anyone else like using 'older' test gear like AVO meters?

[carbonzit]

Both have their place in the workshop, but there really isn't anything like watching that needle swing across the face of a dial, on the case of wiggling needles, i always admired the old style VU meters on the front of older style hi fi units, leds just don't cut it.

Amen to that, brother.

Just to keep things in perspective, there certainly are situations where an older analog meter just won't do. Anytime a high input impedance is needed, in order not to overload the circuit being measured, the tens of megohms input of a DMM is clearly superior to the tens (or hundreds) of Kohms for the best of analog meters.

Other than that, old-school mechanical meters, with their D'Arsonval movements, give a much clearer indication of magnitude than a bunch of LED or LCD digits.

By the way, I neglected to mention the "hybrid" that actually satisfies both requirements (easy-to-read analog display and high input impedance): the old-fashioned VTVM (or a newer solid-state meter with FET front end). This is the best of both worlds, and I highly recommend getting one.

 

[tvtech]

Amen to that, brother.

Just to keep things in perspective, there certainly are situations where an older analog meter just won't do. Anytime a high input impedance is needed, in order not to overload the circuit being measured, the tens of megohms input of a DMM is clearly superior to the tens (or hundreds) of Kohms for the best of analog meters.

The G2 or screen voltage on a TV cannot be read accurately with a digital meter. Here is why.

The average digital meter has a fixed input impedance of around 10 Meg. No matter how high the voltage you are trying to measure is.
The analogue on the other hand has a Ohms Per Volt rating. So at a G2 voltage of say 800V the Digital still has its 10 Meg input impedance...whilst even a basic 20Kohm per volt analogue has an input impedance of 16Meg at this voltage so it loads the circuit less and gives a more accurate reading.

I use a YEW 100K per volt analogue meter. At 800V its input impedance is 80 Meg. Eight times more than the average digital. It reads the G2 accurately.

Cheers,
Tv Tech

 

[carbonzit]

The G2 or screen voltage on a TV cannot be read accurately with a digital meter. Here is why.

The average digital meter has a fixed input impedance of around 10 Meg. No matter how high the voltage you are trying to measure is.
The analogue on the other hand has a Ohms Per Volt rating. So at a G2 voltage of say 800V the Digital still has its 10 Meg input impedance...whilst even a basic 20Kohm per volt analogue has an input impedance of 16Meg at this voltage so it loads the circuit less and gives a more accurate reading.

Interesting. Measuring high voltage seems to be another in the "plus" column for analog meters.

 

[Neil Groves]

i really like these meters, i just checked them out on ebay and they are within my price range, so just for old times sake i will likely end up buying one to play with.

**broken link removed**

Neil.

 

[carbonzit]

Kewl: three separate ohm-range zero knobs. With my el cheapo VOM (Radio Shack--ugh), you have to readjust the control every time you switch resistance ranges.

 

[stk2008]

I have an AVO meter some one can have for a £5 just to cover the fuel of when I picked it up you will need to collect it though I live in Oxford UK.

i dont know if it works or if its complete but it may be of use

looks like this

https://www.radiomuseum.org/images/radio/avo_ltd_london/all_wave_oscillator_367567.jpg

 

[The Electrician]

So at a G2 voltage of say 800V the Digital still has its 10 Meg input impedance...whilst even a basic 20Kohm per volt analogue has an input impedance of 16Meg at this voltage so it loads the circuit less and gives a more accurate reading.

I use a YEW 100K per volt analogue meter. At 800V its input impedance is 80 Meg. Eight times more than the average digital.

You seem to have a fundamental misunderstanding, tvtech. The input impedance of a VOM in not equal to to the ohms/per volt characteristic multiplied by the voltage you are measuring; It's the ohms/per volt times the range you have selected on the meter.

For example, it would be likely that you would be using a 1000 volt range to measure 800 volts. Then the meter input impedance of your YEW would be 100 megohms, not 80 megohms.

 

[tvtech]

You seem to have a fundamental misunderstanding, tvtech. The input impedance of a VOM in not equal to to the ohms/per volt characteristic multiplied by the voltage you are measuring; It's the ohms/per volt times the range you have selected on the meter

No misunderstandings here. The YEW is not a VOM. It is a 100Kohm per Volt analogue Taut Band meter

Been in service for around 20 Years now. And still going strong. Good stuff.

Made by YOKOGAWA in Japan. Best of the best bar none.

Live and learn

Cheers,
Tv Tech

 

[stk2008]

Yeah what he said? I have no idea what you are talking about hahahahahaha.

