Re: Wanted: HP 3458a DVM in non-working condition
The most challenging aspect of the analog design for me was the overvoltage and? ESD protection of the Ohms converter current source using a minimum of CHEAP off-the-shelf parts.? I spent many months on this design which I will go through in detail in my DMM video tutorial.? ?Some of the design is quite clever in my opinion - (could it be anything else - LOL)
I remember admiring the Ohms current source protection in the 34401A, looks like it derives directly from the 3468A design.
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Re: HP Agilent 34330a current shunt
Just from the photos those cheap ebay shunts are poor quality.
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Re: Wanted: HP 3458a DVM in non-working condition
Dennis,
The most challenging aspect of the analog design for me was the overvoltage and? ESD protection of the Ohms converter current source using a minimum of CHEAP off-the-shelf parts.? I spent many months on this design which I will go through in detail in my DMM video tutorial.? ?Some of the design is quite clever in my opinion - (could it be anything else - LOL)
With no cost constraints and modern components, I would have chosen much better op-amps, voltage reference, and ohm reference resistor.? ?I think you are asking how one might soup up the 3468A.? This can be done and I will address this in my video series.? There are certain errors that are introduced by the input bias currents and offset voltages of the op-amps used in the Ohms and? DC circuits.? By proper analysis of the circuits, the important parameters can be identified to tell one how to select a given op-amp for the function desired to minimize drift over time and temperature.? You can only carry this so far of course because the input hybrid will eventually become the limiting factor.? ?Now of course if you wanted to get crazy about this, you could render the drift of the fineline resistors in the input hybrid U102 as a moot point by surrounding it in a temperature controlled environment but that is getting foolish since the A/D tops out at 300,000 counts.
The single most important imporvements that could be made is using a 40K? Vishay S102 series resistor for the Ohms reference and an LTZ1000 for the DC reference.
The design philosophy for the 3478A was different than the 3468A.? The 3468A was intented to be used as a portable bench instrument that could be taken out in the field with an Hp41C calculator for data acquition.? The 3478A was intended to be used as a system meter hence the HP-IB interface.? Plus as a system meter there needs to be an in-guard and out-guard to isolate the analog and digital sections when used as a system meter in a rack of other instruments.? This greatly stepped up the power requirements which made the battery backup option a non-starter.? Besides that, the 78 was NEVER intended to have battery power.? It was from the start conceived to be a rack instrument.
To further differentiate and justify the price difference between the 68 and 78,? marketing insisted (I objected and was over ruled) that the 78 have one more lower range on DC and Ohms.? You will notice that the 78 has a 30mV and 30 ohm range that the 68 does not.? ?All the circuitry and hooks are in the 3468A to have those functions but the firmware will not turn them on.??
Unfortunately,? I have no way to give you to access those ranges on the 3468A.? That would require a firmware change and these is no spare memory in the Intel 8048 and external chips to hold the required code.? If there was space, we would have put some "back door" way of doing it for testing etc. but we could not.? You could "cheat" the instrument into providing those ranges but that would require external jumpers between Input hybrid pins and would require you to be inside the instrument to manually move the jumpers around.? Besides the display would not position the decimal point in the correct place if you did that so other than to play and have fun, it has no practical use.
On the lower DCV ranges, the input impedance is typically around 10^12 ohms or more.? There is always stray capacitance in parallel with that so as charge bleeds into the input and charges the stray capacitance, the instrument measures the voltage on the capacitance and that is the drift you see.? ?The leakage currents that charge these strays are from the? POSITIVE sources of voltage which are more dominant around the front end of the instrument.? You are more likely to find drift upward due to positive leakage currents rather than negative leakages.? ?
