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Søren Kjærsgaard

In January, I bought two 10V references, based on LM399. I was a bit skeptical on the design, following Marco Reps on YouTube does that to you 😂, but a teardown revealed quality components (Vishay precision resistors) and a decent circuitry and PCB layout.
I measured the standard deviation on the 10V output, using my 3458A, and I’ve done so monthly-ish ever since, leaving them powered all the time.
In March I added two more, unit 3 and 4.
Result so far: unit 1,2,3 are converging towards 1uV SDEV, unit 4 however (separate curve), started out sky-high, but it has now joined the ppm club 🤷🏼‍♂️😳
Someone mind telling me what’s going on? I mean, it’s wellknown that the noise drops over time, but why? What physical/chemical factors comes at play, causing this behavior?
#voltnuts #ppmgeek #electronicsengineering #testandmeasurement

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Søren Kjærsgaard<p>Powering up a blue laser diode to 500mW 🙂<br>Note how it acts like a poor LED until 150mA, at which point the laser process fires 🔥 </p><p>The 505B is an accurate, adjustable current source which allows for external modulation input. </p><p>It’s designed for low-noise (&lt;1.5uA RMS) and it has a photo diode input, so with a calibrated light sensor, you can achieve constant power regulation.</p><p>Last but not least: it’s designed for maximum safety with two interlock circuits, one with a physical key.<br>Its internal design has a complex redundant output circuit, which ensures that the laser will NEVER illuminate unintended and it will NEVER exceed the chosen power setting. </p><p>A fancy current source indeed, a laboratory grade instrument 🙂</p><p>This video was shot wearing the appropriate safety glasses, be VERY CAREFUL when experimenting with lasers. Even a short duration reflection at this power level WILL damage your vision 🚨‼️</p><p><a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/electronics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronics</span></a> <a href="https://techhub.social/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> <a href="https://techhub.social/tags/stem" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>stem</span></a> <a href="https://techhub.social/tags/laserfun" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>laserfun</span></a> <a href="https://techhub.social/tags/funwithlasers" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>funwithlasers</span></a> <a href="https://techhub.social/tags/ee" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>ee</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a></p>
Søren Kjærsgaard<p>Got my hands on this little gem recently, they’re hard to find in a decent state at a decent price tag. Got lucky though so now I have a dedicated laser diode driver in my lab 🤩 <br>Not super high power, it maxes out at 500mA, but it’s enough for a whole range of experiments and it has a lot of nice safety and control features 🙂<br>It’s surprisingly complex inside, but nicely built and very clean. Doubt it’s seen many hours usage, the fan is just fine 👍🏼<br><a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/laser" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>laser</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a></p>
Søren Kjærsgaard<p>This weekend was special: yesterday the baltic countries: Estonia, Lithuania and Latvia, disconnected from the Russian/Belarus 50Hz power grid, going ‘island mode’, controlling the 50Hz grid frequency themselves. </p><p>After more than a day of different stability tests, this afternoon, just before 13:00 CET, a connection to the European grid was established via Poland, so now the the three countries are in 50Hz sync with Europe. </p><p>I observed a small, undramatic, ‘burp’ in the frequency at the time of the event, and my wall socket is now in full sync with the measurement in Estonia, provided by <a href="https://techhub.social/tags/sympower" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>sympower</span></a>⚡️ 😃👌🏼</p><p><a href="https://techhub.social/tags/gridtech" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>gridtech</span></a> <a href="https://techhub.social/tags/powerdistribution" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>powerdistribution</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a></p>
Søren Kjærsgaard<p>I’ve been looking for an antenna for a permanent <a href="https://techhub.social/tags/meshtastic" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>meshtastic</span></a> node in my attic and I found this one, along with 5m RF200 low-loss cable. </p><p>I know that this setup will most likely render me ‘excommunicado’ in the <a href="https://techhub.social/tags/meshtasticcommunity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>meshtasticcommunity</span></a>: “thou shalt always install thy node right below the antenna!”, but here’s the thing: I want to experiment with different hardware, I want to do some interference measurements at night (ever heard about the ‘Mammotion’ lawnmower which illegally jams 868MHz?) , AND I have a powerful 2m/70cm transmitter close to it, and I don’t want EMI issues on a sensitive 5V line. </p><p>Besides, the antenna has 3dBi gain and I measured the cable loss to 1.4dB at 868MHz, so given its better location, the numbers still come out positive 🙂</p><p>See that dip near 145MHz btw.? Need to do a test to see how much signal it’ll pick up from my VHF rig - don’t want to damage my LoRa module 👌🏼🙂</p><p><a href="https://techhub.social/tags/lorawan" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>lorawan</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/rfengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>rfengineering</span></a> <a href="https://techhub.social/tags/rfengineer" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>rfengineer</span></a> <a href="https://techhub.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hamradio</span></a> hamr <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a></p>
Søren Kjærsgaard<p>Preparing a little curve tracer demo, walking my way through some different diodes 🙂</p><p>Starting from the left, an OA95 germanium, 1N4148, 1N4007, LEDs, a vintage 60V Selenium and finally, a zener.</p><p><a href="https://techhub.social/tags/electronics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronics</span></a> <a href="https://techhub.social/tags/testgeartuesday" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testgeartuesday</span></a> <a href="https://techhub.social/tags/rohdeschwarz" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>rohdeschwarz</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a> <a href="https://techhub.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hamradio</span></a> <a href="https://techhub.social/tags/hamr" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hamr</span></a></p>
Søren Kjærsgaard<p><a href="https://techhub.social/tags/Easterquiz" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Easterquiz</span></a>, what is this? 🐣</p><p>Correct answer and a demo will follow one of these days 🙂</p><p><a href="https://techhub.social/tags/easterfun" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>easterfun</span></a> <a href="https://techhub.social/tags/rfengineer" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>rfengineer</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>testandmeasurement</span></a> <a href="https://techhub.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hamradio</span></a> <a href="https://techhub.social/tags/hamr" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>hamr</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a></p>
Søren Kjærsgaard<p>An interferometer is a really cool laser experiment you can do at the bench 💪🏼😃</p><p>You need a laser diode with a built in photo diode sensor - not all of them have it. Keep the power low, and safe. I chose the ADL65052. <br>(Laser diodes are NOT like your common LED so if you’ve never played with them before, start with that)</p><p>Then build a transimpedance amplifier (a current to voltage amp), connect the output to an oscilloscope and here’s what happens: </p><p>The light can be reflected back into the laser, causing constructive and destructive interference. The sensor diode sees this as varying light depending on the distance to the reflector. </p><p>It’s REALLY sensitive, it’ll pick up vibrations of the surface of my bench 😳 </p><p>It’s a well described experiment, there’s a whole Wikipedia article on the principle. The physics behind it is quite sofisticated though - so it’s a neat experiment to replicate 🤓</p><p><a href="https://techhub.social/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> <a href="https://techhub.social/tags/stem" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>stem</span></a> <a href="https://techhub.social/tags/physicsfun" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physicsfun</span></a> <a href="https://techhub.social/tags/stemeducation" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>stemeducation</span></a> <a href="https://techhub.social/tags/electronics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronics</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>electronicsengineering</span></a> <a href="https://techhub.social/tags/engineer" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>engineer</span></a></p>
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