[ARC5] BC-348-Q Capacitor Questions

[Henry Mei'l's]

Thanks John.

I just downloaded the HP 428 manual
I have an HP 410 -- not quite the same thing.

I'll see if  I can get hold of an HP 428 w/probe on the DK national used 
gear site.
My mails to your jfor at quik.com usually bounce - lets see what happens on 
this one.

Henry

----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Discussion of AN/ARC-5 military radio equipment." 
<arc5 at mailman.qth.net>
Sent: Monday, August 23, 2010 7:19 PM
Subject: Re: [ARC5] BC-348-Q Capacitor Questions


> >
>> On Aug 23, 2010, at 2:08 AM, Henry Mei'l's wrote:
>>
>>> Hello Dennis
>>>
>>> How does this work?I don't have an HP 428 but is there some way I
>>> can rig up
>>> something using standard VTVMs/VOMs &/or scopes to do the same thing?
>>>
>>> ----- Original Message -----
>>> From: "Dennis Monticelli" <dennis.monticelli at gmail.com>...
>>>> I find that it is easier and less invasive to use an old HP 428
>>>> clip-on
>>>> current meter to check caps.
>>
>> Basically, here is how the HP clip-on milliammeter works:
>>
>> The clip on probe contains a magnetic core that is placed over the
>> wire being tested.  The core is operated at a certain level of
>> magnetic flux by the instrument.  The DC current in the wire under
>> test, changes the flux in the core.  This change is detected by the
>> instrument and there is a corresponding reduction of the flux in the
>> core to return it to the original balanced state.
>
> It's called a flux-gate sensor.
>
>> So, the important parts of the system are:
>>
>> A unique clip-on core
>> A source of magnetism in the core that is monitored by the instrument
>> A feedback system to reduce the magnetism to restore the original flux
>> level
>> A metering system to display the detected current.
>>
>> Note: if you buy one of these HP meters without the clip-on probe, you
>> have a useless piece of equipment.
>>
>> There are clip-on probes meant for use with oscilloscopes that detect
>> AC currents in a wire, and may well be some that detect DC currents.
>> Tektronix, naturally, had/has such AC detecting probes. The one I know
>> of is quite old now, and had a little power supply and amplifier as
>> part of the setup.  It's frequency response was modest, but I think it
>> worked at line current and up to perhaps some couple of hundred kc.
>
> Tek had the 6021 & 6022 that worked with either a passive termination or
> the 134 amp, which went to a lower frequency, but not to DC.
>
> Tek also made some DC current probes, like the 6032. The current unit uses
> a similar technology with a TM500 amplifier module. These units go from DC
> to 50+ MHz.
>
>> I have a couple of devices that are called "Hall Effect sensors".
>> These things are based on relatively new creations of modern physics
>> that I don't understand, but I think they detect current in a wire
>> that is passing through the opening in the thing.  Search via Google
>> for "hall effect sensors" and you'll get lots to read. Apparently, you
>> can buy them at Digi-Key.  This seems to be a promising avenue to
>> explore.
>
> They are a small, gapped core with a Hall Sensor in the gap.
>
>
> est,
>
> -John
>
> =============
>>
>>
>> Roy
>>
>> Roy Morgan
>> k1lky at earthlink.net
>> K1LKY Since 1958 - Keep 'em Glowing!
>>
>>
>>
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