[ARC5] BC-348-Q Capacitor Questions

Tue Aug 24 00:15:35 EDT 2010

Yes, I do realize that ;0)

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: Tuesday, August 24, 2010 12:13 AM
Subject: Re: [ARC5] BC-348-Q Capacitor Questions


> They are entirely different.
> The HP 410 is a DC VTVM.
>
> The HP 428 is a fluxgate clip on DC & low frequency current probe.
>
> Best,
>
> -John
>
> ==============
>
>
>
>
>> 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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