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Re: [TCML] VDG belt materials



Warning to all:

Be very careful with any meters around a VDG because of dangers from sparks. DMM's are very easy to damage and regular panel meters are too. I always shunt DMM's with 0.1 ufd capacitors even if it makes them slow readings. Panel meters are best protected with a pair of rectifier diodes across the terminals, one with polarity reversed so that the pair conducts in either direction. I had a very valuable 0 to 5 uA panel meter which I blew open with a spark before I found out the danger.

Ed

On 2/4/2016 4:58 PM, doug wrote:
Thanks Derek; The test setup I am using has no top load, and when I take a reading on one of my VDG's I make sure to disconnect the top load on that machine.
Doug

-----Original Message----- From: ExtremeElectronics.co.uk
Sent: Thursday, February 04, 2016 5:08 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] VDG belt materials

Doug,
    From what you have said it is likely to be a charging current of
40uA e.g about 40 on the 50uA scale. I'm guessing that the voltage
reading you were taking would be limited by this current anyway,
therefore the meter position would be the same.

    As long as the meter stays connected, it will be a virtual dead
short. This would be true of the DMM too. Just make sure the device is
discharged when connecting it and on a current scale. I use mine
regularly on my VDG (discharged and no topload) and haven't killed it yet.

    It is a very useful way of comparing setups and materials.

    Cheers
        Derek

On 04-Feb-16 4:18 PM, doug wrote:
Hi Derek; My Multimeter is a, MASTECH-KT7006A/7224, Analog . And I admit to much ignorance in reading it. With the dial set to the 0.5 range on the DCV.A side I get around 40 in the 0 to 50 range, or about 9 in the 0 to 10 range. I get the same reading with the 0.1/50ua setting.
I was just guessing on what the numbers represented.
As Always I appreciate any comments that will help me understand this stuff. It would be nice if someone down at the GEEK GROUP would help me understand my meter but they always seem quite busy when I stop in there. [Message sent].
Thanks Derek, Doug

-----Original Message----- From: ExtremeElectronics.co.uk
Sent: Wednesday, February 03, 2016 7:31 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] VDG belt materials

Doug,
    Ive always found the black belts out perform the others, whether
neoprene, latex or pure rubber, I have no idea why.

    Regarding your measurements, it is usual to quote a charging
current, rather than a voltage, 9MV did make me wonder just how big your
VDG test rig was, until I clicked that it was referring to 9mV. If you
know your meters internal resistance it should be fairly easy to convert
those voltage readings to uA

    Cheers
        Derek



On 03-Feb-16 7:05 PM, doug wrote:
For those interested in VDG generators;
I have been testing different belt materials with my VDG test fixture with some interesting results. The rollers are both PVC, one plain and one with metal coating and are setup for a 4 inch X 40 inch stretched belt. With the belt running at 412 RPM or about 1400 FPS the neoprene belt shows 9 MV, the gum rubber belt 3 MV and the blue exercise belt just over 1 MV. The neoprene and rubber belts are both 1/16 th inch.
Draw your own conclusion but I vote 100% for the black neoprene!
PS; I am not the best at understanding the scales on my multimeter so MV may not be the proper scale, but I think you can understand the difference in readings.
Doug
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