Lope Posted June 20, 2018 Posted June 20, 2018 Since some H2 and H3's run hotter than some people would like, and people are measuring voltages etc I thought I'd make the following warnings for your benefit in the hope that we collect quality data and solve all challenges quickly.Measuring voltage accurately Your DMM (digital multimeter) may lie to you. Measure the input voltage as well as the test voltages before posting voltage readings. Check with the resistance setting that the resistance of your probes touching each other is close to 0 ohms. I own many DMM's and one of them reports horribly inaccurate voltages when the 9v battery is near or less than 8v. If your DMM sucks, buy a better one (link at bottom)TL;DR Step 1. Check probes shorted is close to 0 ohms Step 2. Test and report 5v input voltage Step 3. Test and report whatever voltage is of interest to you.You need 3 DMM's to verify accuracy, from time to time You need to own 3 DMM's (preferably different brands/models) then you measure a voltage with all 3 meters to see if they agree. (or own 1 DMM and borrow 2 for the test)If you use 1 DMM: You cannot trust what it tells you.If you use 2 DMM's: You only know if you have a problem. If they disagree, you don't know which is right and which is wrong.If you use 3 DMM's: The 3rd DMM will arbitrate a discrepancy. Every few months or years you should repeat this test. A DMM's accuracy may depend on it's batteries being very fresh or it may corrode inside. Verify to trust.Measuring temperature accurately Temperature reported by some boards onboard sensors are horribly inaccurate. Do not believe these numbers. (eg: Orange Pi Zero) - For good temperature measurements, buy yourself some cheap and nice equipment.IR thermometer (note, the laser doesn't point in the exact same place as the IR sensor at all distances, best to turn the laser off, it's a gimmick, temperature sensing is only accurate when measuring matte dark coloured surfaces, it won't work well on shiny/bright coloured surfaces, to hack, add some black insulation tape or better: colour in with black permanent marker)DS18B20 1wire accurate digital thermometer IC's (there are lots of tutorials for hooking these up to RbPi etc, hopefully someone (maybe me) can do it for an Orange Pi etc and post pics/schematic/code)Digital LCD Temperature Probe (not an ideal probe shape probably, but very easy to use, this one's temp range goes up to 110C, some only go to 70C)Good quality DMM with temperature probe (reviewed by EEVlog) USB Doctor (with individual voltage and current in different colours is MUCH easier to use than the cheap crappy single display monochrome ones. Some of these claim a range of 3-9v and 3A. So it could technically be used on the 3.3v rail but you should confirm it's accuracy at different currents and voltages with a good DMM)USB Doctor 3-7.5V, 0-2.5AUSB Doctor 3-8V, 0-3AUSB Doctor 3-9V, 0-5AFancy USB Doctor, 4-30V 0-5A shows power, time and mAh Measure current and voltage (calculate power) accurately Ammeters (digital or analog) have significant resistance and will cause a voltage drop. If you use one, measure voltage at the target device power inputs (after the ammeter). (if you use a USB Doctor for example, it's the same as using 2 DMM's, one for current, one for voltage) None of these links contain any affiliate references, I just searched eBay and chose good examples and I've bought the above DMM myself, buy whatever you want, I just want you to have good quality instruments and report accurate data.
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