"Standard" Probes - Page 1
Forum section: electronics / beginners

author: jcook793
author_rank: Newbie
timestamp: December 09, 2018, 08:40:20 pm
content: Hello!I've been an "ignorant tinkerer" in electronics for many years. I can do rudimentary things like test continuity and measure voltage, and I'm not afraid of soldering and desoldering through-hole parts. My main hobby is retrocomputing (mostly Commodore 8-bits) so it's generally enough to fix what needs fixing.Recently I acquired a decent-sized pile of test equipment that is way above my pay grade. I got some old Fluke meters, an HP 53310A domain analyzer, some pulse generators, sweep generators, and various other gray boxes that I barely understand. My goal is to pull out an item at a time, clean it up a little bit, replace any capacitors that might need replacing, read up on what it does and see if I can figure it out by using it. The bits that seem useful to me will find a spot on my bench, the rest will eventually get eBay'd (famous last words?).The big caveat is that none of these came with any probes. Most pieces have BNC connectors, though there are also several banana plugs. I'm going to buy some Probe Master leads and hopefully spend the least amount necessary to play with all this stuff. However my ignorance is really getting in the way here.For banana plugs, would the 8018S "Retractable Shroud Banana Plug" be the most universal option? For instance, on their site, they match the 8010S "Standard Banana Plug" for my Fluke 8012A, and the 8008S "Safety Banana Plug" for the Fluke 8050A. But it seems to me that the retractable version would work for either one, and should be useful for much of this other equipment as well.The BNC connectors are where I am the most lost, since I assume these are calling for scope probes and I really don't know anything about oscilloscopes other than roughly what they measure (voltage over time). Can anyone point me in the right direction there?Thanks!John

author: jeroen79
author_rank: Frequent Contributor
timestamp: December 09, 2018, 10:45:54 pm
content: I would go for simple unshrouded 4mm bananaplugs. (8010S)These will fit in both shrouded and unshrouded 4mm sockets.A retractable shroud would be an unnecessary complication IMO.Also get some banana to banana cables.For BNC gear you should get some oscilloscope probes with sufficient bandwidth (in MHz, Megaherz) and some BNC to BNC coax cables.Also get some adapters like BNC to banana, BNC to grabber or BNC splitters.

author: W0MPM
author_rank: Contributor
timestamp: December 09, 2018, 11:23:13 pm
content: The shroud is just a 'safety improvement' preventing accidental contact with the bare connections. Many - most - a lot of - vintage equipment doesn't come close to meeting modern standards. It relied heavily on operator knowledge and discretion. These Pomona are typical. You can see that even if the pins were protected the wire connections are right on the sides open to touch.https://www.pomonaelectronics.com/products/hardware/double-banana-plug-solderlessThat said it's hard to argue against the single shrouded 8018S and you are correct it should work in ANY banana jack. So go for itIt's not clear what you are asking with reference to the BNC. With reference to scopes, yes, most scopes and scope probes use BNC. But other test gear also uses BNC. If you have a scope and Probe Master lists a match then go for it also. You can't go wrong with the Probe Master probes.

author: xrunner
author_rank: Super Contributor
timestamp: December 09, 2018, 11:45:19 pm
content: Quote from: jcook793 on December 09, 2018, 08:40:20 pmYea the hp HP 53310A is a modulation domain analyzer, you won't have much use for that.It's nice to have it and the other items though in case you want to venture out.QuoteBNC is a major type connector for test equipment, but not everything uses a probe connected to a BNC. Many things are connected together with BNC to BNC cables. Might want to get some of them.

author: macboy
author_rank: Super Contributor
timestamp: December 10, 2018, 03:14:16 pm
content: BNC are very common in the electronics lab, but understand that not all things with BNC on them are necessarily inter-connectable.Typcially, a BNC connector and the cables have 50 Ohm characteristic impedance. Likewise, the inputs and outputs of the gear with BNCs will have 50 Ohm impedances. This impedance matching is necessary for signal fidelity. It avoids reflections, resonances, and other nasties.Most oscilloscopes are an exception. Although they use a BNC connector, they will have a high impedance input (1 Mohm in parallel with some few pF capacitance), and typical passive scope probes are designed to drive this impedance. There is in general no harm in connecting a 50 ohm source using a 50 Ohm cable to an oscilloscope input, but it will not be terminated (into 50 Ohms) by the oscilloscope. This means that the signal will be double the expected amplitude, and it will reflect back to the source. Most sources can handle this, but there can be exceptions. Some oscilloscopes have a switchable 50 Ohm termination, and you would usually choose to use it in this case, but must disable it when using passive probes which need the 1 MOhm input impedance. If the scope doesn't have this, then you can use either a feed-through terminator, or a BNC Tee with a terminator connected to one side.Banana leads are very handy to have, I'd recommend getting a set of various lengths and colors. Retractable shrouds are perfectly fine, compatible with both normal and safety type jacks. They can help prevent "oops" moments.You can get Banana to BNC adapters, and it doesn't hurt to have a couple around. Keep in mind that once you have a signal on flying wires, it is more susceptible to noise and won't work well at high frequencies (>> 1 MHz).Note that some BNC cables have 75 ohm impedance. Thesemaybe identifiable by a distinctly different looking BNC connector which has no which plastic dielectric surrounding the center pin, but also they may not, as many are built using 50 ohm connectors for some strange reason. Always look at the cable itself to determine impedance. Or measure it. You mentioned having at least one pulse generator, this can be used with an oscilloscope to make a simple TDR measurement. You also need a good BNC 50 ohm cable, a BNC Tee, and a homemade variable terminator. I built one of these from a small 100 ohm pot wired as a rheostat to a BNC plug (or jack). It's amazing how quickly you can learn about the relationship between signal integrity and impedance when playing with such a rig. I was also able to measure the impedance of a few mystery BNC leads I had acquired. It turns out they are 63 Ohm. Who would have thought?