Remember? ? ? Q =? C V? ? ?so? ? ? ? ? ??i? =? dQ/dt? =? C? dVdt
? ? ? ? ?hence,? voltage drift:? ? ? ? dV/dt = i / C
If leakage current is? ?i = 1pA? and? C = 10 pF? ?then the drift is? ? dV/dt? =? ?1pA/10pF? =? 0.1v / second
Thanks for the kind words.? It is hard for me to believe that I was in HP Labs 41 years ago designing the 3468A.? In many ways it seems like yesterday.? ?I have vivid and fond memories of those days and the people I worked with.? The KEY project was a new approach taken by Hp to the design and manufacture,? Our team worked closely with all the support groups from the IC, PCB, marketing, industrial design, machine shop departments and the production floor.? ?I made many good friends from all the various departments.? This was not a case where the engineers in the lab were isolated and thru specs over the fence to the support groups and waited from them to return a proto back to us.? ?I and the other engineers had our own work benches and we each built and tested our own designs and interfaced our modules into a central prototype we kept in our area.? We had no "offices" with doors.? Our desks and work benches were all together where we could see and talk to each other without getting up.? Of course that lead to a lot of pranks for stress releif and camaraderie.? ? A close working relationship with the support groups helped the success of the project.? For example,? the PC shop worked closely with us in developing an new coating process for the motherboard PCB to eliminate teflon standoffs (many in the 3455A and 3456A) to insure high impedance at critical nodes with feed-thru components.? This was a big breakthrough that helped keep manufacturing costs low.? Had that aspect of the PCB manufacture not been successful, meeting the design goals would have failed.? ?There were many new innovations that required various departments to pull off successfully and not just from us design team engineers.
Hope that helps you with your questions.
George Hnatuik, PE
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Re: HP Agilent 34330a current shunt
There are low cost Chinese shunts available on ebay. For a few dollars more you can get an LED voltmeter/ammeter with a shunt. I haven't tried them.
Regards, John
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Steve - Home Sent: Friday, December 20, 2019 3:10 PM To: [email protected]Subject: Re: [HP-Agilent-Keysight-equipment] HP Agilent 34330a current shunt I got mine les than a year ago on the auction site, less than $30 and free shipping. New condition, too. If you¡¯re not in a rush it pays to watch for a while! Love it and although it doesn¡¯t get used often, it works for me. I rarely use it for more than 10 or so minutes at a time so no worries about overheating. Steve On Dec 20, 2019, at 11:52 AM, Alex <hpagilentgroup@...> wrote:
?I wanted to ask what is the opinion on the 34330A current shunt. Occasionally one needs to measure current somewhat above the 10Amps which is the maximum that my 973A/974A handheld DMMs allow. So I was wondering if this 30A external plugin shunt adapter would be a cost effective addition to keep on hand, of course considering that this would also require beefier connecting test leads that are current rated accordingly. But given the ebay price range for a 34330A being at $130-$300, I wonder if these numbers realistically make sense, not that I would even consider buying one just for occasional use at those prices anyhow. Since all of them have been listed for months now, and perhaps they are just the leftover overpriced bunch waiting for a desperate buyer, what would be a realistic lower price expectation for a working one in decent shape?
Or perhaps would other alternatives like a current probe adapter (34134A/34135A) be a better alternative? On the other hand I already have a FW-Bell GC-100D 200Amp AC/DC stand alone clamp-on "current gun" but it has a single range 3.5 digit readout up to 199.9, so measurements towards the lower end of that scale are not ideal, although still workable if need be. The gun also has two separate output jacks which I tried to use a couple of times but the output voltage never did make much sense in comparison to the actual measured current indicated on the display, which was correct. Maybe I was doing something wrong there, but the clamp by itself works fine when it gets used once in a while.
Of course yet another alternative that comes to mind would be to just buy a sturdy precision 0.01 or 0.001 ohm resistor at Mouser/Digikey and mount it inside a small metal enclosure with in/out jacks to use as a stand alone shunt, so it does not even need to stay attached directly or even near to the DMM.
I really don't have any very high precision needs, which are usually satisfied with either one of the multiple 4.5-digit 974A's on the bench, and certainly nothing beyond the capability of my "higher end" 3468A/3478A pair of not-calibrated for a long time DMMs. But still the idea of having a plug-n-play 30Amp quick expansion for the handheld DMM like the 34330A shunt when occasional needs arise still sounds interesting, specially when it is an HP product.
I am open to comments and suggestions. Thanks.
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Re: HP Agilent 34330a current shunt
I got mine les than a year ago on the auction site, less than $30 and free shipping. New condition, too. If you¡¯re not in a rush it pays to watch for a while!
Love it and although it doesn¡¯t get used often, it works for me. I rarely use it for more than 10 or so minutes at a time so no worries about overheating.
