how to make a DVA adapter for multimeter

Texasmark

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Re: how to make a DVA adapter for multimeter

250 V is too low in theory because you will be applying around 300V or more to it. It might work awhile if you are lucky, but it is teetering on the edge. Like driving a ten ton truck across a bridge rated for 9.5 tons. Might make it if you hold your breath. On the other hand, a cap rated for 600V is better yet.

Funny this popped up today. Several days ago I was looking for this adapter so my thanks F_R for your comprehensive input.

I became interested in this device as my Merc manual lists CDI tests requiring a DVA/DVM and lists a Merc part number (91-99750 which has been upgraded since the manual was published to the current number 91-99750A1). The one listed is a ESI brand. I got curious as to what it was, before I thought about what it was used for, and started investigating.

Upon investigating, I found that you can buy an adapter for $25 from D3 Instruments, P/N ESI-640 for $25. [(941) 538-7775] or the whole meter with adapter on this site for $101 with free shipping (current special). One thing the meter has is a special DVA scale.

So that brings up yet another question and that is what is the difference between this scale and the DCV scale as once you rectify and store pulses, you have a capacitor charged to a rather high (could be as high as 400V per my serv manual) DC voltage....so the 600DCV capacitor rating F-R mentioned is definitely necessary.
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Once I realized that you were trying to measure trigger pulses of maybe 1 micro second duration with a dead time of 1 milli second (at 1000 rpm) it seemed that rectification and storage was the only way to accomplish this....and you needed something (the resistor) to keep the charge on the cap from rising to the peak and just sitting there....had to keep it bled off.

The only question left was what size C for a reasonable charge time and what sized bleeder for a reasonable discharge time without affecting the peak stored value. You (or bktheking) solved that problem for me.

Not mentioned in your fine piece of work F_R, (or I missed it) is what scale on your multimeter you use. Since it is DCV that's what it will be and the voltage range will be 1000......I just wonder why ESI thought it necessary to add a DVA scale? Possibly to up their profits by selling a fully functional multimeter with the adapter and quadrupling their bucks on the sale. Who knows.
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One final note. I personally would up the Diode's PIV rating to 1kv as my Merc serv manual is expecting to have a reading as high as 400v and I don't want a diode rated right at the max voltage I am anticipating. You can still use a low current device. As I recall, you can get a 1kv diode in that 4000 series of diodes that bk specified...I forget the number; been retired 6 years now but it's at the high end of the series.

Thanks again,

Mark
 

bktheking

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Re: how to make a DVA adapter for multimeter

I just called my local electronics shop, the highest they stock is 450V, I've asked to see if a 600V is available.
 

bktheking

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Re: how to make a DVA adapter for multimeter

He called 2 suppliers, the highest 2.2 they can get is 450V.
 

ezeke

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Re: how to make a DVA adapter for multimeter

He called 2 suppliers, the highest 2.2 they can get is 450V.

The part listed in the original document (Parts Express) is 450V - their part # 020-1462.
 

F_R

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Re: how to make a DVA adapter for multimeter

So that brings up yet another question and that is what is the difference between this scale and the DCV scale as once you rectify and store pulses, you have a capacitor charged to a rather high (could be as high as 400V per my serv manual) DC voltage....so the 600DCV capacitor rating F-R mentioned is definitely necessary.
---------------
Once I realized that you were trying to measure trigger pulses of maybe 1 micro second duration with a dead time of 1 milli second (at 1000 rpm) it seemed that rectification and storage was the only way to accomplish this....and you needed something (the resistor) to keep the charge on the cap from rising to the peak and just sitting there....had to keep it bled off.

The only question left was what size C for a reasonable charge time and what sized bleeder for a reasonable discharge time without affecting the peak stored value. You (or bktheking) solved that problem for me.

Not mentioned in your fine piece of work F_R, (or I missed it) is what scale on your multimeter you use. Since it is DCV that's what it will be and the voltage range will be 1000......I just wonder why ESI thought it necessary to add a DVA scale? Possibly to up their profits by selling a fully functional multimeter with the adapter and quadrupling their bucks on the sale. Who knows.
------------
One final note. I personally would up the Diode's PIV rating to 1kv as my Merc serv manual is expecting to have a reading as high as 400v and I don't want a diode rated right at the max voltage I am anticipating. You can still use a low current device. As I recall, you can get a 1kv diode in that 4000 series of diodes that bk specified...I forget the number; been retired 6 years now but it's at the high end of the series.

Thanks again,

Mark

Good question, I don't know why they feel a special scale is needed. Seems like you have it all figured out though. Yes those diodes are (or at least were) common and readilly available at 1000V. Cheap too.
 

bktheking

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Re: how to make a DVA adapter for multimeter

Depends where you live, here in the great white north it would be $25+ shipping + duty, next thing you know your $25 DVA costs $60. I agree, free shipping and living in the US i'd do it in a second.
 

Texasmark

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Re: how to make a DVA adapter for multimeter

What am I missing? Why would anyone make a DVA when you can buy one for $25.00? I have the skills and equipment to make one, but why? All the screwing around and cost to find the right cap, etc.! See here:
http://www.usatoolwarehouse.com/usatoolwarehouse/ESI-640.html

I'll tell you why: Because it is too cold for me to go fishing. LOL So I am digging around in the scrap box of old electronic parts and seeing what I have that I can Kluge up and build one. I have been messing with this for 2 days now and it keeps the mind active. I've found parts socked away I haven't touched for 10 years......and yes in 10 years, carbon resistors change values (that's not a critical item).....but my glass-metal hermetically sealed cap and glass diodes don't age like that.

