<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Actually I remember my first multimeter (a very crappy one) used to do that, <div class=""><br class=""></div><div class="">Forward voltage went up as I kept measuring </div><div class=""><br class=""></div><div class="">It also did that when measuring capacitors . Maybe it has to do with diode capacitance ? Just a stupid guess</div><div class=""><div><br class=""><blockquote type="cite" class=""><div class="">Le 10 avr. 2020 à 20:19, ColinMuirDorward <<a href="mailto:colindorward@gmail.com" class="">colindorward@gmail.com</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">Others will have more informed feedback, but did you rule out temperature changes as the cause of your measurement drifts?</div><div class=""><br class=""></div><div class="">Colin<br class=""></div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Apr 10, 2020 at 4:48 PM Didier Leplae via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class=""><div style="font-family:verdana,helvetica,sans-serif;font-size:13px" class=""><div dir="ltr" class="">Does anyone have thoughts on the best way to do diode matching? </div><div dir="ltr" class="">I am building some ring modulators and need matched 4148 diodes, or similar.</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class="">So far I have tried three different methods of testing and find the results to be confusing and unreliable.</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class=""> The first method I tried was using a <a href="https://www.amazon.com/Transistor-DROK-Capacitor-Capacitance-Automatic/dp/B01MS1FOYM" target="_blank" class="">DROK transistor tester</a> (which also tests diodes). I taped a strip of new 4148 diodes to a sheet of paper in a notebook and one by one wrote down the results. I noticed that most of them had pretty similar results, but there were a few outliers that had wildly higher readings (forward voltage drop, I think). So, out of curiosity I went and tested those again and found that the readings the second time were much more similar to the others. </div><div dir="ltr" class=""> Then I started rechecking all of them and found that I was getting a completely different set of readings. The differences between readings on any one diode seemed to vary as much as differences between diodes. And as I rechecked diodes I kept getting different results.</div><div dir="ltr" class=""> So, I concluded that my transistor tester must not be very good.<br class=""></div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class=""> I then tried a the second method which is the diode testing setting on <a href="https://www.etekcity.com/product/100111" target="_blank" class="">my Etekcity multimeter</a>. This time I found that all the diodes read pretty much the same forward voltage drop. (They seem to increase slightly the more diodes I tested but if I go back to the first diode, for example, the reading will be at the same increased value). I came back later and tested again, this time the results were similar in that they all read the same value, except the value was 100mV or so lower. And again if I came back the next day similar results. So, I concluded that my multimeter's diode testing mode might be unreliable.<br class=""></div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class=""> I then tried the third method of using the voltmeter, in mV setting, to test forward voltage drop. Since my voltmeter's mV setting only goes to 2000mV, I used a 1.5V AA battery and a 10k resistor (to give about 0.15mA) in series with my diode. The results were quite similar to the readings I was getting using the diode testing mode on the multimeter. The values in one set of tests would be virtually identical for all of the diodes, but if I come back and test again they are quite different from the previous value, but the same for all diodes.</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class="">I'm pretty confused by all of this. Do I just have a crappy multimeter? Or are my diodes all miraculously matched?</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class="">Any thoughts would be helpful. </div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class="">Thanks,</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class="">Didier</div><div dir="ltr" class=""><br class=""></div><div dir="ltr" class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div dir="ltr" class=""> </div></div></div>_______________________________________________<br class="">
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