Steve
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On Dec 20, 2019, at 11:52 AM, Alex <hpagilentgroup@...> wrote:
?I wanted to ask what is the opinion on the 34330A current shunt. Occasionally one needs to measure current somewhat above the 10Amps which is the maximum that my 973A/974A handheld DMMs allow. So I was wondering if this 30A external plugin shunt adapter would be a cost effective addition to keep on hand, of course considering that this would also require beefier connecting test leads that are current rated accordingly. But given the ebay price range for a 34330A being at $130-$300, I wonder if these numbers realistically make sense, not that I would even consider buying one just for occasional use at those prices anyhow. Since all of them have been listed for months now, and perhaps they are just the leftover overpriced bunch waiting for a desperate buyer, what would be a realistic lower price expectation for a working one in decent shape?
Or perhaps would other alternatives like a current probe adapter (34134A/34135A) be a better alternative? On the other hand I already have a FW-Bell GC-100D 200Amp AC/DC stand alone clamp-on "current gun" but it has a single range 3.5 digit readout up to 199.9, so measurements towards the lower end of that scale are not ideal, although still workable if need be. The gun also has two separate output jacks which I tried to use a couple of times but the output voltage never did make much sense in comparison to the actual measured current indicated on the display, which was correct. Maybe I was doing something wrong there, but the clamp by itself works fine when it gets used once in a while.
Of course yet another alternative that comes to mind would be to just buy a sturdy precision 0.01 or 0.001 ohm resistor at Mouser/Digikey and mount it inside a small metal enclosure with in/out jacks to use as a stand alone shunt, so it does not even need to stay attached directly or even near to the DMM.
I really don't have any very high precision needs, which are usually satisfied with either one of the multiple 4.5-digit 974A's on the bench, and certainly nothing beyond the capability of my "higher end" 3468A/3478A pair of not-calibrated for a long time DMMs. But still the idea of having a plug-n-play 30Amp quick expansion for the handheld DMM like the 34330A shunt when occasional needs arise still sounds interesting, specially when it is an HP product.
I am open to comments and suggestions. Thanks.
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Re: HP Agilent 34330a current shunt
Here's an example found in one of my junk boxes of store bought 4 wire shunts that are probably available on ebay:
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Re: HP8753D Test 53 Sampler Magnitude and Phase Correction Constants fails
Hi all again, keeping the monologue alive :-)?
Last night I had help of a friend doing some more tests and measurements. We did several tests and measurements of the pulse generator and samplers. Most signals looked like the service manual pictures but up to 10dB lower. However we could add 19dB to the R sampler input before the phase lock was lost so we concluded that these parts worked fine. Like many other parts. But one thing bothered us and that was the bad S11 and S21 measurements without calibration. How about 9-17 dB amplification in just a cable? :-) So we played around with poking different values to the samplers, default is 46, not until -27 the S21 became negative.
So our conclusion is that I still had some garbage in my EEPROM that messes up the calibration tests.
So next steps would now be to copy my EEPROM with the programmer. Do an erase thru test 58 and then do each correction test in order and after each step take a new snapshot of the EEPROM to see what has changed. Also one mistake that I've previously done was to not do preset between each performed step. Also skipping to next step test after a failing one is not recommended.
So 13 EEPROM snapshots later I eventually today got to test 53 again, and it ran all the power measurements on both ports and since I once again was too eager so I forgot to measure the cable loss initially so when its was time for the finale of the test with the thru cable it failed. However the EEPROM was anyway filled with a large bunch of data I have not seen before and now my uncalibrated S11 and S21 looks reasonable. I have also verified that the sampler constant is 42, so my next step is to write 46 instead and rerun test 53 again, this time doing it exactly as instructed, the cable loss measurements and all. However I hope the test will be fine with not having APC-7 cables and can settle for APC-7 -> N-adapters and then N->SMA adapters, then good quality SMA cables. Also from EEPROM dumps I see that the sampler value is really a 16-bit value just like the 8753E version service guide says. And this value is not cleared by the EEPROM erase test.