On the buy one for $25, as you said, in a heartbeat and may still do it, but for now I am fooling around and I think I have acquired enough parts....just need a box to put it in.....may just cut up some slick plastic, put all the parts in it and fill it with epoxy then peel off the mold.

I even dug out my old D'Arsonval mechanically metered VOM to attach it to so that I could get the averaging effect of the mechanical movement folks have been mentioning. Obviously it follows the average voltage value and doesn't run numbers all over the place like the present day digital dudes do........course they definitely have their place in my shop for steady state readings; especially in measuring battery voltages rather than using a hydrometer to measure charge level.

I don't currently need one (whoope) but I have had CDI problems in the past (thermal in nature) and if I have them again, I'll be ready.

So, while I am blabing for those interested in following, time constant (TC) for the circuit = RC, and as you electronics guru's involved in this know that full charge/discharge is 5 TC. I don't have a 2.2 uf 600V cap and 1 Mohm R, but I do have a .47 @ 600VDC cap that will work nicely and I also have a 2.2 Mohm R.

The time constant for this setup is half that of the ones in the other guys tool chest, but since one time constant of this circuit is seconds long, and the pulse/rest ratio of the circuit at 1000 rpm is .001 second (1ms) we are looking at a 200:1 overkill (at 5 TC's) and I have no doubt that the parts I scrounged up will work and I feel sure one could drop sizes significantly and still have enough storage on the C to satisfy the measurements specified in the serv. man.

Geez, we could be doing this for a living.......naw those times are past. This is fun because you don't have to do it.

Thoroughly have enjoyed this and it has been beneficial for me too; learned what DVA means and will soon have my very own DVA adapter. Now where's the epoxy?

Mark
 

bktheking

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Re: how to make a DVA adapter for multimeter

All fixed, diagram and pics and the diode being in the wrong direction (thanks for noticing Texasmark :)), thanks for all the input and corrections. I didn't see the "." between the 2's on the diagram I printed out and didn't check the p# on the list. I tested it again tonight on a small battery and it worked, can't test the powerpack out until it warms up.
 

g6ips3y

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Re: how to make a DVA adapter for multimeter

I went to C&G electronics in Tacoma ,Washington They showed me wich way the Diode and cap go , It works "Thanks" , I built it for the fun of it , I tested the known factor , house hold 120V is 160 to 170 DCV Peak , So I tested the outboard motor , It costed about 30$ for the parts to make 2 . Radio Shack didn't have the High volt parts .
Basically it was a fun project , Any Brainiacs want to post a diagram to build a power pack for a 1976 135 HP Johnson outboard ? I will build it and report ,
It's not too hard , I have built those project mini broadcast radios . The DVA is much simpler , I am a carpenter and can follow a blue print . These projects aren't much harder , Kinda fun to do and read about , As sawing and nailing gets a bit mundane after a couple decades .
THANKS AGAIN FOR POSTING THE BRAIN TEASER DVA PROJECT. But it really wasn't hard .
 

Osage76

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Re: how to make a DVA adapter for multimeter

I currently have a UEI Digital Multimeter model DM383B. http://www.ueitest.com/product-dm383b.html One of the great features is the MAX setting that will hold on display the max voltage during the test. My question is does this perform the same as a peak reading Multimeter or a DVA peak reading multimeter? If not can someone please explain the diffrence. Also I found an "adapter" that is supposed to turn any standard multimeter into a peak reading. http://www.maxrules.com/fixtools640.html
Would this matter on my multimeter as it already has the MAX function?
 

dwco5051

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Re: how to make a DVA adapter for multimeter

I have a UEI 99 and purchased that DVA Adapter about a year ago and it fits into the lead jack holes perfectly. Check around on the internet and you should find the #640 adapter for about 25 buck. I paid about 22 back when I got mine. See http://tools.ntxtools.com/dva-peak-reading-digital-multimeter--list for one for 25.04.

I have used the adapter on a couple of different motors and it works good with my meter.
 

flintcreek

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Re: how to make a DVA adapter for multimeter

Thanks for the links, I stumbled across this thread yesterday and had not found a DVA adapter for less than $50....so I ordered one yesterday...hopefully it will be in soon.

Flintcreek
 

234rick

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Re: how to make a DVA adapter for multimeter

Will these adapters work on a Digital Meter ???
 

wilde1j

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Re: how to make a DVA adapter for multimeter

I don't know why not. It's just an RC network with a diode for catching peaks.
 

Lostfisher

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Re: how to make a DVA adapter for multimeter

I am confused, can someone explain to me the purpose of this device and how it works?
 

wilde1j

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Re: how to make a DVA adapter for multimeter

It catches and retains voltage peaks, which may only be present for a very short time, and otherwise unobservable.
 

Vic.S

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Re: how to make a DVA adapter for multimeter

I am confused, can someone explain to me the purpose of this device and how it works?

A DC volt meter reads the continuous DC voltage ... thats simple.

An AC voltmeter reads what is known as the rms ( root mean square) value. For a sinusoidal wave form that is 0.7 x voltage of the peaks of the wave ( 1/√2 x, to be more precise)

For wave forms that are not sinusoidal it is often relevant to measure the peak voltage directly. Such a time is measuring the peak voltage of the pulses from a CDI power pack going to the HT coils.

For this purpose a peak reading voltmeter is required.
A DVA ( Direct voltage adapter ) can be used to enable a standard multimeter to be used.
 
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