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Test Equipment / Re: Used multimeter buyer's guide
« Last post by EEVblog on Today at 09:57:09 PM »
Thinking about just getting this one.  It's $8 and the AD584L.  They also measure with a 6 digit calibrated multimeter, at all four voltages: 2.5, 5, 7.5 & 10V.  And they share their results on the bottom on a label.  All you have to do is dial in your meter to match their numbers.

Beware, not all meters can be calibration adjusted that easily. They might need specific voltages and all ranges done, not just individual.
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Also, be wary of MEMS magnetomers - you REALLY need to calibrate them, or at least have some compensations. The individual axis have wildly different offsets and gains - you can get an error of 30deg when calculating the magnetic heading from a raw uncalibrated magnetomer, at least that was the case in LSM9DS0 which I used. Calibration/compensation is a relatively simple matter.
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General Chat / Re: Advice on cheap Linux computer for my kids
« Last post by SingedFingers on Today at 09:55:38 PM »
Watch out for the workstation class machines; they drink electricity :)
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Test Equipment / Re: Used multimeter buyer's guide
« Last post by EEVblog on Today at 09:54:58 PM »
The Instek GDM-8251A you mentioned is so tempting.  I see one in like new condition on ebay for $120 shipped.

http://www.ebay.com/itm/GW-Instek-120-000-Counts-Dual-Display-Multimeter-GDM-8251A-/291980567514

US$110 each seems like a bargain. GW Instek make decent gear. Not Keysight/Fluke/Keithley level of course, but decent.

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It is, as far as I know, parasitic oscillation and can destroy transistors.

It's a problem with RF MOSFETs too, the simple cure is the same, add a resistor to the gate but that's not a guarantee, with parts that can do GHz or even VHF you need to be very careful of board layout and construction because it's not unheard of to find you're emitting significant power at some very unexpected frequencies.

It's better to choose a more suitable transistor (lower Ft) if possible but the number of Bipolar RF transistors available these days makes that less simple.

If you really only need half a watt at <30MHz and can use through hole parts then there are many CB transistors available, there's even the BD139 which is a dirt cheap part and is capable of a couple of watts if you heatsink it and drive it properly. 
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Circuit Studio / Re: Half price Circuit Studio
« Last post by EEVblog on Today at 09:51:07 PM »
The price is 464€ from element14. So it is the same as 499$ eagle discount price https://www.element14.com/community/docs/DOC-73745/l/circuitstudio-altiums-professional-pcb-tool

Yep, seems like the Eagle deal is not special, it's just the current regular price (for now).
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Circuit Studio / Re: Half price Circuit Studio
« Last post by EEVblog on Today at 09:49:06 PM »
Why does CS not support Allium binary files?
Cause making a product pyramid (AKA stupid business decisions).
If you would like to know more, just mention it to Mr. Dave Jones...

Altium are pyramid masters!







Bonus triangles!
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Other Equipment & Products / Re: Cheap Chinese ceiling LED lamp teardown
« Last post by nctnico on Today at 09:48:51 PM »
The beam isn't very wide so I probably need several to get an even light distibution.
Or buy one decent one  ;)
From where? I'd probably get a crappier lamp with a safety rated driver for 3 times the price if I go to a local shop.

This looks awfully familiar:
https://www.ledsrefresh.nl/nl/led-downlight-vierkant/platte-led-downlighter-vierkant-25w
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you can easily custom make it. Just use a suitable size cable gland with the thread and a spring test pin in the centre, epoxy the assembly with wire out of the assembly.
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Even with a fully functional instrument with more than adequate performance, an engineer will test their understanding and how it interacts with the circuit.

Exactly, understanding (of staying within spec)! Engineer cannot be forced to create spec. Full spec for simplest instrument can be quite extensive. Following your logic there is no need for spec at all - just give engineer a "black box" and do not count on him for year until he is mapping the thing  :-DD

How long it would take to create in full detail, this small outtake from U1282A spec? Now sum individual time for each engineer that has the thing, each one individually spending time to spec it   :palm:


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