how to make a DVA adapter for multimeter

[jonesg]

Re: how to make a DVA adapter for multimeter

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.

Oh yeh?
Thats all very easy for you to say.

 

[tx1961whaler]

Re: how to make a DVA adapter for multimeter

Oh yeh?
Thats all very easy for you to say.

And to confuse things even more, a peak reading voltmeter is not the same as a DVA. A peak reading digital meter simply has the ability to remember the highest reading that it saw during the measurement period. Most meters do not have the sampling rate to reliably catch the extremely short duration, high voltage peaks in an ignition system. The DVA has a capacitor in the circuit that is charged to the peak value of the input (eventually).

 

[Lostfisher]

Re: how to make a DVA adapter for multimeter

What importance does this device have for the use of outboards. What part of the outboard does this test.

 

[bktheking]

Re: how to make a DVA adapter for multimeter

Powerpack's, timer base, stator- mostly all the high voltage goodies, resistance tests too but you don't need the DVA for those tests.

 

[McGR]

Re: how to make a DVA adapter for multimeter

Troubleshooting Capacitive Discharge ignition systems commonly used on outboards often requires measurement of peak voltages.

Edit.... Looks like BTK beat me to that one...

 

[wilde1j]

Re: how to make a DVA adapter for multimeter

Used to test ignition and charging systems. Description per CDI Electronics:

DVA Explained
DVA stands for Direct Voltage Adapter, which is used to measure peak AC voltage. This type of measurement of AC voltage takes the absolute peak or highest value of the fluctuating AC voltage signal. Peak readings will be substantially higher than standard or RMS AC values and are typically used when testing marine CD (capacitor discharge) ignition systems due to their high variance in frequency as RPM increases and decreases.
An example would be that the typical RMS AC reading of a wall outlet in North America is
120V. However, a DVA measurement of this same AC voltage would reveal that the peak of the AC sine wave is typically between 160-170V.
Some meters are capable of reading DVA or peak voltage pulses. Many ignition system
components produce short AC voltage pulses. A peak-reading analog meter or DVA adapter
plugged into a digital meter captures and holds the peak value of an AC sine wave long enough for the human eye to see it displayed on the meter. A conventional meter is incapable of accurately measuring these short-duration voltage pulses. A peak-reading voltmeter has special circuits that allow the meter to capture the maximum voltage produced during these short duration pulses and display the voltage as DVA or peak voltage. Failure to measure DVA can cause good ignition components to be incorrectly diagnosed as faulty.
The only meters that have built-in peak reading capabilities are analog meters with built-in DVA. Digital meters do not have built-in peak reading capabilities. In order for a digital meter to read peak voltage, one will need a DVA adapter, such as CDI part# 511-9773 or 511-9773NL.
Using a DVA adapter, a digital meter must be set to its DC voltage scale. Peak AC voltage is the measurement, but the DVA adapter has a built-in bridge rectifier, which converts AC to DC. The DC voltage setting on a digital meter is required to accurately read DVA.

 

[AlTn]

Re: how to make a DVA adapter for multimeter

I hope no more than 15% of the final grade will involve DVA in's, out's, and why for's

 

[Fuzzytbay]

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.

Carleton Place Ontario..the great white north........45 degrees 08'35.34"N I think not,....
Thunder Bay Ontario 48degrees 24'56.89N Closer to the GWN...but still not there yet....

Armstrong Ontario 50 degrees18"11.00 N now were getting there.

On the other note, I didn't cost me much more than 25 bucks for a medium grade DVM, not my flukes though that captures peek, but still it should do the job

 

[bktheking]

Re: how to make a DVA adapter for multimeter

It's whiter than Florida

 

[flintcreek]

Re: how to make a DVA adapter for multimeter

Well my DVA adapter came in today, so maybe tomorrow I can try to figure out how to use it...would be great to get my 35 going tomorrow for a trip Saturday to Guntersville. I bought it using the link off this post at USAToolwarehouse.

Thanks,
Flintcreek

 

[Fuzzytbay]

Re: how to make a DVA adapter for multimeter

It's whiter than Florida

So true........

 

[Speedwell69]

Re: how to make a DVA adapter for multimeter

This is the wiring diagram

For the cap that's VDC.

What should the voltage rating be for the 1 megohm resistor.

Thanks

Michael

 

[Vic.S]

Re: how to make a DVA adapter for multimeter

A 2watt 500volt 1 M resistor from Maplin, Unit A, Colchester Retail Park, Sheepen Road would be fine. Only a few pence

Maplin also have the diodes but not AFAIK the capacitor rated at 450v

RS components perhaps.

 

[Speedwell69]

Re: how to make a DVA adapter for multimeter

A 2watt 500volt 1 M resistor from Maplin, Unit A, Colchester Retail Park, Sheepen Road would be fine. Only a few pence

Maplin also have the diodes but not AFAIK the capacitor rated at 450v

RS components perhaps.

Well that's handy as I only live ten minutes from there. Thanks

 

[g6ips3y]

Re: how to make a DVA adapter for multimeter

I am not a pro but . ... In laymans terms ,My info will not be technically correct but generally correct A digital volt meter samples every 3 seconds or something like that. A pulse from the stator ignition coil Is WAY faster than the meter samples , The meter can't capture the voltage surge because the surge is too fast , So the adapter helps capture the voltage surge , Then lets the digital or analog meter measure it .

 

[Dabbler_E]

Re: how to make a DVA adapter for multimeter

Thanks to all you for keeping this thread around.

Thanks to you, I cobbled together a DVA adapter based on these schematics and used it to positively diagnose a bad powerpack.

Iboats rocks in 2 ways: the forums are amazing sources of info, and the powerpack that I ordered on Monday arrived yesterday (Tuesday).

E

 

[surrender]

Re: how to make a DVA adapter for multimeter

So can you8 use a different capacitor like the .47 one someone else suggested? My radio shack only has 2.2 rated to 35VDC.

 

[ezeke]

Re: how to make a DVA adapter for multimeter

Try whatever you want, but don't forget that the original concept DVA designed by Bill Rogers was pretty specific as to what worked.

In the meantime, unless you have a time tested superior design, there is always: http://www.usatoolwarehouse.com/usatoolwarehouse/ESI-640.html

Reference: http://forums.iboats.com/attachment.php?attachmentid=43784&d=1264473219

 

[surrender]

Re: how to make a DVA adapter for multimeter

Another question, So when this contraption is finished you put the test leads from the adapter to the parts your trying to test, crank motor over or run motor(if its running) then remove leads and put test leads from your regular multi meter on DC scale to other ends of homemade adapter to test the voltage the capacitor charged to? Or do you have the homemade adapter plugged into your regular voltmeter set on DC scale and test as you normally would?

One more. When testing for instance the brown wires coming off my stator which is generally considered "positive"? If I use a certain electronic capacitor doesnt it only work in one direction? If that is the case I have to put the red lead to the "positive"wire from the stator, which would it be?

 

[surrender]

Re: how to make a DVA adapter for multimeter

Anyone?