Hall effect scope probe?? - Page 1
Forum section: electronics / projects

author: hlavac
author_rank: Frequent Contributor
timestamp: June 22, 2020, 10:36:27 am
content: I need to trace actual magnetic field of a coil with a scope, possibly with up to 1MHz bandwidth, does anyone have a schematic / recommendation for some kind of hall effect probe i could use? Not interested in absolute precision, more like the shape of the EMF in time

author: jmelson
author_rank: Super Contributor
timestamp: June 22, 2020, 04:47:22 pm
content: Quote from: hlavac on June 22, 2020, 10:36:27 amWow, I'm not sure you can get 1 MHz out of a Hall effect device.Jon

author: hlavac
author_rank: Frequent Contributor
timestamp: June 23, 2020, 10:29:32 am
content: Yeah, may not be possible with just a hall sensor. What I need is basically what a DC/AC current clamp probe does... and those are expensive as hellMaybe there are alternative ways to measure EMF?Magnet glued to a strain gauge?Probably too low bandwidth...Or cut open a crystal and glue a tiny magnet or piece of iron / ferrite to it, watch what it does to the frequency as the magnetic field changes?

author: exe
author_rank: Unknown
timestamp: June 23, 2020, 12:21:43 pm
content: What about thishttp://electronics-diy.com/simple-emf-probe.php?EDIT there are also DIY near-field probes, I'm not sure if this those are useful:https://www.eevblog.com/forum/projects/diy-magentic-field-probes/.

author: David Hess
author_rank: Super Contributor
timestamp: June 23, 2020, 02:16:21 pm
content: Quote from: exe on June 23, 2020, 12:21:43 pmBut from the description, he needs operation down to DC which requires either a flux-gate or hall effect sensor.

author: mikerj
author_rank: Super Contributor
timestamp: June 23, 2020, 02:29:36 pm
content: Quote from: David Hess on June 23, 2020, 02:16:21 pmOr separate AC and DC probes.

author: Hydron
author_rank: Super Contributor
timestamp: June 23, 2020, 02:30:26 pm
content: Quote from: David Hess on June 23, 2020, 02:16:21 pmOr a magneto-resistive sensor, which can be obtained in DC->1MHz versions.Or just go buy a iprober 520

author: JacobPilsen
author_rank: Regular Contributor
timestamp: July 06, 2020, 11:35:19 am
content: Quote from: Hydron on June 23, 2020, 02:30:26 pmQuote from: hlavac on June 23, 2020, 10:29:32 amThat is the problem!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 06, 2020, 11:39:04 am
content: Well for DC you can't beathttps://www.ebay.ca/itm/Japanese-Magnetic-Field-Viewer-Card-Magnet-Pattern-Viewing-Film-Better-Quality/322329957791?hash=item4b0c5cd59f:g:LCIAAOSwXeJYLAZA

author: Fraser
author_rank: Super Contributor
timestamp: July 06, 2020, 12:06:38 pm
content: I may be wrong, but don’t AC/DC current clamp meters use a combination of Hall effect sensor and standard inductive coil to achieve their DC and AC capability ? An inductor would be a sensible choice of sensor for AC signals up to 1MHz. The DC and very low frequency capability would be provided by the Hall Effect device. FLUX gates also come to mind.My Toneohm short tracing units use an AC stimulus signal and tiny SMT open bobbin inductor as the browsing probes sensor. Works well at detecting the AC signal.Fraser

author: 0culus
author_rank: Super Contributor
timestamp: July 06, 2020, 05:13:54 pm
content: Quote from: hlavac on June 22, 2020, 10:36:27 amAs others have noted, if you want DC and AC response you need a probe that uses a hall sensoranda coil of some kind. I personally use an old Tek P6042 current probe, DC-50 MHz, but it's optimized for clamping on small wires for troubleshooting SMPS (and you need several of them around for parts robbery). The probe head contains both a hall effect sensor and a tiny split core transformer. I am not sure this is necessarily the right tool for your particular use case.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 07, 2020, 07:32:49 pm
content: Quote from: 0culus on July 06, 2020, 05:13:54 pmThe P6042 is a work of art more than a usable instrument. One bad drop and the transformer cracks and you no longer have a P6042. I had a perfectly working P6042 and one day a slight drop of the probe and it stopped working.I luckily managed to scrounge a NOS replacement transformer sealed with the compensation resistors but that will never happen again.And in any case the cable will break at the strain relief sooner or later.It's fun to have and if you can use yours and not break it, fine, but it's like having a Fabergé egg... For display only.

author: 0culus
author_rank: Super Contributor
timestamp: July 07, 2020, 08:58:43 pm
content: Yeah, that's why I have like...4 of them.The one I use has had the probe cable replaced with new cables. The other ones are for robbing parts from should it become necessary.

author: fmkit
author_rank: Contributor
timestamp: July 07, 2020, 09:14:49 pm
content: ACS712ELCTR-05B worked for me, just leave current sense pins floating.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 07, 2020, 10:20:32 pm
content: For AC, a VCR or hard drive head will have excellent high frequency response. A regular Hall sensor works for DC and low frequencies. Maybe all you need is to combine the two...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 08, 2020, 05:02:48 am
content: Quote from: 0culus on July 07, 2020, 08:58:43 pmI guess you got lucky, like me, and you scooped them up while the prices were low. Have you seen the prices for P6042s lately?I used to scoop up old Tek gear like a Canadair CL-215 during a forest fire. Those days are over...(See also: P6032 CF probe. Another fun one.)

author: mikerj
author_rank: Super Contributor
timestamp: July 08, 2020, 07:29:20 am
content: Quote from: Fraser on July 06, 2020, 12:06:38 pmAFAIK the AC/DC clamp meters use only a hall effect sensor but they tend to have a fairly limited bandwidth, maybe 400Hz or so.

author: 0culus
author_rank: Super Contributor
timestamp: July 08, 2020, 01:59:58 pm
content: Quote from: Alex Eisenhut on July 08, 2020, 05:02:48 amYep they are expensive. I got one of mine for an absolute song at a property auction last year.