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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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A useful addition to your toolkit
https://www.sparkfun.com/products/11005
Replace the existing connector with a BNC, add a bit of series resistance and you have a *very* cheap current probe for your scope. |
#2
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A useful addition to your toolkit
On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
wrote: https://www.sparkfun.com/products/11005 Replace the existing connector with a BNC, add a bit of series resistance and you have a *very* cheap current probe for your scope. I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. My real problem with current measurement is DC, on PC boards. We want to know how much current, say, an FPGA is using. Sometimes I include current shunts in a layout, but sometimes I don't. One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#3
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A useful addition to your toolkit
On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote:
I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. Indeed they're not. But your meter is presumably *only* designed for use at 60Hz, I would imagine. Hook it up to a 100Hz signal and you'll see nothing at all in all probability. ;-) One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. Do they even exist? That would be amazing but no doubt *way* beyond what I can justify to splash out on as a mere hobbyist. |
#4
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A useful addition to your toolkit
On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom
wrote: On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote: I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. Indeed they're not. But your meter is presumably *only* designed for use at 60Hz, I would imagine. Hook it up to a 100Hz signal and you'll see nothing at all in all probability. ;-) One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. Do they even exist? That would be amazing but no doubt *way* beyond what I can justify to splash out on as a mere hobbyist. A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp makes 25 millivolts, and lots of cheapish DVMs will resolve that well enough. You probably need a bench DVM with microvolt resolution to measure, say, 1 amp running through a via, but you could build a little microvolt meter or amp pretty easily. PCB trace and via resistances need to be calibrated, which is only a minor nuisance. Here are some pcb-trace shunts, down near the connector: https://dl.dropboxusercontent.com/u/...ower_Board.JPG One of the great mysteries of electronics is "where is the current going?" Sometimes a thermal imager helps figure that out. A little magnetometer would be fun, not hard to do these days. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#5
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A useful addition to your toolkit
On 05/03/2017 15:44, John Larkin wrote:
I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. Tell that to a condition monitoring engineer! |
#6
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A useful addition to your toolkit
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#7
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A useful addition to your toolkit
They do make special current probes specifically for doing traces
on a PC board. without cutting traces or requiring a loop of wire. http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com |
#8
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A useful addition to your toolkit
On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile
wrote: They do make special current probes specifically for doing traces on a PC board. without cutting traces or requiring a loop of wire. http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf Looks expensive, and I'd guess not very accurate. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#9
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A useful addition to your toolkit
On 3/5/2017 3:37 PM, John Larkin wrote:
Looks expensive, and I'd guess not very accurate. http://www.aimtti.us/product-category/current-probes/aim-i-prober-520 It is expensive. At $795 for the basic probe. Data sheet: http://resources.aimtti.com/datasheets/prec-iprober520-5p.pdf Instruction manual: http://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss5.pdf -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com |
#10
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A useful addition to your toolkit
Foxs Mercantile wrote...
John Larkin wrote: Looks expensive, and I'd guess not very accurate. http://www.aimtti.us/product-category/current-probes/aim-i-prober-520 It is expensive. At $795 for the basic probe. Data sheet: http://resources.aimtti.com/datasheets/prec-iprober520-5p.pdf Instruction manual: http://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss5.pdf The expense we can handle, if, for example, it'll give us adequate help in debugging our switching power supply designs. But the calibrating scheme for trace current measurements looks iffy. But maybe along with other measurements, power in, voltage and power out, etc., it could do the job. It is fast enough to look at inductor currents. -- Thanks, - Win |
#11
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A useful addition to your toolkit
On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin
