The internal circuitry of the HP410C and the USM-116 AC probe looks
practically identical.
Also, the filament current of both the EA52 and the EA53 is the same, 300 mA.
It would most probably not be any problem to use the USM-116 in the HP410C,
there may possibly be a calibration issue on the 0.5 V range, but diode
voltmeters
are notoriously inaccurate on these ranges anyway.
73/
Karl-Arne
SM0AOM
----- Original Message -----
From: "David C. Hallam" <dhallam@rapidsys.com>
To: <craxd1@verizon.net>; <amps@contesting.com>
Sent: Tuesday, May 16, 2006 7:08 PM
Subject: Re: [Amps] VTVM Diodes
> Will,
>
> I am not too worried about the calibration. I am not doing anything that
> requires traceability to any standard. It is just for my own use. I can
> calibrate the meter myself close enough for my use.
>
> I just was trying to find out if there are any significant differences
> between the EA52 and EA53 that would kill the idea.
>
> David
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
> Behalf Of Will Matney
> Sent: Tuesday, May 16, 2006 12:33 PM
> To: amps@contesting.com
> Subject: Re: [Amps] VTVM Diodes
>
>
> David,
>
> The tube type differences could be the gain, or voltages, I'm not sure. The
> probes could possibly work, but those are the ones that used an acorn tube
> in the tip aren't they? Here's the biggest problem. If you change the
> tube(s), the meter will about sure be out of calibration. What happenes is
> that as the meter was used from when it was new, the tubes gradually got
> weaker while the meter was sent out once a year for calibration. Each time
> it was re-calibrated, it was to the weaker tube signals. When you put a new
> tube in that is 100%, it throws off the calibration. Solid state meters
> don't do this to that extent. The yearly calibration for solid state I don't
> think is needed. Maybe every three years, and that's if they're really used
> a lot. However, if a solid state is repaired, it needs to be checked for
> calibration then unless the part was out of the same batch as the original.
> Even then, there's a possibility it could be off because of the gain
> difference. The tube meters
> though really need the calibration over shorter spans over the tubes gain
> dropping over use. How much a new tube could throw it off, I'm not sure.
>
> What you could do is measure some standards if you have them, and write down
> the measured values. Really they don't have to be standards, just save the
> original parts you used to test back for the last test. Compare these
> measurements to the ones you get after you replace the tube, and adjust for
> them.
>
> Best,
>
> Will
>
> *********** REPLY SEPARATOR ***********
>
> On 5/15/06 at 4:36 PM David C. Hallam wrote:
>
> >I am trying to find an AC probe for my HP-410C. I have a probe from a USM
> >116 VTVM. The 410C uses an EA53 diode in the probe and the 116 uses an
> >EA52. From what I have found on the internet, these two tubes seem to be
> >similar, base connection, heater voltage, frequency range, etc. Does any
> >one know if I could use the probe from the USM 116 on the 410C?
> >
> >David
> >KC2JD
> >
> >
> >
> >
> >
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>
>
>
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