So lessons learned on how to restore lost EEPROM data, besides learning a lot more about the inner workings of the 8753 are:
1. Do a preset between every performed test.
2. Do not skip to the next test if one fails.
3. Read the test instructions and perform each test thoroughly.
4. Having a socketed EEPROM and a EEPROM programmer is essential. I'll post later details about the EEPROM layout.
Next update will be more than a week away due to travel and holidays.
Cheers,
Marcus
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HP 70210C Spectrum analyzer
I've decided that my HP 71210C analyzer is way more than I will ever need anymore so I've decided to sell it.
This is a 100Hz to 22GHz unit, works great passes all self tests and calibrations.
Consists of:
70004A color display and frame
70001A frame
70908A RF
70902A IF
70903A IF
70310A reference osc with ext power supply
70900A controller/source
all interconnecting cables included.
Also with the working unit go these extra modules I acquired. These modules may or may not work without calibration or some repairs:
70004A color display and frame
70205A display and frame
70004A color display module only
70902A
70310A
70900A
70900B
70907B
70902A
And some original manuals
$1,500 takes it all, I won't ship, pickup only southeast PA north of Philly.
Contact me off list for any questions or pictures of the unit.
Chuck
www.myvintagetv.com
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Re: HP Agilent 34330a current shunt
One thing to note about the 34330A is that it is only rated at 30 amps for 15 minutes. Another option is to buy an industrial panel meter shunt and put it in a box. In europe 60mV is a standard for panel meters so a 60A one will give the same 1mV/A and addtional capacity. Nort American ones tend to be 50mV so go for a 50A one. About 1/3 the cost too. ?
A hall effect current clamp has even lower burden voltage and yu don't have to break into the circuit, but you will hae to pay four times as much to get similar accuracy s a shunt. If 1 to 4% is OK then the Pico technology TA018 is worth a look. mA to 60A for about the same price as the shunt.
If you want real dc accuracy get a Burster 1240-0.001 This will do 30A at 0.02% https://www.burster.com/en/products/p/detail/1240-1/
Robert G8RPI.
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Re: HP Agilent 34330a current shunt
On 12/20/19 11:05 AM, John Griessen wrote: Here's a quick 4 wire connected way to make it:
The nichrome heater wire can be salvaged from any kind of space heater, and will have a normal current of about 15 amps to get red hot. So, with big lugs for 8 gauge wire you can cripm together 4 of them to notn get it to go so hot with 30A you want to measure. Another way could be to use a less resistive wire like a steel coat hanger -- I have not tried that. Long ago on a production test line for a govt contractor we used kanthal wire for such resistors as part of the product instead of precise component shunts. Kanthal wire is not very available though.
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Re: HP Agilent 34330a current shunt
On 12/20/19 9:31 AM, Alex wrote: I was wondering if this 30A external plugin shunt adapter would be a cost effective addition to keep on hand, The way I look at high current measuring setups is I'm going to be doing some wiring anyway, so hooking in either a current transformer or shunt involves some clamping tight of connections, and breaking circuits to put those in place. So, if I'm already doing all that I can use a bit a nichrome wire. A bit of wire previously compared to a ref standard resistor at low amps. Here's a quick 4 wire connected way to make it: Split core current transformers for power meter use can be gotten off ebay for much less than $100, and would be the least intrusive 20 Hz and up method I can think of.
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Quantity Correction Re: [HP-Agilent-Keysight-equipment] FS: sets of NOS concentric control knobs
Brad Thompson via
Groups.Io wrote on 12/18/2019 7:48 PM:
Hello-- please note...
***Henceforth, if you have any questions regarding this or any other FS
offers that
I may make, please reply directly to my e-mail address. Thank you for
your consideration.***
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Brad Thompson via
Groups.Io wrote on 12/6/2019 10:29 A
Hello--
I'm offering FS sets of NOS concentric control knobs. These have
longitudinally-grooved
surfaces and black cursor markings which contrast nicely with the
aluminum knob material.
The top knob has a black insert.? Each knob gets secured to its control
shaft by two
.050-inch hex setscrews. A .jpg-format photo is available on
request.
Bottom knob: 0.625 inches in diameter, 0.56 inches high, 0.25 inch
through hole
Top knob: 0.425 inches in diameter, 0.56 inches high, 0.125 inch
blind hole.