wrote: On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom wrote: https://www.sparkfun.com/products/11005 Replace the existing connector with a BNC, add a bit of series resistance and you have a *very* cheap current probe for your scope. I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. My real problem with current measurement is DC, on PC boards. We want to know how much current, say, an FPGA is using. Sometimes I include current shunts in a layout, but sometimes I don't. I generally use a ferrite (pi filter) on the supplies to uCs and DSPs for EMI, then substitute a shunt to measure the power during test. One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. The old HP current probe was a great debugging tool. |
#12
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A useful addition to your toolkit
John Larkin wrote:
I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. ** Mains current waveforms are VERY interesting, but not if all you can see is 60Hz. A Hall effect transducer is needed to do the job properly. The one is use is by LEM and has response to 100kHz, allows me to see currents as low as 1mA and up to 100A peak. ..... Phil |
#13
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A useful addition to your toolkit
On Sun, 05 Mar 2017 19:56:44 +0000, JM
wrote: On 05/03/2017 15:44, John Larkin wrote: I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. Tell that to a condition monitoring engineer! I don't design AC power supplies any more. I can buy an entire nice PFC switcher for less than I could buy a 60 Hz power transformer. Since the supplies all come with UL/CE/VDE/etc stickers, I don't care about their input current waveforms. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#14
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A useful addition to your toolkit
On 3/5/2017 4:37 PM, John Larkin wrote:
On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile wrote: They do make special current probes specifically for doing traces on a PC board. without cutting traces or requiring a loop of wire. http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf Looks expensive, and I'd guess not very accurate. Seems to me it would be a *great* tool for finding where the currents are going. I thought that would be a good thing? -- Rick C |
#15
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A useful addition to your toolkit
On 3/5/2017 11:58 PM, rickman wrote:
Seems to me it would be a *great* tool for finding where the currents are going. I thought that would be a good thing? It is. But some people have difficulty accepting anything more complicated than a light bulb, or more expensive than a pack of cigarettes. -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com |
#16
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A useful addition to your toolkit
On 3/6/2017 1:56 AM, Foxs Mercantile wrote:
On 3/5/2017 11:58 PM, rickman wrote: Seems to me it would be a *great* tool for finding where the currents are going. I thought that would be a good thing? It is. But some people have difficulty accepting anything more complicated than a light bulb, or more expensive than a pack of cigarettes. You mean like thermal cameras? -- Rick C |
#17
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A useful addition to your toolkit
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#18
Posted to sci.electronics.design,sci.electronics.repair
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A useful addition to your toolkit
On Mon, 06 Mar 2017 00:56:56 -0600, Foxs Mercantile wrote:
It is. But some people have difficulty accepting anything more complicated than a light bulb, or more expensive than a pack of cigarettes. For the *real* cheapskates out there, there's this alternative: http://www.ebay.com/itm/100A-SCT-013...urrent-sensor- Split-Core-Transformer-YH-/201842524936? hash=item2efec08308:g:vm8AAOSwCGVX3BYF Claims to be able to handle up to 100A! |
#19
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A useful addition to your toolkit
On Mon, 6 Mar 2017 00:56:56 -0600, Foxs Mercantile
wrote: On 3/5/2017 11:58 PM, rickman wrote: Seems to me it would be a *great* tool for finding where the currents are going. I thought that would be a good thing? It is. But some people have difficulty accepting anything more complicated than a light bulb, or more expensive than a pack of cigarettes. It's not hard to figure where current is going: just measure voltage drops. What's sometimes difficult is quantifying it. Just now we're laying out a 10-layer board with two ground planes and three power planes. There are 22 power supplies. Most of the power distribution will be interestingly-shaped interleaved pours, not traces, on various layers. That magnetic gadget would be hopelessly confused. Multiple currents and various return paths would make it useless. My favorite tool for tracing unusual current flows is my Flir E45 thermal imager. It cost $12,000. We just demoed a cool new thermal imager, mounted on a nice little stand, with its own display and also USB interfaced for pics or movies. They're going to let us keep it. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#20
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A useful addition to your toolkit
Cursitor Doom wrote:
On Mon, 06 Mar 2017 00:56:56 -0600, Foxs Mercantile wrote: It is. But some people have difficulty accepting anything more complicated than a light bulb, or more expensive than a pack of cigarettes. For the *real* cheapskates out there, there's this alternative: http://www.ebay.com/itm/201842524936 Claims to be able to handle up to 100A! Let's see you use it to find a stray 100 mA DC on a crowded circuit board. -- Never **** off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
#21
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A useful addition to your toolkit
John Larkin wrote...
