I opened up my PeakTech 3725 multimeter, questionable 10A conductive tracks - Page 1
Forum section: electronics / general

author: Franki
author_rank: Regular Contributor
timestamp: March 12, 2011, 08:42:20 am
content: hi thereOpening up my PeakTech 3725 3 1/2 digit multimeter reveals a supposedly maximum 10A conductive track of about 1.6 mm minimum width @70µm thickness. I'm wondering whether this may be a little too optimistic, even for a conductive track. How high would the temperature be there in theory? On the other hand, there is only one way to find out for sure...Apart from that, it actually seems a decent DMM:-V|A|Ohms calibratable(when opened) and it gets shipped calibrated-quiet acurate, though I haven't checked it against a calibrated device yet-gold plated measuring contacts on the DMM, but the shipped measuring lines aren't - this is a bit of a turn off as it doesn't make much sense :|-shielded with some metal foil (HF shielding?), but unfortunately only from the back, not the front or sides, this would make a HF-shielding pointless though :|I'm looking forward to send some pictures for you guys in the distant future.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 12, 2011, 08:56:17 am
content: PeakTech does badge engineering. That is, they get their "PeakTech" badge slaped on instruments they order from manufacturers all over the world.When you opened it, did you have an indicate who the original manufacturer of that particular meter is? Any hints on the PCB, for example?

author: Franki
author_rank: Regular Contributor
timestamp: March 12, 2011, 11:16:37 am
content: Quote from: BoredAtWork on March 12, 2011, 08:56:17 amYeah, that's well knownQuote from: BoredAtWork on March 12, 2011, 08:56:17 amI'm going to look at it as soon as I have some spare time.

author: saturation
author_rank: Super Contributor
timestamp: March 12, 2011, 12:40:57 pm
content: Pictures please, worth 1000 words.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 12, 2011, 05:55:47 pm
content: The question is no so much whether the track can take 10A but whether it can take whatever current is needed to blow the fuse without blowing first to protect the fuse.1.6mm seems rather puny.....

author: Unknown
author_rank: Unknown
timestamp: March 12, 2011, 06:37:18 pm
content: Keep in mind that it may only be rated for the full 10A for 30s or so, it may be relying on thermal inertia to keep the temperature down.

author: Neilm
author_rank: Super Contributor
timestamp: March 12, 2011, 07:47:33 pm
content: Quote from: Franki on March 12, 2011, 08:42:20 amI put the figures into a programme called MiseEL. It is a freeware programme. It says that track would rise about 40 degrees with those parameters. I have tested this in the past and againts real life currents and it is usually reasonabally accurate.Neil

author: tyblu
author_rank: Frequent Contributor
timestamp: March 12, 2011, 09:45:50 pm
content: According to the ANSI calc, which is only accurate to +100C rise, it'll have about an +180C rise.http://www.desmith.net/NMdS/Electronics/TraceWidth.htmlIs it tinned? That helps.

author: Psi
author_rank: Super Contributor
timestamp: March 12, 2011, 10:12:00 pm
content: Quote from: tyblu on March 12, 2011, 09:45:50 pmThat's for internal layers, for external layers it's only a +38C rise (for 10A through 1.6mm of 70um copper at 25C ambient).63C is hot enough to hurt if you held your finger on it, but well within what a normal pcb can handle.

author: Franki
author_rank: Regular Contributor
timestamp: March 18, 2011, 02:01:15 am
content: Quote from: alm on March 12, 2011, 06:37:18 pmI actually found a label on the scope 10A for 10sec max. This warning is realistic, but a quiet narrow PCB design...

author: Franki
author_rank: Regular Contributor
timestamp: March 19, 2011, 08:22:20 pm
content: Quote from: Neilm on March 12, 2011, 07:47:33 pmThis seems fairly acurate, though the best reliable resistive load I have in that region is a 29.5ohm 1800Watt heating coil within a water boiler for 230Veff mains which would take up about 7.8 Amps_eff...With the labeling reading 10A for 10s max, I dare not to use bigger loads.As this meter comes without any current clamp, I will need to measure the current directly. Who is sponsoring me a mains circuit opener on a male/female SchuKo plug? I already have a phasing tester.I noted another thing: the shunt in the meter is presumably made out of tin plated copper and only has a diameter of about 1.6mm or a cross-sectional surface of about 2.0mm². I wonder whether this is the weakest link in the current path...

author: Franki
author_rank: Regular Contributor
timestamp: March 19, 2011, 09:28:02 pm
content: OK, since I currently have no opportunity to make pictures of it, I'm going to describe it.The circuit is built on two different PCBs layered on top of each other but separated by about 5mm and interconnected by a soldered in 20pin single layer 2.54mm board to board pin connector which makes it impossible to see what's in between those two PCBs without unsoldering it entirelyAnd lots of other components like caps and resitors are placed at the edge of the other sides of the two PCBs (those without any board to board pin connector) so you really can't see anything in there unless you would have some kind of fibre opticsOn the bottom of one PCB are just conductive paths and on top of the other PCB are just uninteresting small jellybean ICs(low power CMOS logic, opamps...). However, there is no sign of any manufacturer at all no matter how close you may look at it, except for the forementioned jellybean ICs' manufacturersI tried doing that with a 10x magnifying glass and multiple light sources... no luck.Here are some of the ICs I recognized:NXP HEF4066BT : 4x bilateral switchtexas instrument LM358 : your standard low-power opampFairchild Semiconductor CD4093BCM : 2x smith-trigger NAND062 (?unrecognized, maybe TL062, a 2x general purpose low power opamp)072 (?unrecognized, maybe TL072, a 2x general purpose low noise opamp)model numbers/production dates/serial numbers are printed on the PCB, but no apparent manufacturer is printed on it, unless you can make it out from the abreviated codes.Front side:0731WF-668 94V0E249427UT7CA120899Back side:110899Kmostly boring stuff