What is the best deal for the current probe for the scope?  - Page 1
Forum section: electronics / testgear

author: dimbmw
author_rank: Regular Contributor
timestamp: July 15, 2020, 06:48:21 am
content: I'd like it to be compact and measure with reasonable accuracy, let's say up to 200 kHz, with BNC connector to attach it to the scope input. 1mA and up is OK.I think my mental limit is around $300.Thanks!

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2020, 08:16:36 am
content: Quote from: dimbmw on July 15, 2020, 06:48:21 amGood luck with that.Rather than investing in many of the new offerings pick up one of the great old Tek P6021 or P6022 current probes.Here's my P6021 checked on a DF2001A deskew fixture that provides 147mA square wave @ ~22 KHz.This in probe termination 2mA/mV setting, the more sensitive compared to it's 10mA/mV.

author: Hydron
author_rank: Super Contributor
timestamp: July 15, 2020, 11:33:49 am
content: if you need DC and 1mA resolution then good luck with that, you're probably an order of magnitude off in your price expectations for anything other than getting lucky on a 25+ year old tektronix probe from ebay (and by lucky i mean in both the auction and in getting a working unit, as known good probe+amplifier combos normally go for more than your budget so you'll be rolling the dice on "as-is" units). AC probes like those suggested above are cheaper - also look for 1V/A "Current Monitors" from Pearson, but they'll still be a few hundred bucks unless you're lucky.DIY wise, if AC is ok and you don't have wide bandwidth requirements (e.g. if you need up to 200kHz+ but only down to say 20kHz), and don't need a clamp-on solution, you can probably DIY a probe for $10. DC you might scrape by with a LEM current sensor or something - they are normally specced to about 200kHz and a low-range unit might just get you 1mA resolution, though again with no option for clamp-on.

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2020, 12:20:19 pm
content: The CP-05A (4A / 40A range) is reasonable but don't expect 1mA resolution. It seems the less ranges a current probe has, the lower the noise but don't expect miracles. The probes Tautech suggests are AC only. Measuring AC current is much easier.

author: Martin72
author_rank: Super Contributor
timestamp: July 15, 2020, 12:39:02 pm
content: QuoteHands away from this !It´s noisy like hell ( forget measuring under 1A)....I got this one.You can´t expect getting 1mA resolution by spending 300$ only...But:A few weeks ago I´ve test theCP2100Bwith 1.5Mhz bandwith and up to 100A.Noiselevel was good, measurings from 50mA/div or less when using filter are possible, but don´t expect good accuracy at this low levels.The CP2100B would cost about 370 bucks, but if you don´t need the bandwith, have a look at the CP2100A.It got 800Khz bandwith and cost about 200 bucks.Martin

author: nctnico
author_rank: Super Contributor
timestamp: July 15, 2020, 01:10:31 pm
content: Quote from: Martin72 on July 15, 2020, 12:39:02 pmYou got a different version! You have the one with 4A, 40A and 400A ranges; the CP-05A with only 2 ranges performs much better. But the MicSig current probe is a good option to consider as well.

author: Martin72
author_rank: Super Contributor
timestamp: July 15, 2020, 01:23:29 pm
content: Ah, there is a version without "+", didn´t noticed that before.

author: RellikJM
author_rank: Newbie
timestamp: July 15, 2020, 02:06:44 pm
content: Take a look at the Fluke Philips PM 9355. The current probe was actually made by Tektronix for Fluke/Philips and this one on eBay fits your budget ~($200):https://www.ebay.com/itm/Fluke-Philips-PM9355-Current-Probe-and-Amplifier-5/223876311148It covers 1ma/DIV - 1A/DIV in a 1-2-5 sequence. The minimum bandwidth at the -3 dB points is 45 Mhz and the best bandwidth is 75 Mhz. It also will handle up to 12 Ap-p as long as you are above 300 HzI did a lot of searching for current probe that was low cost and high quality with good accuracy, and this is what I found and purchased myself. I don't think it's well known in the T&M community.

author: Weston
author_rank: Regular Contributor
timestamp: July 17, 2020, 01:30:09 am
content: Something to think about in terms of probe resolution: It increases the insertion impedance of the probe, but you can always increase the current resolution by adding more turns though the current probe.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 17, 2020, 02:58:00 am
content: Quote from: RellikJM on July 15, 2020, 02:06:44 pmThe PM9355 is an AC probe. The LF -3dB point is about 12Hz. It is not a Hall Effect probe that can do DC.Tektronix made a model 134 Amplifier that extends the current range and LF bandwidth of the Tektronix AC probes (P6019, P6020, P6021 and P6022).Details are here:https://w140.com/tekwiki/wiki/134Regards,Jay_Diddy_B

