I have a couple of pieces of equipment that could potentially be useful for electronics projects, and I’m interested in making them available to the lab. They are:
HP 8591E 1.8 GHz spectrum analyzer. This one is loaded with high-performance options, including the high-stability reference and narrow bandwidths, fast sweeps (FFT), and time-gated analysis, as well as the quasi-peak detector which can be used for EMC testing, although I think quasi-peak is overrated on a spectrum analyzer. It has the EMC personality routines pre-loaded. It’s been 3 or 4 years since it was cal’d, but was in spec at that time, and no tweaks were made. I’d expect it to be in spec now. This can be useful for all sorts of stuff if you know how to use it.
Tek 571 curve tracer. This is kind of a “mini” cuve tracer, compared with the Tek 576, 577, or 370 tracers. It’s fully computerized, has a variety of adapters built right in. It’s pretty nifty to have in the lab if you’re doing analog design, or sorting parts. It can be helpful to identify unmarked parts, to match diodes or transistors, or to characterize nonlinear elements in analog signal processing circuits. It’s a cute little machine: http://w140.com/tekwiki/wiki/571
These are not really specialized gear, but do require some knowledge to use. My question is, would anybody use either of these? Would they be a useful addition to the lab, or would they just take up shelf space? If they were part of a nice little dev bench, I’d be happy to bring them by, perhaps on a loaner basis for now.
This would get some use if we started doing Amateur radio homebrew sessions (something I’ve thought about doing). Might gather dust otherwise.
Yes, and like Daniel said, this needs to be locked up unless one has proper training. DC of any significant magnitude and RF over +10dBm or so will fry the 1st mixer and those aren’t cheap. A simple DC block barrel on the front will help prevent the former problem at the expense of low-end response, but the latter requires some care when looking at amplifiers.
I agree–I usually keep a 20dB attenuator on the input if the cover is off, except if a preamp, active probe, or non exposed probe (like E-field or H-field) is plugged in.
I have built LISN’s per MIL-STD-461 and RTCA DO-160. I still have a large spool of Litz wire to build the 50uH inductors. What current requirement do you have in mind? I have built LISN’s from 10 to 400 Amps per phase. I have also used the HP 8691E Spectrum Analyzer…very good unit if properly taken care of. - Richard Meyer
Usually I’m working in the low-handfuls of amps, in the 120V and 250V ranges, although I’ve had a few inklings to want to mess with 24V aircraft power.
This stuff knocks a whole half-day off of compliance testing worries, and it’s really easy to pre-scan with the right equipment. That’s basically what I’d want to use it for.
I don’t know if it’s actually possible to build one that works from 45Hz-66Hz, but that would be ideal, if somehow we got ahold of a powerline simulator at some point.
The 50uH LISN’s are used for MIL-STD-461 testing and their AC tests run from 50 Hz up to 800 Hz. RTCA DO-160 uses either a 5uH or a 50uH LISN over the same frequency range. The same LISN’s can be used for DC as well. Hand winding the inductors using expensive Litz wire is not a problem, a have a spool of Litz wire. Three phase testing requires another LISN for the Neutral line, 4 LISN’s in all. Sounds like a fun project.
I have parts to build 3 LISN’s with a current capacity of about 50 Amps each. Most of the commercial testing uses 50 uH LISN’s. For Lab and bench pre-qualification testing, that would fulfill the requirement pretty good even if an RTCA DO-160 tests requires a 5 uH LISN. The size of each aluminm chassis would measure 10" x 10" x 4". The only additional item you would need is an 8 foot table with a copper top, I have used copper screen material which works just as good as a temporary fixture. A good ground can be obtained by running a grounding wire from the building’s steel frame which is located above the ceiling tiles.
The Makerspace Electronics Lab has a history of throwing away alot of unused test equipment. Since only a few people know what a LISN is and how to use them, additional measures would have to be taken to prevent this equipment from disappearing on us.
