Telequipment D43 issues. - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

karesz* · 1st Nov 2015, 8:29 pm

Hallo Andy,
did you calculated please with the parallel input of -ie 10Mohm- your Multimeter?
In that case it needs better an 1,1MOhm_ Here is a DIY EHT/HV-probe & another, RF-compensated, script...
Karl

Diabolical Artificer · 3rd Nov 2015, 8:05 am

This is where it gets tricky for a relative novice like me, I know others struggle with the maths, especially when we havn't done any "serious" maths since school and don't use maths on a daily basis. I know that in comparison calculating resistors in parallel isn't a particularly advanced equation, but I struggled calculating this.

In the end I've got a sort of answer. With my meter having an input Z of 10meg or 10,000,000 ohms and the resistor - R1 I'm measuring across is 1 meg or 1,000,000 ohms, the actual resistance will be 0.990990991 meg or 990990991 ohms. Therefore with a voltage of 1000v across R1 the reading will be 1009.090909 volts, so a voltage reading 9v higher than actual.

I've read the articles you linked as well as others inc Keiths talk at Goldbourne and AFAIK I should be using a 1.1 meg resistor instead of a 1 meg as my measuring resistor, which is what you recommended Karl. Thanks for pointing that out.

Andy.

karesz* · 3rd Nov 2015, 11:29 am

Andy, you`r welcome,
If your HV resistors are all nominal 1% (or selected-measured as better), you can check it in a (good)knowed DC voltage-divider(ie paarwise), and you wish to have exacter dividing, put an additional serial ~91Kohm into the 10Mohm-line please - than you have exacter 100:1 ratio...
Karl

1st Nov 2015, 8:29 pm	#21
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: Telequipment D43 issues. Hallo Andy, did you calculated please with the parallel input of -ie 10Mohm- your Multimeter? In that case it needs better an 1,1MOhm_ Here is a DIY EHT/HV-probe & another, RF-compensated, script... Karl Last edited by karesz; 1st Nov 2015 at 8:38 pm.*

3rd Nov 2015, 8:05 am	#22
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: Telequipment D43 issues. This is where it gets tricky for a relative novice like me, I know others struggle with the maths, especially when we havn't done any "serious" maths since school and don't use maths on a daily basis. I know that in comparison calculating resistors in parallel isn't a particularly advanced equation, but I struggled calculating this. In the end I've got a sort of answer. With my meter having an input Z of 10meg or 10,000,000 ohms and the resistor - R1 I'm measuring across is 1 meg or 1,000,000 ohms, the actual resistance will be 0.990990991 meg or 990990991 ohms. Therefore with a voltage of 1000v across R1 the reading will be 1009.090909 volts, so a voltage reading 9v higher than actual. I've read the articles you linked as well as others inc Keiths talk at Goldbourne and AFAIK I should be using a 1.1 meg resistor instead of a 1 meg as my measuring resistor, which is what you recommended Karl. Thanks for pointing that out. Andy. __________________ Curiosity hasn't killed this cat...so far.

3rd Nov 2015, 11:29 am	#23
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: Telequipment D43 issues. Andy, you`r welcome, If your HV resistors are all nominal 1% (or selected-measured as better), you can check it in a (good)knowed DC voltage-divider(ie paarwise), and you wish to have exacter dividing, put an additional serial ~91Kohm into the 10Mohm-line please - than you have exacter 100:1 ratio... Karl