VU meter

[guidoilieff]

hey, I have this thing lying around and wanted to know if i could use it as a vumeter. How can I test it? Thanks

[Groovenut]

I dont know where the pics in the thread went but here's Merlin's thread about a DIY VU meter

http://www.diystompboxes.com/smfforum/index.php?topic=96709.msg840950#msg840950

[Rob Strand]

The way Analog meters work is the deflection is proportional to current.
Full scale can be anything from 50uA to 1mA.

Analog meters that measure voltage, like the battery indicator, have resistor added in series with the meter.   R = V_full scale / I_meter  less the meter impedance.

It is often possible to open-up the meter and remove the resistor.

Off the shelf VU meters have special time characteristics to average the input waveform and often had a rectifier inside the unit.

The thing to note is when you use a normal meter as a VU meter you need to add a peak detector with the correct time attack/release time constants.

http://en.wikipedia.org/wiki/VU_meter

I can't vouch for this circuit specifically but it does show the typical doubling-rectifier and filter cap:
http://www.next.gr/meter-counter/vu-meters/Analogue-VU-meter-l7602.html