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Open HV Probe 40kV
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beanflying:

--- Quote from: bd139 on April 23, 2019, 08:14:19 am ---Fluke 7x and 8x meters have variable impedance on each range. It's "around 10-11 meg" and varies from meter to meter and range to range. This is one reason I originally bought a Keysight U1241C as it has constant across all ranges. Shame it otherwise sucked.

--- End quote ---

It is mentioned and tested in W2AEW (Alan's) Youtube video I put up back on page one closest to 10MOhms at the highest range. Also confirmed on the 121GW it is closest to 10MOhms on the highest range. Partly why I opted for 100:1 over 1000:1
vk6zgo:
Not  that it matters with commercial probes, because you always use the highest  range.

Many older probes were designed initially for VTVMs which do maintain the same input impedance .
That said, I have even seen ones designed for use with AVO Model 8s.

The most interesting ones came complete with their own display, in the form of an "Electrostatic voltmeter".
beanflying:

--- Quote from: vk6zgo on April 23, 2019, 08:24:37 am ---Not  that it matters with commercial probes, because you always use the highest  range.

Many older probes were designed initially for VTVMs which do maintain the same input impedance .
That said, I have even seen ones designed for use with AVO Model 8s.

The most interesting ones came complete with their own display, in the form of an "Electrostatic voltmeter".

--- End quote ---

Interesting Pintek is still making a version of something similar http://www.pintek.com.tw/product_detail/landersound/index.php?Product_SN=19263&Company_SN=6002&Product_Site_Classify_SN=17071

Making something similar with a modded handle wouldn't take a lot mainly a case of sourcing a good quality movement. The Digital one given cheap DMM's I wonder about even more  :-//



vk6zgo:

--- Quote from: beanflying on April 23, 2019, 08:28:58 am ---
--- Quote from: vk6zgo on April 23, 2019, 08:24:37 am ---Not  that it matters with commercial probes, because you always use the highest  range.

Many older probes were designed initially for VTVMs which do maintain the same input impedance .
That said, I have even seen ones designed for use with AVO Model 8s.

The most interesting ones came complete with their own display, in the form of an "Electrostatic voltmeter".

--- End quote ---

Interesting Pintek is still making a version of something similar http://www.pintek.com.tw/product_detail/landersound/index.php?Product_SN=19263&Company_SN=6002&Product_Site_Classify_SN=17071

Making something similar with a modded handle wouldn't take a lot mainly a case of sourcing a good quality movement. The Digital one given cheap DMM's I wonder about even more  :-//





--- End quote ---

I have used one like in the first picture, but the Electrostatic ones were different again.

The display unit was remote at the end of an insulated lead like the DMM/VTVM with a normal one, but the electrostatic meter had a light source & optical system which projected the meter position onto a wide curved display screen on the front of the unit.
The cases of these units were painted flat silver, & had a strange curved "streamlined "shape,which, together with the probes, gave them very much a 1960s "Doctor Who" appearance.

I don't remember seeing them used, & now, I wish I had taken a photo of them, just for their "weirdness coefficient"! ;D
beanflying:
There is some odd ones out there.  :) Having a trawl for Capacitive and higher frequency dividers and came across this (Page 15) http://hparchive.com/Catalogs_Specialized/HP-Catalog-195x-UHF-Equipment.pdf

My 427A Manual also mentions the 11039A (was 452A) Capacitive Divider but I cant seem to find it in any details on it. HP also seem to have had a preference for dropping a 1MOhm resistor across the probe to get to their 1000:1 for their resistive ones which would help with the meter variations.
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