[Milsurplus] [ARC5] Smart People: Multi-Set Current Corn-fusion

[Jim Whartenby]

DaveIf you o'scope the power supply, is there any ripple?  If so then possibly the error in current that you see is the result of vector addition since it is not pure DC.Just a thought,Jim

      From: Mike Morrow <kk5f at earthlink.net>
 To: 'ARC-5' <arc5 at mailman.qth.net>; milsurplus at mailman.qth.net 
 Sent: Sunday, December 3, 2017 11:26 AM
 Subject: Re: [Milsurplus] [ARC5] Smart People: Multi-Set Current Corn-fusion
   
Dave wrote: 

> OK… with the antenna disconnected and all audio output at minimum:
>
> All off is now 12 mA. 
>
> Set 1: 28 mA
> Set 2: 33 mA
> Set 3: 35 mA
>
> All on: 78 mA
>
> Still a deficit of 18 mA.

Look at it this way to more accurately estimate the expected three-set total without the error of counting the screen voltage divider effects two too many times:

Common screen divider current, all three sets off = 12 mA

Current drawn by 46115 only, minus common screen divider current = 16 mA
Current drawn by 46116 only, minus common screen divider current = 21 mA
Current drawn by 46117 only, minus common screen divider current = 23 mA

Three-set current, not including common screen divider current = 60 mA
Three-set current, including common screen divider current = 72 mA

Your measured total of 78 mA for all sets operating is close to the more precise estimation above.  If you just add the raw individual operating set current flows, you are including the total screen divider current flow three times in the total instead of once.

What you really nedd to do is disconnect HV from the two sets that are off when you measure the current for the set that is on.  Only then can you add the three individual values and expect to get what will be measured when all three sets are on.

Mike / KK5F
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