Analog multimeter jacks

[FenderBender]

Hello,

For my birthday, one of my relatives got me an analog multimeter kit. I've always wanted a AVO and it looks like the one I'm going to build up is a pretty good one.

Now, I've used an analog meter but none of them have had this. I've searched through the manual but I'm still confused!

1.) What is this "Output" jack used for? From what I read, if you have an AC signal with a DC offset or something? How would you hook it up?

2.) It looks like you can measure up to 250mA using the "P" and "N" jack. If I wanted to measure up to 10A (which I wouldn't dare! Unfused!), I would have to use the "10+" jack and...."N"? or is it "P"?

3.) What is DCV NULL?

Thanks so much in advance!

[grenert]

3.) What is DCV NULL?

A null meter allows you to balance voltages between the + and - terminals (the two voltage sources have their grounds tied together).  The null setting places the needle at the center of the scale, which then becomes zero.  There is a special blue scale on the dial which shows you the scale for the null function which has a zero in the middle.  See the little centered needle in the picture next to the ohms zero knob?  You would use that to adjust the needle to the middle to prepare for a null measurement.

Have fun building your meter!

[FenderBender]

Thanks for that! I'm sure this is probably all obvious to many of you. Unfortunately, I kind of missed the whole analog meter era.

[Bored@Work]

www.elenco.com/admin_data/pdffiles/m1250.pdf

[FenderBender]

www.elenco.com/admin_data/pdffiles/m1250.pdf

I did read that. Just wondering if someone could elaborate on that whole "Output" thing.

But thank you!

[c4757p]

Looking at the schematic, the "output" jack seems to be AC coupled to the input. Not sure why that would ever be useful, and seems a bit of a safety issue to me. Probing AC, the full voltage will be on that jack with nothing plugged into it, just waiting for something to fall in, at an impedance of about 56K for 60Hz mains, giving a couple of milliamps. Personally I would probably leave out C1 to disable the jack.

[Harvs]

Attached is a cropped screen grab of the schematic diagram in that manual.  The "Output" terminal is nothing more than the pos terminal with a coupling capacitor.

Hence in the manual it talks about measuring a AC component with a DC offset.  So using the "Output" terminal instead of the pos you'll block any DC component, same as AC coupling on a oscilloscope.

God knows why they called it "output".  From the logic in my brain it's got nothing to do with outputting anything.  They could have simply called it AC coupled.

[robrenz]

From the  manual you read 

Output Jack Test (allows measurement of AC voltage when superimposed on a DC voltage.)
1. Plug the red lead into the OUTPUT socket and the black lead into _COM.
2. Set the range switch to the appropriate ACV position. Touch the test leads to the power source and observe
the reading. Then, multiply by the appropriate scale factor.

Translation: Capacitor coupling of signal to eliminate DC component and read only AC component.

[FenderBender]

Hmm well I'll be darned....Don't get why it's called "Output"?

But yeah that's precisely what I thought from reading it, but I didn't think there would be a dedicated jack for it?

[Tube_Dude]

www.elenco.com/admin_data/pdffiles/m1250.pdf

I did read that. Just wondering if someone could elaborate on that whole "Output" thing.

But thank you!

It's all in the pdf...

"Output Jack Test (allows measurement of AC voltage when superimposed on a DC voltage.)
1. Plug the red lead into the OUTPUT socket and the black lead into _COM.
2. Set the range switch to the appropriate ACV position. Touch the test leads to the power source and observe
the reading."

Edit- Robrenz was faster... 

[FenderBender]

Yeah thanks I got it. I was convinced it meant some sort of external output, like to a scope or something?!?! I don't even know.

I'll just shut up now.

Thanks guys.

[Tube_Dude]

Good examples of measurement of AC voltage when superimposed on a DC voltage, is to measure the AC ripple in the main filter capacitors of a DC power supply, amp, DC power rails,....

[FenderBender]

Good examples of measurement of AC voltage when superimposed on a DC voltage, is to measure the AC ripple in the main filter capacitors of a DC power supply, amp, DC power rails,....

Scope works too, but it's a simple neat tool I'd say.

[Tube_Dude]

Scope works too, but it's a simple neat tool I'd say.

Surely scope too, but when you don't have a scope around, or in field conditions...

[T4P]

In the past i had a Sanwa (which they cloned, but it didn't have transistor sockets which they never had) and the 'OUTPUT' jack for connecting to the bases of transistors   

[FenderBender]

Yeah this one seems like a pretty good kit. Quality of the plastic, components and everything is top notch. I'll get some pictures up when I assemble it. Working on fixing up my soldering setup first so I can produce some good results on this.

[mzacharias]

www.elenco.com/admin_data/pdffiles/m1250.pdf

I did read that. Just wondering if someone could elaborate on that whole "Output" thing.

But thank you!

For use at the plate of a tube amp or maybe inside the coupling cap of a single-ended transistor amp. Virtually useless these days. We just use the AC coupled setting on a 'scope for this.

Back then 'scopes were too expensive for most people (good ones anyway).

[FenderBender]

Righto! Thanks.