differential voltmeter!

[Structo]

I built that Heathkit VTVM when I was a kid.

Worked great for years, don't recall what happened to it.

[triode3]

My goal is to measure the two push-pull signals (after PI) to set the same amplitude!

If that is the goal: Don't worry about all of this high input impedance, analog meter with a center zero stuff... get a used two channel Tek oscilloscope. Your worries of loading the PI will go away when you think about it (the scope will equally load each side, so it does not matter, if you are REALLY concerned about that, factor in the load and adjust the voltage accordingly)...

Still, if you are looking to balance two AC signals out of a PI, you want to just grab a two channel scope. It will get you so close to perfect balance... you could not ask for more (or do it for less, you don't need a "great" scope for this).

Besides, you can do a lot with a scope in the shop. If you are DIY, you should own one already

[tubelectron]

Sergio,

I'll be to old school, but attached to analog equipment

Me too... But that doesn't mean that we are old school !

For me is the best way to this measurement!

A good DVM can really challenge it - I own a FLUKE 87-III and a 87-V, but I must admit that these excellent instruments are not cheap...

Structo,

I built that Heathkit VTVM when I was a kid. Worked great for years, don't recall what happened to it.

Oh, I am planning to buy one, or even design and built it like when I was a kid - but better finished...

A+!

[sergio]

I have a old Fluke75!

[tubelectron]

I have a old Fluke75!

As far as I remember the FL-75 is not true RMS, but has a bandwith of 50Hz to 1KHz, and an input impedance at least equal to 10M, so if you set your generator at 400Hz, it would be convenient for a proper balance.

Nonetheless, I also like - and use - analogic test equipment :

[img:640:480]http://img11.hostingpics.net/pics/223562IMG7933.jpg[/img]
[img:640:480]http://img11.hostingpics.net/pics/206832IMG7944.jpg[/img]
[img:480:640]http://img11.hostingpics.net/pics/376594IMG7936.jpg[/img]

But a VTVM is missing... You gave me the idea to find or built one again !

A+!

[tubelectron]

Hello,

No missing VTVM anymore : I have 3 of them in my collection now...

[img:436:640]http://img15.hostingpics.net/pics/125427HKV61.jpg[/img][img:425:640]http://img15.hostingpics.net/pics/438899PACOV701.jpg[/img][img:480:640]http://img15.hostingpics.net/pics/938759LMV851.jpg[/img]

A+!