older meters used sapphire jewel for the pivot but I think friction-less taut-band is used nowadays.

"Conventional pivot-and-jewel meters often required bearing replacement after less than one million cycles."
"... no movement deterioration was encountered on the taut-band meters after 50 million full-scale oscillations."

"Particularly severe service conditions have demonstrated the stamina of the taut-band design in the field. One railroad reported that pivot-and-jewel ammeters on diesel locomotives required frequent repair, with overhaul and recalibration typically after eight months. Occasionally servicing was needed after only 30 days. Taut-band instruments in this same service for four years required calibration adjustment only twice, with no parts replacement."
https://www.weschler.com/blog/the-ta...-analog-meter/

If you have AC wiggling the needle, it gets smoothed out by the needle and mech mass as well as the shorted-turn damping on the moving coil. The meter's rectifier gives 2X freq. ripple so say 120Hz you can hear it.

[eccerr0r]

Re: wearing out mechanical D'Arsonval movements?

I suppose that damage from shaking the whole unit or other environmental damage (dirt, water, oils, dropping, etc.) shouldn't count towards its "best case" longevity - assume that it's in a clean, fixed location environment. But it seems like these should last a very long time, wondering if springs break after use a significant amount of use or not, also the difference between fast (take less than 1 second to stabilize) and slow (possibly take 2-3 seconds to stabilize) settling meters...

[redwire]

Re: wearing out mechanical D'Arsonval movements?

I think a panel meter's enemy is shock and vibration. The springs are coil like clock springs or taut-band and seem to not fatigue fail.
In the old days, for shipping, you shorted a panel meter out with a piece of wire to prevent the needle from banging around, block generator-action.
The slow meters seem to have heavier mech to dampen out noisy signals. There is a counter-weight as well. It depends on the meter's sensitivity as lower FSD say 100uA movements are wimpy compared to say 1mA which have more torque.
I have some old Simpson VU 142 4" meters and they are super fast, very lightweight needle.