What's going on with probe pins? - Page 1
Forum section: electronics / testgear

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 09:23:31 am
content: As most will be aware some oscilloscope probes come with a pin in the BNC connector part. This pin lets oscilloscopes that support this feature know the probe attenuation. What's unclear to me is what's supposed to mechanically happen with that pin when used with oscilloscopes which don't support this feature. The pin obviously won't set the attenuation, but it does seem to scratch the material surrounding the BNC connector in the absence of a probe sense ring. Especially new pins can be relatively sharp and leave small bit distinct marks in what's generally plastic. This seems to be true even in oscilloscopes which come with said probes. Is this supposed to happen?

author: Gyro
author_rank: Super Contributor
timestamp: August 20, 2019, 10:03:18 am
content: It looks as if that probe is specifically designed for use with Tek scopes. Interesting, I didn't know anybody but Tek made them.Was it a recent purchase? Good price? spec? (particularly capacitance matching range).Tek probes are well known for scratching up non tek scopes- They used to lock pretty much permanently with the BNC mounting nuts of HP1740s!P.S. Your best bet is probably to find some thin metal shim washers, slightly larger id than the BNC socket.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 20, 2019, 10:11:55 am
content: Oscilloscope probes are not meant to be interchangeable between any oscilloscope models or brands.The fact that most probes have BNC connector is just a happy habit in the oscilloscope's industry, and not a mandatory standard.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 10:26:33 am
content: Quote from: Gyro on August 20, 2019, 10:03:18 amI picked a random example. You can see the same happening with the probes supplied with the Keysight 2000X series so it's definitely not just a matter of using inappropriate probes.

author: tautech
author_rank: Super Contributor
timestamp: August 20, 2019, 11:19:36 am
content: Quote from: Mr. Scram on August 20, 2019, 09:23:31 amIt doesn't, period.In the channel input attenuation settings menu you must manually set the probe attenuation.If the scope is an old CRO then you need to do the maths in your head, ahla old style.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 11:26:56 am
content: Quote from: tautech on August 20, 2019, 11:19:36 amThanks for your answer but this question isn't about attenuation."Setting the attenuation obviously doesn't work, but the pins do seem to scratch the material surrounding the BNC connector. Especially new pins can be relatively sharp and leave small bit distinct marks. This seems to be true even in oscilloscopes which come with said probes. Is this supposed to happen?"

author: tautech
author_rank: Super Contributor
timestamp: August 20, 2019, 11:32:58 am
content: Quote from: Mr. Scram on August 20, 2019, 11:26:56 amWell normally the probe sense ring is gold plated metal so you'd want a good connection so that the auto attenuation setting is maintained therefore any material that isn't metal will suffer from contact with the pin.Old scopes always show some marks from auto sense pins.Use some 400 grit emery to blunten it some and call it a day.

author: Fungus
author_rank: Super Contributor
timestamp: August 20, 2019, 11:44:10 am
content: Quote from: Mr. Scram on August 20, 2019, 09:23:31 amSimple: It isn't.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 11:58:35 am
content: Quote from: tautech on August 20, 2019, 11:32:58 amIf there's a probe sensing ring it's not that complicated as those are intended to receive the pin. Less obvious is the intended mode of operation when these probes with pins are supplied with oscilloscopes without probe sensing rings. Marring is intended?

author: BillB
author_rank: Unknown
timestamp: August 20, 2019, 12:05:33 pm
content: Hmmm, I sense a product opportunity here.For those who prefer a pristine scope, adhesive, kevlar BNC rings for those oscilloscopes without auto-attenuation rings. (patent pending)Just like those old paper re-enforcement rings but bigger

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 12:06:55 pm
content: Quote from: Fungus on August 20, 2019, 11:44:10 amAs people seem to stop reading after that phrase I've edited the original post. It's not about attenuation sensing.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 12:08:35 pm
content: Quote from: BillB on August 20, 2019, 12:05:33 pmMaybe.I'm just trying to figure out whether I'm an idiot overlooking something or whether marring is indeed expected and intended

author: Fungus
author_rank: Super Contributor
timestamp: August 20, 2019, 12:14:03 pm
content: Quote from: Mr. Scram on August 20, 2019, 12:06:55 pmI know, it's about scratching.Those proves are more expensive so I don't think they're normally supplied with non-sensing-enabled 'scopes.ie. It's mostly somebody else's problem.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 20, 2019, 12:25:48 pm
content: Quote from: Fungus on August 20, 2019, 12:14:03 pmThe most prominent example I could find are the probes pictured supplied with the Keysight 2000X series. Those oscilloscopes don't have sensing rings yet come with probes with pins. Maybe Daniel Bogahasselhoff can tell us more about what the considerations for supplying that combination are.

