Re: HP 410C VTVM

[Chuck Harris]

Hi Paul,

Don't expect any great tolerance for over voltage or over current from
a 410C! There is no fuse to protect the current shunt from such abuse.

Over voltage on the DC range is fairly safe because there is a 1M
resistor at the DCV probe tip. It will keep fault current down.

It is usually safer to use some expendable shunt, and a voltmeter for
such measurements.

-Chuck

Paul Sanchez wrote:
> Thanks, Chuck. I'm planning to only use it for ma/tube current. I keep
> blowing up digitals with inadvertant
> probes.
> Do you know how "sensitive" these are to these inadvertant slips?
> Thanks again.
>
> "Chuck Harris" > wrote in message
> ...
>
>>The use of a 410C requires some care, particularily
>>on the AC range. The metal bodied AC probe contains a vacuum
>>tube diode that is sensitive up to 700 MHz. Further,
>>its case is at chassis ground.
>>
>>Ohms, and DC ma are read using the common and ohms/ma lead set.
>>Only DC is measured with the special DC probe.
>>
>>-Chuck
>>
>>Paul Sanchez wrote:
>>
>>>I got a nice looking, recently calibrated(21001) HP 410C VTVM.
>>>I've been spoiled too long with digital meters. Which probes do I use
>
> for
>
>>>measuring DC current?
>>>Also, unfortunately, it doesn't read any AC voltages beyond 300v(design
>>>limits).
>>>Thanks
>>>
>>>--
>>>No Tubes? You Lose!
>>>www.redironamps.com
>>>
>>>
>>
>
>

[Tom Bavis]

On Thu, 07 Aug 2003 16:04:59 GMT, "Paul Sanchez"
> wrote:

>I got a nice looking, recently calibrated(21001) HP 410C VTVM.
>I've been spoiled too long with digital meters. Which probes do I use for
>measuring DC current?
>Also, unfortunately, it doesn't read any AC voltages beyond 300v(design
>limits).
>Thanks

You don't have the AC capacitive divider then? Probably a rare item
these days. I used to measure the PEP output of 10 KW sideband
transmitters with one.

My 2 cents:
Best meter for measuring DC curent via shunt method is
the Simpson 260 "P" series A 260-7P is the one I use. I have 2 here at my
shop and have been using for 8 years or so. The P series has an overload
relay that kicks out a breaker on the front panel of the meter when you
accidentally short the probe. All you need to do is reset the breaker
button. I haven't changed a fuse in this meter ever! It takes two batteries
and I don't think I have ever had to change either of those either - in 8
years! It also has a higher DC & AC range than typical DVM's which is very
handy from time to time. The accuracy is not quite what a DVM might be but
again - for the current shunt breaker feature alone - in the few cases that
I have compared to a DVM it has been very close to the money and is
certainly accurate enough when you considder having to pull that little
plastic thing off the back of your Fluke again, to change the special sized
fuse in there - a pain in the ass. Get the 260 you won't regret it.
TS
"Paul Sanchez" > wrote in message
m...
> I got a nice looking, recently calibrated(21001) HP 410C VTVM.
> I've been spoiled too long with digital meters. Which probes do I use for
> measuring DC current?
> Also, unfortunately, it doesn't read any AC voltages beyond 300v(design
> limits).
> Thanks
>
> --
> No Tubes? You Lose!
> www.redironamps.com
>
>