Texasmark
Supreme Mariner
- Joined
- Dec 20, 2005
- Messages
- 14,780
Re: Looking for a DVA Genius
On the "measured a dc voltage and it.................".
You can measure a dc voltage with this and even pull the c and r out of the circuit and still get an accurate reading other than the 0.7V more or less drop across the diode you will loose in measurement accuracy.
This is not a dc measuring critter, you don't even need/use it for measuring dc.
This is a stowage circuit for short duration high voltage pulses with a lot of time between pulses to create a suitable input for a common VOM to read.
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You may hear old timers talk about Vacuum Tube Voltmeters and the Peak Detecting of AC/pulsed voltages. I have an old EICO kit "Peak to Peak" VTVM and after playing with this subject (I even dug it out of mothballs to help me understand just what DVA was and was attempting to do) for 3 days now (on here) I have come to realize that the reason it was what it was advertised to be was because it had a big fat probe that came with it and internal to that probe was the same kind if circuit. The probe was big and fat to accommodate the circuitry....little did I realize that at the time....I hated that big fat thing....1" or so in diameter and 4" or so body length.
The other thing VTVM's had was an input impedance in the 100's of Megohms where a normal VOM had like 20k to 30k ohms per volt. So the VTVM was useful in measuring high impedance circuits where normal VOMs would bleed off the voltage (load down the circuit due to the low input impedance) and cause a measurement error. Course today we have the magnificent DVM/DMM with input impedances as good as or higher than the VTVM of yesteryear so we get our cake and can eat it too......portable highly reliable measuring instruments very economically priced. Yahoo for technology!
Mark
On the "measured a dc voltage and it.................".
You can measure a dc voltage with this and even pull the c and r out of the circuit and still get an accurate reading other than the 0.7V more or less drop across the diode you will loose in measurement accuracy.
This is not a dc measuring critter, you don't even need/use it for measuring dc.
This is a stowage circuit for short duration high voltage pulses with a lot of time between pulses to create a suitable input for a common VOM to read.
---------------
You may hear old timers talk about Vacuum Tube Voltmeters and the Peak Detecting of AC/pulsed voltages. I have an old EICO kit "Peak to Peak" VTVM and after playing with this subject (I even dug it out of mothballs to help me understand just what DVA was and was attempting to do) for 3 days now (on here) I have come to realize that the reason it was what it was advertised to be was because it had a big fat probe that came with it and internal to that probe was the same kind if circuit. The probe was big and fat to accommodate the circuitry....little did I realize that at the time....I hated that big fat thing....1" or so in diameter and 4" or so body length.
The other thing VTVM's had was an input impedance in the 100's of Megohms where a normal VOM had like 20k to 30k ohms per volt. So the VTVM was useful in measuring high impedance circuits where normal VOMs would bleed off the voltage (load down the circuit due to the low input impedance) and cause a measurement error. Course today we have the magnificent DVM/DMM with input impedances as good as or higher than the VTVM of yesteryear so we get our cake and can eat it too......portable highly reliable measuring instruments very economically priced. Yahoo for technology!
Mark
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