Let me know if you want to go ahead with this project. Once the equipment is set up I could even teach a class about EMI testing, I’ve been doing it for years.
The 3 Line Impedance Stabilization Networks (LISN’s) are being built. I’ve already wound and tested the 50 uH inductors using Litz wire. They should handle AC or DC currents up to about 50 Amps. I’ve got the 3 aluminum boxes and just need to finish up drilling and installing all the parts. The LISN’s design is based on MIL-STD-461 which is the specification for EMI Testing.
For those that do not know what Litz wire is, it is an expensive twisted wire comprised of 525 strands of 36 gauge wire. As your frequency goes up the electrons tend to migrate to the outer circumference of the wire, known as the skin effect. So in order to keep the high frequency resistance at its lowest you need to use multiple strands of small gauge wire to increase the overall surface area of the final conductor. For the Litz wire used here, there are 75 strands of 36 gauge wire twisted together to form 1 of 7 other identical twisted strands. Then all 7 larger strands are twisted again together to form the final conductor with 525 small wires in it. This specific Litz wire is identified as 7x75/36. The final cable has the equivalent rating of 14 gauge wire, but with the high frequency capability.
Oh here is a great hint. If you need a copy of any Military Standard, try the website: http://everyspec.com/ and select the “Library” tab. All of the Standards are free. Find MIL-STD-461 if you want additional information how EMI Testing is performed. MIL-STD 462 goes into greater detail about EMI Testing. Enjoy
I don’t have an immediate need (haven’t been able to find it), but routinely create coils for RF work for which litz wire is great. Ideally, I would love to buy a full roll (couple of thousand feet) if you ever find a source.
When I said I had a large spool of Litz wire I meant that there is probably 100-200 feet on the spool left. From a hobbyist point of view, that is a large spool. I got my spool of Litz wire from my employer that was getting rid of it. I have never bought Litz wire myself, just used what I had for many years. So I cannot help you with a source. But I see that Cooner Wire at http://www.coonerwire.com has Litz wire. My Litz wire is Type 2, served. Type 2 means that it is a twisted multi-conductor wire, and served means it has a nylon insulation. If you want some, tell me how much but do not take it all. Leave some for others.
OK, this is going in a different direction from what I anticipated, but potentially useful to some of the engineer types. I certainly wouldn’t mind having access to some LISNs and a power line/fast transient simulator. However, I question if there is enough demand for a precompliance station to justify allocating space and security resources.
I thought that people might like a small RF setup for playing with simple RF circuits. A 1.8 GHz range is still plenty useful for lots of stuff. I realize an analyzer that gets up to the multi-GHz range would be useful for much of today’s standard radios, but I don’t anticipate seeing much development activity at those frequencies; I would expect a higher frequency analyzer would get used as a fancy LED to show the presence of the radio signal.
If there’s interest in setting up a precompliance station, I also have a minizap I could contribute, but we’d need to obtain some tips (or make them on the lathe). E-field and H-field apparatus would not be too hard to make from some wire and copper-clad board.
Either way, my intention would be to have a dedicated station with a goal of promoting some more advanced experimentation. I don’t see any of this stuff being useful without at least that level of commitment.
Hey, just speaking for myself here, but most of Makerspace is made up of really 'spensive stuff that people couldn’t afford on their own… a lot of professional-level+ work gets done at the space.
I have a pretty well-stocked lab at home, and would like if the space had more advanced equipment that is available when I need it. Despite the fact that is is a very nice lab space that stays well maintained, it still isn’t a very advanced lab – just the basics for when you need to put your robot kit together, more or less.
I don’t know if it is actually feasible, but my desire would be for a more advanced lab for those of us who could really get infrequent but good use out of stuff like that.
We are having issues keeping the 80% users in tools and supplies. I would love to have an advanced lab but infrequent use of expensive tools is kinda of a non-starter. I do hope for the future though! We are building up!