author: Fungus
author_rank: Super Contributor
timestamp: August 20, 2019, 01:35:57 pm
content: Quote from: Mr. Scram on August 20, 2019, 12:25:48 pmProbably need to start a thread with "Why does Keysight....?" in the name for Daniel to notice it.

author: tautech
author_rank: Super Contributor
timestamp: August 20, 2019, 08:31:18 pm
content: Quote from: Mr. Scram on August 20, 2019, 12:25:48 pmReally ?

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 09:55:38 am
content: Quote from: Fungus on August 20, 2019, 01:35:57 pmI shot him a message for some input on at least the Keysight part of the story. Other manufacturers aren't on here so I suppose we won't hear from them.

author: Vaiti
author_rank: Contributor
timestamp: August 21, 2019, 10:33:37 am
content: Wasn't there a Rohde and Schwarz rep kicking around on the forums?https://www.eevblog.com/forum/profile/?u=133086

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 10:57:44 am
content: Quote from: Vaiti on August 21, 2019, 10:33:37 amThe Rohde and Schwarz models without probe sense rings seem to come with RT-ZP03 probes which don't have a pin.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: August 23, 2019, 04:32:58 pm
content: A couple comments. The pin is useless to scopes without the sense ring on the inputs. I haven't heard of any complaints with Keysight probes scratching up the plastic of scopes, but that doesn't mean it hasn't/wont happen. The pin is spring-loaded with the intent that it will make contact but not do damage. Of course, we don't really spec in other manufacturer's plastics, etc. when we're looking at the pin.Essentially, there's a sense resistor behind that pin that the scope looks for. The scopes have a list internally of different resistance values and sets attenuation according to the resistance value. In that sense it's vendor specific, but there seems to be some conventional practices around the resistor values of common probes.The unofficial guidance on these pins is that, if you don't need them and won't need them, just pull it out with some pliers and it won't impact anything. Pogo pins like that typically can be popped in/out a couple times without damage.We use BNC connectors for most low and mid-range probes because the technology is well defined and priced reasonably. We do have some higher end BNC tech we use (precision BNC) to get better connections and longer BNC life. But, as bandwidths increase you'll start to see different connectors (like the 1mm on the 110 GHz UXR Series Scopes).

author: Fungus
author_rank: Super Contributor
timestamp: August 25, 2019, 11:33:04 am
content: Quote from: Keysight DanielBogdanoff on August 23, 2019, 04:32:58 pmGood point. Surely the pins should be nicely rounded and lightly sprung so they don't scratch. You don't want to wear out the contact areas on the 'scope they're supposed to attached to.

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2019, 02:28:09 pm
content: In the past it was common for oscilloscopes which did not support probe readout to be designed to accept probes with the readout function without damaging or marring the oscilloscope.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 25, 2019, 06:02:52 pm
content: Quote from: Keysight DanielBogdanoff on August 23, 2019, 04:32:58 pmThanks for your input! What kicked this thread off was the specific listing linked below which lists a mint Keysight 2000X series oscilloscope bar some scratches created by probe pins. As this mirrored my own past experience with this model range it piqued my interest. I wasn't aware the pins can actually be removed from the probes even if it's not officially recommended.https://www.eevblog.com/forum/buysellwanted/(us-only)-keysight-dsox2014a-wwarranty/

author: Gyro
author_rank: Super Contributor
timestamp: August 25, 2019, 06:17:43 pm
content: Quote from: David Hess on August 25, 2019, 02:28:09 pmNot with HP, a lot of them had the BNC nut on the outside.

author: David Hess
author_rank: Super Contributor
timestamp: August 26, 2019, 05:14:46 am
content: Quote from: Gyro on August 25, 2019, 06:17:43 pmHP's marketing was big on disparaging Tektronix for adding superfluous bells and whistles like probe readout.