(Please note that the knobs are made from aluminum, a conductive metal,
and hence will pose a shock hazard
if
you're accustomed to the bad practice
of floating the
ungrounded chassis of an instrument.)
Each set comprises FOUR top/bottom pairs and as a bonus while
the supply lasts, four skirted
plastic
knobs with 0.125-inch
brass-insert blind hole and one
0.050-inch setscrew.
I'm asking $10.00 per package? (four two-piece knobsets plus bonus
knobs), which includes
USPS first-class mail to U.S.
locations.
Questions welcomed, PayPal honored.
Thanks, and 73--
Brad? AA1IP
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Re: HP Agilent 34330a current shunt
Hi,
I have a 34330A, and I do not regret this purchase. At Keysight, it's $ 132
CAD or $ 101 US. I bought this product because it was specially designed for
voltmeters, including a standard plug, easy to use and of a size suitable
for these instruments. I bought cheaper from Digikey other shunt, but for
use with the oscilloscope mainly. Just like you I hesitated with making the
purchase mainly because of the price, but today I am happy to have bought
it.
Yves
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-----Message d'origine----- De?: [email protected]< [email protected]> De la part de Alex ·¡²Ô±¹´Ç²â¨¦?: 20 d¨¦cembre 2019 10:31 ??: [email protected]Objet?: [HP-Agilent-Keysight-equipment] HP Agilent 34330a current shunt I wanted to ask what is the opinion on the 34330A current shunt. Occasionally one needs to measure current somewhat above the 10Amps which is the maximum that my 973A/974A handheld DMMs allow. So I was wondering if this 30A external plugin shunt adapter would be a cost effective addition to keep on hand, of course considering that this would also require beefier connecting test leads that are current rated accordingly. But given the ebay price range for a 34330A being at $130-$300, I wonder if these numbers realistically make sense, not that I would even consider buying one just for occasional use at those prices anyhow. Since all of them have been listed for months now, and perhaps they are just the leftover overpriced bunch waiting for a desperate buyer, what would be a realistic lower price expectation for a working one in decent shape? Or perhaps would other alternatives like a current probe adapter (34134A/34135A) be a better alternative? On the other hand I already have a FW-Bell GC-100D 200Amp AC/DC stand alone clamp-on "current gun" but it has a single range 3.5 digit readout up to 199.9, so measurements towards the lower end of that scale are not ideal, although still workable if need be. The gun also has two separate output jacks which I tried to use a couple of times but the output voltage never did make much sense in comparison to the actual measured current indicated on the display, which was correct. Maybe I was doing something wrong there, but the clamp by itself works fine when it gets used once in a while. Of course yet another alternative that comes to mind would be to just buy a sturdy precision 0.01 or 0.001 ohm resistor at Mouser/Digikey and mount it inside a small metal enclosure with in/out jacks to use as a stand alone shunt, so it does not even need to stay attached directly or even near to the DMM. I really don't have any very high precision needs, which are usually satisfied with either one of the multiple 4.5-digit 974A's on the bench, and certainly nothing beyond the capability of my "higher end" 3468A/3478A pair of not-calibrated for a long time DMMs. But still the idea of having a plug-n-play 30Amp quick expansion for the handheld DMM like the 34330A shunt when occasional needs arise still sounds interesting, specially when it is an HP product. I am open to comments and suggestions. Thanks.
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HP Agilent 34330a current shunt
I wanted to ask what is the opinion on the 34330A current shunt. Occasionally one needs to measure current somewhat above the 10Amps which is the maximum that my 973A/974A handheld DMMs allow. So I was wondering if this 30A external plugin shunt adapter would be a cost effective addition to keep on hand, of course considering that this would also require beefier connecting test leads that are current rated accordingly. But given the ebay price range for a 34330A being at $130-$300, I wonder if these numbers realistically make sense, not that I would even consider buying one just for occasional use at those prices anyhow. Since all of them have been listed for months now, and perhaps they are just the leftover overpriced bunch waiting for a desperate buyer, what would be a realistic lower price expectation for a working one in decent shape?
