Red plate KT88 - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th September 2012, 12:58 AM   #31
20to20 is offline 20to20  United States
diyAudio Member
 
20to20's Avatar
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Meter lead resistance won't have any impact for a voltage measurement across a sense resistor wired in to the cathode circuit :-)
Ya, the voltage measurement is not where the error starts. It's in determining the resistance value. If you check the resistor and it "reads" 1R, the meter leads are adding anything from .1 -.3 R which means the real resistor value is .7 -.9. My Fluke 77 will read .1 -.2 R in the autoranging mode between leads, on a good day. So .05/.8 = .0625 instead of .05. Whereas .5/9.8 = .051.

Last edited by 20to20; 13th September 2012 at 01:16 AM.
  Reply With Quote
Old 13th September 2012, 02:15 AM   #32
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Yes, trying to read a 1 ohm resistor with a typical fluke is asking for question marks on accuracy. Even using a DC supply and a current meter and a voltage meter still needs meters with good resolution and accuracy. I take a backward step and use a new modern commercial resistor, with the view that anything from 1% to 5% tolerance is likely to give me more confidence than trying to make a 'measurement' of the resistors resistance value.
  Reply With Quote
Old 13th September 2012, 12:47 PM   #33
20to20 is offline 20to20  United States
diyAudio Member
 
20to20's Avatar
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Originally Posted by trobbins View Post
Yes, trying to read a 1 ohm resistor with a typical fluke is asking for question marks on accuracy.

Even using a DC supply and a current meter and a voltage meter still needs meters with good resolution and accuracy.
I think having the Fluke read my meter lead resistance is added accuracy. It's just that there is no "0" adjust possible as in many analog meters. I have three sets of meter leads from different quality meters I've purchased and they all have different resistances.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Genalex KT88 Plate Dissipation Question Loren42 Tubes / Valves 7 28th April 2011 10:05 AM
Red Plate,Tube runaway, glowing screen grids pforeman Tubes / Valves 18 22nd September 2009 01:54 PM
Why does red plate spell early death? Ty_Bower Tubes / Valves 19 28th September 2008 03:37 AM
Is Red Circuit's Guitar controller Really RED? Paswa Chip Amps 7 20th May 2008 04:48 AM
Heathkit W-5M Red Plate Issue Trout Tubes / Valves 7 28th May 2006 02:18 AM


New To Site? Need Help?

All times are GMT. The time now is 01:00 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2