author: teknut
author_rank: Newbie
timestamp: July 17, 2020, 03:12:14 pm
content: I have done quite a bit of dc current probes testing myself and when you get down in the 1 mA dc range the 5 fingers on one hand are way too many to count the good ones. For the lowest cost and best performance probe an AM503B amplifier (requires a TM power supply case) plus an A6302 probe is the best there is, equal to the ones costing 5 times more as used. The older Tek amplifiers - older than a AM503B - suffers way too much from DC drift but that was resolved quite well in the AM503B. With a bit a patience and a bit of ebay luck you maybe able to get a complete set-up for some $400 - $450 buying them one by one. And yes ... 'as is' - no warranty and no return is not a good idea when it comes to such set-up since there are so many ways for it to be defective!Good Luck!A

author: Martin72
author_rank: Super Contributor
timestamp: July 17, 2020, 07:25:56 pm
content: Yes, this would be my suggestion too as I´m still waiting for a good offer in ebay for it...https://www.ebay.de/itm/Tektronix-A6302-Current-Probe-AM503A-Current-Probe-Amplifier-TM501/283939213839?hash=item421c18920f:g:bhIAAOSwnyFfAzPiActual, he wants 390€ ( answer to my price suggestion of 370).

author: Wertyuud
author_rank: Newbie
timestamp: July 18, 2020, 12:31:25 pm
content: I bougth few days ago hall current sensor for diy current probe. It ishttp://en.yhdc.com/product/HTS6(-3)-545.htmland I actually paid for it about 7.6USD. I think its quite qood for its price. Specification says it has 150kHz bandwidth, but I measured 500kHz at -1dB and about 900kHz at -3dB. The rise time is ~450ns. Only down side is that is has no split core. I will get a second sensor and investigate if its possible to split its core in half...

author: Harjit
author_rank: Regular Contributor
timestamp: July 25, 2020, 05:11:52 pm
content: I haven't come across good info. on a split core.This is an interesting approach:https://twitter.com/WestonBraun/status/1285291187595665408If you bump up to the main feed, there is some additional info.

author: Elasia
author_rank: Frequent Contributor
timestamp: July 25, 2020, 10:40:14 pm
content: Quote from: nctnico on July 15, 2020, 01:10:31 pmI found my old 2 ranger in a drawer and its still pukeI think some of it is pot luck with those things too... being so cheap and not having consistent quality partsI ran into these micsigs awhile back when looking at diff probes and was quite surprised, i have several now and they are fairly consistent, just got a second for the house and think i might get a 3rd soon for viewing multi phaseSo... you really need 1mA? You do none of this, what you do is make a current sensing resistor circuit and measure the voltage drop across it and then calculate your current from there, that is bar none the cheapest and easiest way to do it if you really need that accurate because the solution is removing the noisy hall sensors in the first place. Pre built boards targeting the flourishing arduino and pi markets are dime a dozen and cheap.. just power it and feed it to your scope

author: Weston
author_rank: Regular Contributor
timestamp: July 27, 2020, 11:08:54 pm
content: Quote from: Harjit on July 25, 2020, 05:11:52 pmThis is actually my project! It started out as just messing with a cool magnetic sensor I found and now I am working on turning it to a product to be launched on Crowd Supply at a price point somewhere around $100. As others have pointed out, there are really no good and cheap options for DC current probes, I am hoping to make that less true. Its going to be a number of months until it is a product ready for sale though.I recently created a demo album:https://www.flickr.com/photos/63341195@N08/albums/72157715180470002If you want to help shape the feature set of the final product you can help me out by filling out my market survey:https://forms.gle/2BxYyGBj3aAw4SXw7

author: thm_w
author_rank: Super Contributor
timestamp: July 28, 2020, 11:12:53 pm
content: Quote from: Weston on July 27, 2020, 11:08:54 pmWhat is the sensor used?

author: eplpwr
author_rank: Regular Contributor
timestamp: July 29, 2020, 07:24:00 am
content: Quote from: Elasia on July 25, 2020, 10:40:14 pmThis!Use a good sense resistor and an AD8421, then you can do both high-side and low side sensing. It will also work very well as a general diff probe within voltage limitations. If you want to measure a 24V rail high-side you can power the chip asymmetrically, like +30V/-5V.

author: eevcandies
author_rank: Regular Contributor
timestamp: July 30, 2020, 09:48:33 am
content: Occasionally someone, who knows nothing about it, will sell a TEK current probe setup "without" the probe. What they don't know is the second blank panel can be a pull out storage compartment...whichmayhold the missing probe. I remember someone getting one on the bay & they were pleasantly surprised to find the probe "came with it".I bought a 100 MHz Tek A6312 almost new current probe for a song...$189...found a few of the thin wires were broke right at the circular connector pins...used a 50MHz version for connection pin reference & soldered back up...works 100%

author: Weston
author_rank: Regular Contributor
timestamp: July 30, 2020, 07:57:03 pm
content: Quote from: thm_w on July 28, 2020, 11:12:53 pmIts the Honeywell HMC1041Z AMR sensor. Unfortunately, sourcing is a bit hard at the moment. Its a pretty unique part.