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Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Alright, long story short I've reached a point where one of these would be dang useful, since there is little information out there about building them and they are REALLY expensive, I come here.
So, I start with a 10 volt DC meter. Then add a rectifier, calibrate, add switch, and bam. It measures AC and DC.
Then, add a 10:1 voltage divider, so it measures 100 volts. Then, add a 100:1 voltage divider (or a 10:1 on top of the existing 10:1). 1000V Then, add a 1000:1 I can measure 10KV Then a 10000:1, I can measure 100 KV.
With a rotary switch to select one. Probably under oil.
Basically I end up with a GIGANTIC 1.21 GIGA OHM (not sure what resistance actually) resistor string tapped at various points, and a rectifier for measuring AC.
So, does this sound do-able? Does anybody have any advice, words or wisdom, or anything that would help out with this at all?
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
For DC, a simple voltage divider will do; you can get cheap probes on Ebay for $20. Its much much much harder for AC; you'll need a capacitative divider.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
that sounds like it should work. I'd make sure the resistors are placed between the hv and the rotary switch (duh), to never touch the rotary switch when measuring, have really high value resistors, and at least double the necessary insulation on everything that isn't submerged in oil.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
magnet18 wrote ...
Alright, long story short I've reached a point where one of these would be dang useful, since there is little information out there about building them and they are REALLY expensive, I come here.
So, I start with a 10 volt DC meter. Then add a rectifier, calibrate, add switch, and bam. It measures AC and DC.
Then, add a 10:1 voltage divider, so it measures 100 volts. Then, add a 100:1 voltage divider (or a 10:1 on top of the existing 10:1). 1000V Then, add a 1000:1 I can measure 10KV Then a 10000:1, I can measure 100 KV.
With a rotary switch to select one. Probably under oil.
Basically I end up with a GIGANTIC 1.21 GIGA OHM (not sure what resistance actually) resistor string tapped at various points, and a rectifier for measuring AC.
So, does this sound do-able? Does anybody have any advice, words or wisdom, or anything that would help out with this at all?
You have much to learn young one!
magnet18 wrote ...
So, I start with a 10 volt DC meter. Then add a rectifier, calibrate, add switch, and bam. It measures AC and DC.
youll need a True RMS meter not a normal RMS meter, and even then this type your suggesting only works for sine waves at 1kHz or less. Youll learn just like i did.
A few points ill give you... 1) HVDC is easy to measure, but only resistive division works well. 2) HVAC is difficult HVHF is even more difficult. 3) A HV sine wave at 60 Hz can be sort of measured with accuracy if a known set up is used and calibrated wisley. 4) Prepare for co$t, prepare for fires, explosions and failures. 5) Always use your cheap DMM and O-scope first, dont blow-out your best one on something that hasnt been proven yet. 6) Stay below the Giga-Ohm level unless your measuring 100kV or more, 100-600M ohms is typical for 10-60kV, if you plan to use the internal resistance of a DMM, then youll have to use GOhm value resistors, but youll be more prone to errors due to light current loading. (Ive even picked up radio waves!)
This covers most of what i can advise you on above and below... try not to get killed too.
HV Flyback Bench Top Power Supply for Lab. HV voltage probe for O-scope, ( DEVELOPEMENT ) Grooved Bobbins For Segmented Windings Calculating Field Intensity at Edges of Cap Plates. 2 Channel High Voltage Oscilloscope Probe. NST HV measurement (True RMS error! ,Realized 6/20/2011) HV Diode making Mearsuring HV resistors to high accurracy HV resistors, Project Pots and HV measurements About Bio-Oils for HFHV Transformers. Capacitive Voltage divider, for O-scopes (10,000:1) Learning from North Star HV probes...
I am currently re-reading everything Proud Mary and i have discussed reguarding the "Park Resistor", for the device below...
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