Bottlehead Forum

Bottlehead Kits => BeePre => Topic started by: rockpassion on February 13, 2013, 03:03:46 PM

Title: Question on Resistor value
Post by: rockpassion on February 13, 2013, 03:03:46 PM

I received my BeePre today, yeah!  Checking all my parts I have found one of the resistors value when measured with my DVM that it is different than the color code on the resistor.  The resistor in question is the first one shown on the parts list under the Filament regulator Bag heading.  It is shown as a 0.27 ohm resistor (black, red, violet, silver, brown).  However, when I measure it, it shows a .7 ohm resistance for both resistors.   

Will this still work or do I need a couple of new resistors.

Thanks

Richard

Title: Re: Question on Resistor value
Post by: Paul Joppa on February 13, 2013, 03:21:56 PM

What does your meter read when the probes are shorted to each other? 0.43 ohms, maybe? :^)

Title: Re: Question on Resistor value
Post by: rockpassion on February 13, 2013, 05:39:52 PM

Thanks Paul, my DMM measures .2 ohms when shorted. 

Title: Re: Question on Resistor value
Post by: Grainger49 on February 14, 2013, 02:05:19 AM

A DMM is at its worst reading low resistances, those under one ohm.  There is a costly industrial instrument made by Biddle (manufacturer of the Megger)  that measures low resistances.  I can't for the life of me remember the name right now.  I have used it to measure DC motor winding resistances down to 4 or 5 decimal places. 

Edit: Biddle makes a Ductor for low resistance readings.

Title: Re: Question on Resistor value
Post by: rockpassion on February 14, 2013, 02:10:46 PM

Well Paul Joppa was right, imagine that!!!  I first shorted just the DMM probes and my reading was 0.2 ohms.  But, I was using a pair of leads with alligator clips so I tried shorting these leads.  And low and behold it was 0.4 ohms.  So when I subtract the 0.4 ohms from the 0.7 ohms I get 0.30 ohms which is close enough to the 0.27 ohms called for.  Didn't realize the leads would slightly increase the resistance readings.

Thanks again Paul.

Richard

Title: Re: Question on Resistor value
Post by: Jim R. on February 15, 2013, 06:13:01 AM

Grainger,

It's called the Lohmeter.

-- Jim

Title: Re: Question on Resistor value
Post by: Grainger49 on February 15, 2013, 08:55:08 AM

Jim,

You are the one person here that I thought might know.  If it were an aircraft part Paul Joppa would know.

Title: Re: Question on Resistor value
Post by: Jim R. on February 15, 2013, 09:34:06 AM

And who knew that the father of that cute little girl in 3rd grade would have a company that made equipment that would part of my daily work later on in life?  Meggers, Lohmeters, hi-potters and all kinds of other high-voltage, high-current test equipment.

-- Jim