We just demoed a cool new thermal imager ... Names, please. And results, later. -- Thanks, - Win |
#22
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A useful addition to your toolkit
"Winfield Hill" wrote in message news John Larkin wrote... We just demoed a cool new thermal imager ... Names, please. And results, later. -- Thanks, - Win We don't believe it until there are pictures. |
#23
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A useful addition to your toolkit
On 6 Mar 2017 18:06:30 -0800, Winfield Hill
wrote: John Larkin wrote... We just demoed a cool new thermal imager ... Names, please. And results, later. I'm not sure I can name names yet. It's still in development. We've become sort of a beta tester for these people. They send us units and get our feedback, and we can keep them. Or maybe they just like coming to San Francisco. -- John Larkin Highland Technology, Inc lunatic fringe electronics |
#24
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A useful addition to your toolkit
Phil Allison wrote:
John Larkin wrote: I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. ** Mains current waveforms are VERY interesting, but not if all you can see is 60Hz. A Hall effect transducer is needed to do the job properly. The one is use is by LEM and has response to 100kHz, allows me to see currents as low as 1mA and up to 100A peak. .... Phil I used to like using a Tek Hall sensor probe. I liked it checking DC shorts on boards. Greg |
#25
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A useful addition to your toolkit
On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz
wrote: I used to like using a Tek Hall sensor probe. I liked it checking DC shorts on boards. Greg Yes, but have you seen the prices? http://www.tek.com/current-probe The cheapest model that does DC is $1,600. I rolled my own. I took an old Honeywell SS495A Hall effect sensor, built a suitable amplifier, hot melt glued it to a piece of plastic, and calibrated it by shoving DC through various PCB traces. It's ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near magnetic fields from xformers, inductors, steel mounting brackets, wall warts, etc. However, it's cheap and easy. I don't use it for troubleshooting very often. The original suggestion sounds much like an RF current probe. http://www.lowfer.us/k0lr/currprob/currprob.htm https://interferencetechnology.com/the-hf-current-probe-theory-and-application/ However, these cannot be used to measure current though a PCB trace. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#26
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A useful addition to your toolkit
On Mon, 06 Mar 2017 20:56:02 -0500, Michael A. Terrell wrote:
Let's see you use it to find a stray 100 mA DC on a crowded circuit board. Oh come along now. You know it's not intended for that sort of usage! |
#27
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A useful addition to your toolkit
On Mon, 06 Mar 2017 20:56:00 -0800, John Larkin wrote:
Or maybe they just like coming to San Francisco. Unlikely. ;- |
#28
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A useful addition to your toolkit
Jeff Liebermann wrote:
On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz wrote: I used to like using a Tek Hall sensor probe. I liked it checking DC shorts on boards. Greg Yes, but have you seen the prices? http://www.tek.com/current-probe The cheapest model that does DC is $1,600. I rolled my own. I took an old Honeywell SS495A Hall effect sensor, built a suitable amplifier, hot melt glued it to a piece of plastic, and calibrated it by shoving DC through various PCB traces. It's ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near magnetic fields from xformers, inductors, steel mounting brackets, wall warts, etc. However, it's cheap and easy. I don't use it for troubleshooting very often. The original suggestion sounds much like an RF current probe. http://www.lowfer.us/k0lr/currprob/currprob.htm https://interferencetechnology.com/the-hf-current-probe-theory-and-application/ However, these cannot be used to measure current though a PCB trace. I was using a NASA owned probe. Thought about trying to make one. Greg |
#29
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A useful addition to your toolkit
Cursitor Doom wrote...
Michael A. Terrell wrote: Let's see you use it to find a stray 100 mA DC on a crowded circuit board. Oh come along now. You know it's not intended for that sort of usage! I ordered one from Newark, and plan to use it on my messed-up switching power-supply designs. Qualitative results will be fine. -- Thanks, - Win |
#30
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A useful addition to your toolkit
On Wed, 08 Mar 2017 05:44:39 -0800, Winfield Hill wrote:
I ordered one from Newark, and plan to use it on my messed-up switching power-supply designs. Qualitative results will be fine. Mine arrived today. I plan to monitor fuel injection impulses with it firstly just to see what kind of di/dt responses it's capable of. I'm not quite as confident as you are, though! |
#31
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A useful addition to your toolkit
Cursitor Doom wrote...
