Looking for specs for a vintage HP Current Amplifier Model 1111A

[Engineer]

Hi, everyone.
Can anyone point me in the direction of the specifications for Subject
instrument. I've just refurbished one that I rescued from the
dumpster, but I'm not sure over what frequency range it works - checks
out good at 60 Hz, but what about audio frequencies?
BTW, it consists of three pieces:
1. a magnetic split-toroidal probe, plus coax cable,
2. an electronics unit that drives a scope on the 50 mV/cm setting,
and
3. an old fashioned "wall-wart" p/s (before that term was in vogue!)
- all built like a brick outhouse, typical of HP from that era.
Cheers,
Roger
PS. I'd appreciate an email to "analogdino 'at' rogers 'dot' com" as I
don't get back here often! Many thanks.

 

[DaveM]

Hi, everyone.
Can anyone point me in the direction of the specifications for Subject
instrument. I've just refurbished one that I rescued from the
dumpster, but I'm not sure over what frequency range it works - checks
out good at 60 Hz, but what about audio frequencies?
BTW, it consists of three pieces:
1. a magnetic split-toroidal probe, plus coax cable,
2. an electronics unit that drives a scope on the 50 mV/cm setting,
and
3. an old fashioned "wall-wart" p/s (before that term was in vogue!)
- all built like a brick outhouse, typical of HP from that era.
Cheers,
Roger
PS. I'd appreciate an email to "analogdino 'at' rogers 'dot' com" as I
don't get back here often! Many thanks.

Nope, I ain't gonna reply to your email. You asked the question here, and you
should at least have the courtesy to look for your answer here.

OK, rant over.
The 1111A has a rise time of 18ns. Accuracy in X10 mode is +-3%, in X100 mode
is +-4%.
Max AC current above 700 Hz is 50A p-p. Below 700 Hz, the max current is
decreased by 1.4A/20Hz.
Output impedance is 50 ohms.
Noise is <100uA p-p, referenced to input.

I guess you could estimate the upper frequency limit by figuring the bandwidth
similarly to the way an oscilloscope's vertical bandwidth and risetime are
related:
Fmax(Mhz) = (0.35 / Tr(us))
Based upon that formula, the Fmax of the 1111A is
0.35/18000 = 194 KHz

Of course, that's just a guess... you'll have to use some experimentation to
determine its useful upper limit. But according to the risetime spec, it's
surely capable of the full range of audio frequencies.

HTH
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

 

[Engineer]

Nope, I ain't gonna reply to your email. You asked the question here, and you
should at least have the courtesy to look for your answer here.

OK, rant over.

Well, that's a relief... I only came back to see if my post went in!

The 1111A has a rise time of 18ns. Accuracy in X10 mode is +-3%, in X100 mode
is +-4%.
Max AC current above 700 Hz is 50A p-p. Below 700 Hz, the max current is
decreased by 1.4A/20Hz.
Output impedance is 50 ohms.
Noise is <100uA p-p, referenced to input.

I guess you could estimate the upper frequency limit by figuring the bandwidth
similarly to the way an oscilloscope's vertical bandwidth and risetime are
related:
Fmax(Mhz) = (0.35 / Tr(us))
Based upon that formula, the Fmax of the 1111A is
0.35/18000 = 194 KHz

Of course, that's just a guess... you'll have to use some experimentation to
determine its useful upper limit. But according to the risetime spec, it's
surely capable of the full range of audio frequencies.

HTH
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.- Hide quoted text -

- Show quoted text -

Dave, thanks for the info - now copied into my specs file. I'll run a
test using an audio power amplifier into a 4 ohm load up to a few KHz
and see what I get. Oh, and I'm glad you did not email me... I would
not like accepting such an extravagant accommodation that I could
never repay.
Cheers (still),
Roger

 

[DaveM]

Well, that's a relief... I only came back to see if my post went in!


Dave, thanks for the info - now copied into my specs file. I'll run a
test using an audio power amplifier into a 4 ohm load up to a few KHz
and see what I get. Oh, and I'm glad you did not email me... I would
not like accepting such an extravagant accommodation that I could
never repay.
Cheers (still),
Roger

Good luck with your testing. You could repay by posting the results of your
testing back here, so that if anyone else might be going through the same pains
as you are would have the benefits of your work.

Cheers!!!

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.