10x probe recommendation - Page 1
Forum section: electronics / testgear

author: Hextejas
author_rank: Frequent Contributor
timestamp: January 27, 2018, 03:04:37 pm
content: As the subject states I need one and I see all kinds at all prices. My budget is $20.00 but could increase that if necessary.My scope is my 1st one, a self made DSO 138.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 27, 2018, 04:02:28 pm
content: I bough some Hantek PP150 probes a few years ago. They are still holding up fine.https://youtu.be/buG-H_LZH0U

author: Specmaster
author_rank: Super Contributor
timestamp: January 27, 2018, 04:12:48 pm
content: Quote from: Hextejas on January 27, 2018, 03:04:37 pmWith that scope, any 10:1 probe would suffice, you can pick them up very cheaply.

author: Peabody
author_rank: Super Contributor
timestamp: January 27, 2018, 05:21:07 pm
content: Anything you buy is going to be more capable than your scope. I found a P6000 probe, which I think is 10 MHz, for about $6 when I built my DSO150, and it works fine. You'll also find a P6020, P6040,...,P6100 in that price range. Here's a Bangood offering, also available from their US warehouse for a couple bucks more:https://www.banggood.com/DANIU-P6100-Oscilloscope-100MHz-PKCATI-BNC-Clip-Probes-Clip-Cable-p-1157611.html?rmmds=detail-top-buytogether-auto__2&cur_warehouse=CN

author: Old Printer
author_rank: Frequent Contributor
timestamp: January 27, 2018, 07:23:45 pm
content: MP Jones in Florida blows out their 20 Mhz 1-10x probes for $2.95 once and a while (right now) and I add a few to my orders. If nothing else its a nice light weight cable with a BNC connector that I attach mini grabbers and alligator clips to for the bench, when I don't need a real probe.http://www.mpja.com/20MHz-Oscilloscope-Probe/productinfo/15085+TE

author: Hydron
author_rank: Super Contributor
timestamp: January 27, 2018, 09:38:55 pm
content: The banggood type probes do not use resistive co-ax, they fake it using a ~100R resistor in the compensation box (DC resistance in 1X mode is approx. 100 ohms). This means that anything with a fast edge will ring due to the lack of damping in the cable. Unfortunately this makes them worthless for many uses - I was hoping that any issues with them would be confined to bandwidth or physical quality but they were worse than expected.

author: Specmaster
author_rank: Super Contributor
timestamp: January 28, 2018, 01:20:49 am
content: Quote from: Hydron on January 27, 2018, 09:38:55 pmWell its always been my understanding that the coax cable was just that coax and the 10:1 was achieved via 1M resistor switched in and out of series with the probe tip via the switch in the probe handle, I have no idea where you got the notion about resistive coax cable and a 100ohm resistor from?

author: joeqsmith
author_rank: Super Contributor
timestamp: January 28, 2018, 02:05:04 am
content: Quote from: Specmaster on January 28, 2018, 01:20:49 amIt's fairly well known. I think the Hantek probes are still about $10/ea. These could be used with a better scope down the road.

author: Hextejas
author_rank: Frequent Contributor
timestamp: January 28, 2018, 07:17:02 am
content: That's very impressive Joe, so I went and bought one. Not much risk.I also couldn't make up my mind on the Banggood and the MP Jones so I bought them also. I'll wind up sending 2 back.Thanks for the suggestions.

author: tggzzz
author_rank: Super Contributor
timestamp: January 28, 2018, 08:59:55 am
content: Quote from: Specmaster on January 28, 2018, 01:20:49 amDo a spice simulation of a voltage step into that circuit, and watch the transmission line "ring"!FFI, seehttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: Hydron
author_rank: Super Contributor
timestamp: January 28, 2018, 11:21:32 am
content: Quote from: joeqsmith on January 28, 2018, 02:05:04 amThanks Joe, I think i'll grab some of those next time I'm after cheap probes.For those confused about the 100 ohm thing, if you measure the DC resistance of a probe in 1X mode it'll normally be a few hundred ohms - this is from the (deliberately) lossy co-ax used to damp down ringing from the impedance mismatch such a probe will invariably present to the circuit/scope input.In the case of the banggood probes (or others which look identical - mine came from amazon) normal co-ax was used instead, probably as it was cheaper, and the probe DC resistance was from a lumped element SMD resistor in the compensation box rather than distributed resistance in a lossy co-ax cable. As the damping resistance has to be distributed to work correctly the probes were absolutely hopeless when measuring fast edges - the reflections seen on the scope were clearly from the probe rather than the circuit. See the links others have given about how probes work - it's not immediately obvious!