On Wed, 08 Mar 2017 05:44:39 -0800, Winfield Hill wrote: I ordered one from Newark, and plan to use it on my messed-up switching power-supply designs. Qualitative results will be fine. Mine arrived today. I plan to monitor fuel injection impulses with it firstly just to see what kind of di/dt responses it's capable of. I'm not quite as confident as you are, though! I do a lot of fast HV pulsing circuitry, and don't expect it'll be helpful for that kind of work. But the 5MHz bandwidth should be fine for looking at inductor current ramps, cap charge-discharge, etc. -- Thanks, - Win |
#32
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A useful addition to your toolkit
On 2017-03-08, Winfield Hill wrote:
Cursitor Doom wrote... Michael A. Terrell wrote: Let's see you use it to find a stray 100 mA DC on a crowded circuit board. Oh come along now. You know it's not intended for that sort of usage! I ordered one from Newark, and plan to use it on my messed-up switching power-supply designs. Qualitative results will be fine. a few years back there was talk of using a video head from a VCR (after removing it from the drum) to probe AC currents. It should be good to a few megahertz. a core from an ethernet transformer with a gap added could be another option. a spool-shaped inductor would probably work too. -- This email has not been checked by half-arsed antivirus software |
#33
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A useful addition to your toolkit
On 8 Mar 2017 18:53:52 GMT, Jasen Betts wrote:
On 2017-03-08, Winfield Hill wrote: Cursitor Doom wrote... Michael A. Terrell wrote: Let's see you use it to find a stray 100 mA DC on a crowded circuit board. Oh come along now. You know it's not intended for that sort of usage! I ordered one from Newark, and plan to use it on my messed-up switching power-supply designs. Qualitative results will be fine. a few years back there was talk of using a video head from a VCR (after removing it from the drum) to probe AC currents. It should be good to a few megahertz. a core from an ethernet transformer with a gap added could be another option. a spool-shaped inductor would probably work too. A little unshielded drum-core inductor is a handy h-field probe. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com |
#34
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A useful addition to your toolkit
On Tuesday, March 7, 2017 at 1:21:14 PM UTC-5, Cursitor Doom wrote:
On Mon, 06 Mar 2017 20:56:00 -0800, John Larkin wrote: Or maybe they just like coming to San Francisco. Unlikely. ;- Maybe they could not find any flowers : https://www.youtube.com/watch?v=bch1_Ep5M1s Sorry I did not get the studio version, but this one looks interesting. But I hate to say it, you will never catch me dead anywhere in California. Maybe fifty years ago but not today, even if I could afford the rents there. |
#35
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A useful addition to your toolkit
John Larkin wrote:
On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom wrote: https://www.sparkfun.com/products/11005 Replace the existing connector with a BNC, add a bit of series resistance and you have a *very* cheap current probe for your scope. I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. My real problem with current measurement is DC, on PC boards. We want to know how much current, say, an FPGA is using. Sometimes I include current shunts in a layout, but sometimes I don't. One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. You just described that PCB trace current probe; just use known trace length - with known width you get approximate current. |
#36
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A useful addition to your toolkit
On Thu, 09 Mar 2017 22:43:29 -0800, Robert Baer
wrote: John Larkin wrote: On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom wrote: https://www.sparkfun.com/products/11005 Replace the existing connector with a BNC, add a bit of series resistance and you have a *very* cheap current probe for your scope. I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. My real problem with current measurement is DC, on PC boards. We want to know how much current, say, an FPGA is using. Sometimes I include current shunts in a layout, but sometimes I don't. One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. You just described that PCB trace current probe; just use known trace length - with known width you get approximate current. I do that. But multi-layer power pours are not such well-defined resistors. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com |
#37
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A useful addition to your toolkit
On Wed, 08 Mar 2017 22:58:08 -0800, jurb6006 wrote:
Sorry I did not get the studio version, but this one looks interesting. Certainly did! But I hate to say it, you will never catch me dead anywhere in California. Maybe fifty years ago but not today, even if I could afford the rents there. It all seemed to go tits-up right at the dog-end of 1969, around the time of the Alta Mont free concert and that awful business involving Charlie Manson and his 'Family' - and never recovered. |
#38
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A useful addition to your toolkit
John Larkin wrote:
On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom wrote: On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote: I have a clamp-on ammeter that pretty much does that, although it just indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms aren't terribly interesting. Indeed they're not. But your meter is presumably *only* designed for use at 60Hz, I would imagine. Hook it up to a 100Hz signal and you'll see nothing at all in all probability. ;-) One can use existing switcher inductors as current shunts. I wish I had a PCB trace current probe, but that's probably not posssible. You can measure millivolt and microvolt drops across traces and vias. Do they even exist? That would be amazing but no doubt *way* beyond what I can justify to splash out on as a mere hobbyist. A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp makes 25 millivolts, and lots of cheapish DVMs will resolve that well enough. You probably need a bench DVM with microvolt resolution to measure, say, 1 amp running through a via, but you could build a little microvolt meter or amp pretty easily. PCB trace and via resistances need to be calibrated, which is only a minor nuisance. Here are some pcb-trace shunts, down near the connector: https://dl.dropboxusercontent.com/u/...ower_Board.JPG One of the great mysteries of electronics is "where is the current going?" Sometimes a thermal imager helps figure that out. A little magnetometer would be fun, not hard to do these days. I once asked if a discarded head from an old, old hard disk could do that. There used to be a four-pin probe for PCB current measurement, in the late 80s, but I can't find it. They're probably on ebay but I don't know what name to search for. --- This email has been checked for viruses by AVG. http://www.avg.com |
#39
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A useful addition to your toolkit
John Larkin wrote:
On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile wrote: They do make special current probes specifically for doing traces on a PC board. without cutting traces or requiring a loop of wire. http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf Looks expensive, and I'd guess not very accurate. There's one on ebay now for $750. --- This email has been checked for viruses by AVG. http://www.avg.com |
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