Or perhaps would other alternatives like a current probe adapter (34134A/34135A) be a better alternative? On the other hand I already have a FW-Bell GC-100D 200Amp AC/DC stand alone clamp-on "current gun" but it has a single range 3.5 digit readout up to 199.9, so measurements towards the lower end of that scale are not ideal, although still workable if need be. The gun also has two separate output jacks which I tried to use a couple of times but the output voltage never did make much sense in comparison to the actual measured current indicated on the display, which was correct. Maybe I was doing something wrong there, but the clamp by itself works fine when it gets used once in a while.
Of course yet another alternative that comes to mind would be to just buy a sturdy precision 0.01 or 0.001 ohm resistor at Mouser/Digikey and mount it inside a small metal enclosure with in/out jacks to use as a stand alone shunt, so it does not even need to stay attached directly or even near to the DMM.
I really don't have any very high precision needs, which are usually satisfied with either one of the multiple 4.5-digit 974A's on the bench, and certainly nothing beyond the capability of my "higher end" 3468A/3478A pair of not-calibrated for a long time DMMs. But still the idea of having a plug-n-play 30Amp quick expansion for the handheld DMM like the 34330A shunt when occasional needs arise still sounds interesting, specially when it is an HP product.
I am open to comments and suggestions. Thanks.
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Re: HP8753 VNA step attenuator model and replacement
For the manual?: ? Yves ? ? Here is the description: ? The 33321 series of attenuators are all very similar. ?The differences are in the frequency range, programming voltage, input/output connectors and the programming voltage connector. Internally they are 4 sections (10dB, 20dB, 20dB, 20dB). ?There exists an E-manuel that describes the options, specs, etc. ?I will post it when I track it down. ?Do check the Agilent, Keysight websites with a search for ¡°33321 manual¡±.
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Re: Wanted: HP 3458a DVM in non-working condition
George,
Thank you for the very interesting and insightful answer. I feel very honored to have an analog designer of my most prized multimeter directly respond to me.
I do have a couple questions about the 3468A if I may.
First, what aspect did you find most challenging to design and implement?
Second, if the budgetary requirements were lifted, what would you have done differently?
Third, if you had access to modern analog components (except for mixed signal parts like ADCs/DACs), what would you change?
Fourth, why did future models, like the 3478A, drop the battery power?
Finally, when open circuit in VDC mode on the 0.3V and 3V ranges, why does the voltage drift up and not down? I know 10^10 ohm input impedance makes open circuit drift inevitable, but it¡¯s interesting that it always drifts up on my meter. I am still impressed that a 5.5 digit battery powered reasonably portable meter exists at all. To my knowledge, no more precise portable DMM has been sold since (save for maybe one 6.5 digit Metrahit model, but its long term specs are about on par with the 3468A). I love being able to move it (and the 3466A) around my cluttered bench without having to worry about power cords and being able to charge them indefinitely when not using them. Again, thank you for all of the insight! Sincerely, Dennis Chertkovsky
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On Dec 19, 2019, at 8:06 PM, " ghnatiuk@..." < ghnatiuk@...> wrote: Dennis,
At the time the 3468A was being developed, the LCD technology at Hp was in codevelopment with cooperation between the Loveland Instrument group and the Corvalis Calculator group.? There were no backlit LCDs at the time to be designed into the instrument.? This was a new technology.? We actually started with the LCD display from the 41C calculator in the engineering prototypes of the 3468A until the larger LDC eventually used in the 3468/78/57/88 was developed and prepared for manufacturing.? The 3468/78 and the LCDs were in development from 1978 -1981.? The project "KEY" for the 3468A was the first electronic calibration DMM for Hp.? ?The project began and started to ramp up after July 1978 and I joined as chief analog designer (5) for the front end signal conditioning in October 1978.? By February 1979 we had our full design team in place:
(1)? Project manager
(2)? Firmware/digital?
(3)? A/D and digital interface?
(4)? Hybrid switches and? DC? front end and attenuator
(5)? Ohms / AC / DC interface / Motherboard PCB and Input hybrid layout with fineline resistor networks
(6)? Power supply / battery backup / LCD? display
(7)? Mechanical and industrial design
Most of us were new engineers fresh out of university except for 3 members of the team (1),(2),(7)
The mission was to design a 5-1/2 digit DMM with full electronic CAL using less than 100 parts and for a parts cost of $100 or less.? We got close to the goal but had to increase the parts count because to meet safety requirements and that required for the necessary protection circuits for ESD and potential customer abuse.? That took more parts than first anticipated.