Any ways me offer still stands on that AVO thing I have I will take pics of it actually and post them tomorrow some time.

 

[carbonzit]

You seem to have a fundamental misunderstanding, tvtech. The input impedance of a VOM in not equal to to the ohms/per volt characteristic multiplied by the voltage you are measuring; It's the ohms/per volt times the range you have selected on the meter.

For example, it would be likely that you would be using a 1000 volt range to measure 800 volts. Then the meter input impedance of your YEW would be 100 megohms, not 80 megohms.

No misunderstandings here. The YEW is not a VOM. It is a 100Kohm per Volt analogue Taut Band meter

But it's still a VOM, or really the equivalent of a VOM. No amplifiers (vacuum tube or solid state) inside, right? Just a meter movement and resistors, diodes and such, correct? That's a VOM.

Beside, the error that was pointed out is in your favor (i.e., the input impedance of the meter is even higher than what you said), so you should be happy. Your point was made.

 

[The Electrician]

No misunderstandings here. The YEW is not a VOM. It is a 100Kohm per Volt analogue Taut Band meter

Here in the U.S., VOM has meant an analog meter for many decades; DVM refers to a digital meter and VTVM means vacuum tube voltmeter..

I was referring specifically to your YEW analog meter, and you apparently do have the misunderstanding I explained.

Been in service for around 20 Years now. And still going strong. Good stuff.

Made by YOKOGAWA in Japan. Best of the best bar none.

Live and learn

Cheers,
Tv Tech

I've had one of these for 50 years:
**broken link removed**

It's a 200k ohms/volt taut band meter, at least as good as your YEW.

 

[carbonzit]

So, collecting some terms for the sake of reducing confusion:

• VOM = volt-ohm-milliammeter
• AVO = Amp-volt-ohmmeter
• DMM = digital multimeter
• DVM = digital voltmeter
• VTVM = vacuum-tube voltmeter

Any additions or corrections?

(By the way, all except DMM and DVM are analog)

 

[ghostman11]

i might well be interested in the AVO i have a real soft spot for them. the thing i realy like is a old weastone bridge! one the very old brass type in a nice wooden case but it would never get used so not a huge amount of use getting myself one!

 

[Neil Groves]

But think of the huge amount of pleasure and satisfaction you'd get from looking at it parked up on the shelf in your workshop....or even in the livingroom above the telly!

 

[squishy36]

Any additions or corrections?

I built some Heathkit VOMs in the 60's and VOM back then always stood for "voltmeter - ohmmeter - milliammeter". I also bought a little Triplett VOM (model 310) in the 70's and it had the same abbreviation in the manual.

 

[tvtech]

Thanks guys....nice thread this.

My terminology is not always spot on anymore. I only have experience to share.

Cheers,
TV Tech

 

[Reloadron]

For those who have some old gear and lack the now hard to find manuals and schematics a great source is The Boat Anchor Manual Archive. The link is to a mirror site. I linked to a mirror because "The main BAMA site is down due to major repairs and upgrades at sbc.edu. A notice will be placed here when they are completed. (9/17/2009)".

Anyway, BAMA has come in handy many times for me on older test equipment as well as assorted radios and other things.

Most of the files are .pdf but there are also .djvu files for download. For these you will need a .djvu reader which can be found here.

Ron

 

[ghostman11]

i used the boat anchor a few times but couldnt find the manuals i wanted to repair a SCOPE i did find them eventualy tho, i will have a dig around on the comp and post the links i used to others sites like BAMA there is about 4 i used so between them you can find just about anything!!!
one other thing if your repairing any kind of HP or Agligent stuff then joing the HP repair group at yahoo is a must!! its a very active group very very friendly, with a karge knowledgable membership that can provide just about any assistance you need to repair a HP machine, at the mo they are helping me to repair a HP 16500C Logic analyzer, i am just waiting for the PSU to arrive now wich has come from the states. then it should be good to go very much looking forward to putting the beast through it's paces! a great machine i got for £50!!!!!!!

 

[Reloadron]

Hi Ya Ghostman

While we have a section devoted to "Datasheets, Manuals or Parts" it might be a good idea to propose to the staff a sticky in that section listing the sites like BAMA and the ones you mention. Sort of a centralized collection of links to manuals and such.

Ron

 

[ghostman11]

great idea Ron! i am sure there are loads of members that have discovered links to useful manuals, some of them are pretty hard to find, i looked for around 3 months to get a gould 4066 manual for the schematics, eventualy i found one on a obscure FTP site