[ARC5] BC-348-Q Capacitor Questions

[J. Forster]

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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>>
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