Texasmark
Supreme Mariner
- Joined
- Dec 20, 2005
- Messages
- 14,662
Re: how to make a DVA adapter for multimeter
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
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.
---------------
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
), 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.
