[FARC] Looking for a scope

[Mark Whitmore]

Jeff,

The safest way to connect the scope is with a special cord that I can 
provide.  This will have a
BNC connector on one end and a standard 120v AC connector on the other.  
The cord will have
a 1000 ohm resistor in series and a 50 ohm resistor to common giving a 
reduced voltage into
the scope of 20 to 1.  The peak voltage will be +/- 120 * 1.4 /20 = +/- 
8.4 volts.

Let me know if you want to go with this arrangement.

Mark
On 5/31/2016 10:07 PM, Jeff Fishman wrote:
> Mark,
> My friend actually lives in Hagerstown, so the RFI wouldn't be a factor for
> me! He became aware of the "wave" issue when an electric clock began gaining
> about two minutes a day. Modern inverters produce a much "closer to sine"
> wave but still not perfect. Will we need a special probe to measure line AC?
> Jeff
>
> -----Original Message-----
> From: FARC [mailto:farc-bounces at mailman.qth.net] On Behalf Of Mark Whitmore
> Sent: Tuesday, May 31, 2016 4:18 PM
> To: Frederick, Maryland ARC
> Subject: Re: [FARC] Looking for a scope
>
> Jeff,
>
> I have a Tektronics 465 that you are welcome to borrow.  I would also like
> to know what the inverter output looks like.  I am pretty sure it is NOT
> going to be a sine wave.
> The ones I have seen are called
> "modified sine wave" and have about 33% third harmonic content.  It looks
> like a central rectangle with a shorter rectangle on each side followed by
> the inverse (negative) of this. There are essentially six chunks of voltage
> with an RMS value of 120.  Don't think they bother to shape the edges since
> this would result in more dissipation in the transistors.  I would also be
> willing to bet that there are no requirements to limit electromagnetic
> radiation from either the solar array or the house
> wiring.   Have you turned on your radio
> since the neighbor went solar?
>
> Mark
>
> On 5/31/2016 11:19 AM, Jeff Fishman wrote:
>> Does anyone have an oscilloscope I can borrow for a few days? A friend of
>> mine just had a solar system installed at his home, and I'd like to see
> how
>> clean the AC wave really is before I take the leap.
>>
>>    
>>
>> Thanks.
>>
>>    
>>
>> Jeff KB3FIO
>>
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