George Hnatiuk? ? Dec 19, 2019
Have a happy holiday
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Re: Wanted: HP 3458a DVM in non-working condition
Dennis,
At the time the 3468A was being developed, the LCD technology at Hp was in codevelopment with cooperation between the Loveland Instrument group and the Corvalis Calculator group.? There were no backlit LCDs at the time to be designed into the instrument.? This was a new technology.? We actually started with the LCD display from the 41C calculator in the engineering prototypes of the 3468A until the larger LDC eventually used in the 3468/78/57/88 was developed and prepared for manufacturing.? The 3468/78 and the LCDs were in development from 1978 -1981.? The project "KEY" for the 3468A was the first electronic calibration DMM for Hp.? ?The project began and started to ramp up after July 1978 and I joined as chief analog designer (5) for the front end signal conditioning in October 1978.? By February 1979 we had our full design team in place:
(1)? Project manager
(2)? Firmware/digital?
(3)? A/D and digital interface?
(4)? Hybrid switches and? DC? front end and attenuator
(5)? Ohms / AC / DC interface / Motherboard PCB and Input hybrid layout with fineline resistor networks
(6)? Power supply / battery backup / LCD? display
(7)? Mechanical and industrial design
Most of us were new engineers fresh out of university except for 3 members of the team (1),(2),(7)
The mission was to design a 5-1/2 digit DMM with full electronic CAL using less than 100 parts and for a parts cost of $100 or less.? We got close to the goal but had to increase the parts count because to meet safety requirements and that required for the necessary protection circuits for ESD and potential customer abuse.? That took more parts than first anticipated.
George Hnatiuk? ? Dec 19, 2019
Have a happy holiday
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Re: HP 8920A and 8920B Keypads Identical?
Hi,
?I can confirm that the 8920A and B keypads are the same. Why are you replacing the keypad? Is it just the rubbers or the PCB too?
The part number is 08920-40001
How much are you looking at for the replacement? I have a similar onne but the "softkeys" at the side of the screen and presets at top of panel have different markings. If this doesn't matter to you or they are OK on the existing one (you can cut the rubber up and just replace the faulty section). it might be an option.
Robert G8RPI.
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Re: HP8753 VNA step attenuator model and replacement
Here is the description: The 33321 series of attenuators are all very similar. ?The differences are in the frequency range, programming voltage, input/output connectors and the programming voltage connector. Internally they are 4 sections (10dB, 20dB, 20dB, 20dB). ?There exists an E-manuel that describes the options, specs, etc. ?I will post it when I track it down. ?Do check the Agilent, Keysight websites with a search for ¡°33321 manual¡±. Don Bitters
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Re: How difficult is it to find or source replacement cables for the HP 4195A?
Hello,
I have one too, and am limited to Spectral Analysis.
The test kits, and especially the impedance analyzer, is almost impossible to get. OK, I missed the one for 125USD at ppauctions...but in general, these are almost impossible to find.
With best regards
Tam HANNA
Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at
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On 2019. 12. 19. 0:27, Dave McGuire wrote: On 12/18/19 6:18 PM, ian.p.brown@... wrote:
I am considering purchasing a used HP 4195A network spectrum analyzer
that has both the display and measurement units but is missing the
cables to connect them. How difficult is it to source or find cables to
connect them? Is there anything unique about the cables? Any idea how
much replacement cables would cost? It's not tough at all. You'll need one cable with 50-pin AMP Champ
series connectors (what people who don't bother to learn call
"centronics" or "SCSI" connectors), and if memory serves a DE9 cable, I
don't recall the gender but that should be easy to figure out.
50-pin AMP Champ cables have been commonly used in telephony for
decades, and are known there as "25-pair" cables. They are easy to find
and not terribly expensive; I think I paid about $15 for a two-foot one,
new, on eBay.
The DE9 cables are commonly available via eBay or Amazon, cheap.
If you end up pulling the trigger on it, I can help you with the
specifics when the time comes. I can tell you that I very much love the
4195A, it's a fine and very capable instrument.
-Dave
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