martin I got the oscilloscope today. It has a "crocodile" and a hook connector:

Short impressions so far:
- The output is more accurate than (my) sound card oscilloscope. One can actually see the "zero" axis and judge how big the difference in amplitudes is. Plus the waves resemble reality much better.
- The Hz counter of the OpenHantek software is worse than the sound card scope. It seems to count only very obvious sinus waves. I.e. when the PWM almost touches the x-axis. Not sure yet how to change that.

Result of OnePlus 3 PWM at zero brightness:


    Amazing. Could you test some of the newer iphones, in case they give you eyestrain as well? Im gonna do that on my work iphone where I have absolutely terrible and long lasting pain.

    Yes the software looks crap compared to Zeitnitz. Also we might need to get a better photodiode just to be sure. I was recommended this - https://www.conrad.cz/pin-fotodioda-osram-components-bpx-61-to-39-vyz-uhel-55-400-1100-nm.k153122

    @Wootever please what is the difference when you use the diode with the circuit as bought from ebay?

      martin
      The transimpedance amplifier converts current from the photodiode to a voltage usable by the oscilloscope (it basically amplify the signal for a more stable output).

      The advantage of a combined/embedded design:
      The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs, such as leakage current errors, noise pick-up, and gain peaking as a result of stray capacitance.

          Wootever Thank you, that is amazing. And it can be clipped to the oscope probes like the regular diode? Could you show a photo of how it is attached to the oscope so it works? I will order it from your link.

              Wootever Thank you, so I just connect the probe tip to the middle two, probe ground to the bottom two and it will work? What about the voltage supply? (Red)

                  martin
                  Voltage supply is needed for the transimpedance amplifier, but the power consumption is very low, a single 9V battery probably lasts for months/years.

                  Edit:
                  Here are a few example photos of a basic OPT101 photosensor:

                  Galaxy S8 AMOLED PWM on 10cd/m2:

                      Wootever Thank you, that is exactly what I needed. Im on to get better readings then🙂

                        9 days later

                        For Android there's an app called "HScope". It supports various Hantek devices, including the 6022BE. My first impression is that it's great software. It detects frequencies much better than OpenHantek does and generally seems very polished. We might be able to create a portable solution with an Android device, a USB On-The-Go cable, a power bank, 6022BE + probe, and the HScope app.

                        HScope App: https://play.google.com/store/apps/details?id=com.martinloren.hscope
                        Guide: http://hscope.martinloren.com

                        • JTL replied to this.

                          KM Very cool. How much does said Hantek oscilloscope cost?

                          • KM replied to this.

                              JTL $63.49 @amazon.com

                              • JTL replied to this.

                                  KM Not bad. Do you know the highest frequency/sample rate it can capture?

                                  • KM replied to this.
                                      5 days later

                                      KM Does the sample rate matter much? I read hantek 6022be range is 20Mhz, will it therefore display properly any PWM that might be in that range, like new macbooks 100khz?

                                      • KM replied to this.

                                          martin I'm not sure. I hope so. I didn't encounter any high speed PWM yet.

                                              KM What was the highest freq you measured with it? Mine was 20khz with the soundcard, but the actual graph seems off, so not sure.

                                              • KM replied to this.
                                                  14 days later

                                                  martin No more than 240 Hz yet. I find the soundcard solution to be much more responsive. It even picks up my ceiling's 100 Hz incandescent flicker from afar while the Hantek oscilloscope receives a flat line. Maybe the photodiode needs an additional external voltage. The audio cable somehow might supply that voltage.

                                                    2 months later

                                                    martin my setup is enclosed in a case so it's not easy to photograph. I started off with a cheap Amazon USB scope but found that I was hitting the limits pretty easily. My present scope was rather expensive and does an actual 500 MS/s so it won't ever be the weak link.

                                                    The special sauce is having a really clean power source and then adding a 100,000 ohm (or higher) resistor to amplify the fluctuations coming out of the diode. Also, be certain that the diode's switching rate is sufficiently fast to capture the frequency you're looking for.

                                                      7 days later
                                                      dev