Compatible Probes - Page 1
Forum section: electronics / testgear

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 04:43:37 am
content: HiI have a new Siglent SDS1102CNL 100mHZ scope which I am starting to play with (Noob here).I want a probe to BNC adaptor to assess my bench power supply but they are difficult to come by here in OZ.One alternative is to by a new probe kit from Elenco which is a 250MHz probe with adaptors. It has the spec below. Can someone please confirm that its spec is compatible with the scope as I am not 100% sure that the two specs are talking the same language with regard to impedance, capacitance and compensation. I am also assuming that there are no negative consequences of using a probe with a higher frequency spec? I also note that adaptors for Agilent probes are specified as 5mm, but I measure the probe ground of the Siglent probes as ~4.5mm - what gives?I have made enquires with Siglent but the first reply from the contact just wanted to sell me another Siglent probe - language confusion no doubt.Thanks in advance.POSITION - X10Attenuation Ratio 10:1Bandwith DC to 250MHzRise Time 1.4 nSInput Impedance 10M ohm when used with oscilloscopes with 1M ohm inputInput Capacitance Approx. 17pFCompensation Range 10 to 35pFCompensation Range 10 to 35pFWorking Voltage 600V CAT I; 300V CAT II (DC + peak AC) derating with frequencyProbe tip grounded via 9M ohm resistor ; oscilloscope input groundedPOSITION - X1Attenuation Ratio 1:1Bandwidth DC to 6MHzRise Time 58nSInput Impedance 1M ohm (oscilloscope input)Input Capacitance 47pF plus oscilloscope capacitanceWorking Voltage 300V CAT I; 150V CAT II (DC + peak AC) derating with frequencyOperating Temperature -50 F (-10 C) to 131 F (55 C)Humidity 85% RH or less (at 95 F/ 35C)Safety Meets EN61010-031 CATII

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 05:14:31 am
content: If I have this right you are referring to the BNC adapter that slips on to the probe tip when the hook end is removed?And yes they are specific diameters for specific probes.In my experience they only come with higher spec probes.I have 300 MHz probes and 100:1 probes with them.They can be useful, but are no replacement for a proper BNC cable.If you must have one, I suggest you acquire a100:1 probewith one as 100:1 probewillbe of use for any HV work you may do.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 07:12:58 am
content: Yes that is the item. BNC one end, socket to take prove tip minus hook.The spec I posted was an Elenco probe for $40AU.Can you suggest a 100:1 probe that doesn't cost a substantial fraction of the scope value?Are you suggesting that I connect the scope to power supply by simply using a BNC cable? - sounds easier! I have the banana plug to BNC connector already.

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 07:40:10 am
content: This probe is not much more and local to you:http://www.jaycar.com.au/productView.asp?ID=QC1903&form=CAT2&SUBCATID=1062#1And it has the adapter.The spec of your posted probe and the one I have linked will suit your SDS1102CNLYes you can connect directly, it is the same as a 1:1 probe that is: 1 M Ohm input.Don't forget to select AC coupling to measure ripple.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 07:55:14 am
content: Thanks, I did see that one, after I posted - 1/4 of my scope cost - I am so tight fisted

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 08:03:21 am
content: Quote from: Dunk_c on August 05, 2014, 07:55:14 amIt will not seem much if you do any HV and thereby risk hurting your scope or yourself.IMO 100:1 is needed for all work at anything like mains potential.Be safe and don't put your hard earned gear at risk.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 08:16:07 am
content: Sage advice - thanks.Another question or two.If i connect the scope to power supply with a BNC cable, I read somewhere that I need to terminate the connection at the scope with a t-fitting and a 50 ohm resistor - is this correct?One thing I want to do is check the quality of the output of my 12-240v pure sine wave inverter. It will be floating without direct connection to ground. Are there any risks associated with connecting the scope directly to the socket of the inverter?

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 08:33:24 am
content: Quote from: Dunk_c on August 05, 2014, 08:16:07 amWhoaMany risks to scope and yourself.OP was bench power supply.Now stop and think.Definitely not without at least 10:1 probe. AC coupling.Check for float between scope BNC outer(mains earth) and inverter earth(this will be where scope reference clip will connect).Check inverter earth and neutral are common in case you need to reference from neutral.Be very careful and think safety first and result second.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 09:06:55 am
content: Maybe I should have started another post to keep the info for each test separate and not confuse anyone - my mistake.There is no connection of inverter to earth as it is an isolated PV system with batteries.I need to do more research - obviously!

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 09:16:05 am
content: Quote from: Dunk_c on August 05, 2014, 09:06:55 amJust be careful.I don't want a fried Dunk_c on my conscience.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 09:26:08 am
content: Appreciate your concern. This Dunk_c has previous experience with electric shocks and doesn't want a replay!Garden lighting transformers are, as far as I know, isolated 240-12v. These appear to be a good DIY route to having a cheap isolation solution in an enclosed package. Using this I could monitor mains power wave forms under load with an attenuated amplitude but faithful waveform - is this a reasonable assumption?

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2014, 09:41:58 am
content: Quote from: Dunk_c on August 05, 2014, 09:26:08 amAny ordinary mains to LV transformer should do.You can monitor the HV AC with a DMM and check the waveform with the scope at LV.The transformer may dampen some signals before you see them on LV, but the fundamental waveform remains the same.

author: Dunk_c
author_rank: Contributor
timestamp: August 05, 2014, 09:56:13 am
content: I'll just use an AC wall wart and see what it looks like. Thanks for the chat tonight.