00:00:00.050 hi this should be an interesting little 00:00:02.48000:00:02.490 video it involves my new eevblog BM 235 00:00:05.88900:00:05.899 multimeter and this is something I 00:00:08.27000:00:08.280 didn't realize but people who have 00:00:10.73000:00:10.740 bought this a couple of reports started 00:00:13.73000:00:13.740 to flow in that it actually produces a 00:00:15.98000:00:15.990 high pitch whine when you turn the 00:00:20.17900:00:20.189 backlight on like that there's a very 00:00:21.89000:00:21.900 faint if you put your ear like some 00:00:24.05000:00:24.060 people can like hear it from you know 00:00:26.08900:00:26.099 like a standing distance away other 00:00:27.92000:00:27.930 people have to like put it right up to 00:00:30.23000:00:30.240 their ear to hear the thing but it's 00:00:32.17900:00:32.189 producing a high-pitched tone now I 00:00:35.06000:00:35.070 didn't actually notice this when I 00:00:36.91000:00:36.920 evaluated the original unit and ordered 00:00:40.52000:00:40.530 these things but sure enough it is on 00:00:43.76000:00:43.770 the original one as well but I've got to 00:00:46.34000:00:46.350 hold this transmitted right up to my ear 00:00:49.01000:00:49.020 to sort of do that so they see and I've 00:00:51.68000:00:51.690 tested various um I had like you know it 00:00:54.41000:00:54.420 still had twenty or something here and I 00:00:56.77900:00:56.789 tested various ones and this seems to be 00:00:58.84900:00:58.859 quite a significant difference between 00:01:01.06900:01:01.079 units some are louder than others and 00:01:03.56000:01:03.570 there seems to be a slightly different 00:01:05.57000:01:05.580 frequency between 00:01:07.37000:01:07.380 units as well so I thought we'd just do 00:01:10.25000:01:10.260 an investigation but it's already been 00:01:12.23000:01:12.240 done that by some forum members and 00:01:15.74000:01:15.750 people on the eevblog IRC channel yes 00:01:19.16000:01:19.170 there is such a thing apparently there's 00:01:20.84000:01:20.850 people who hang out on the eevblog IRC 00:01:23.09000:01:23.100 channel and they discovered the problem 00:01:26.84000:01:26.850 in this thing and so we do know the 00:01:29.42000:01:29.430 solution but hey I thought we'd just 00:01:31.06900:01:31.079 take a look at it because it's 00:01:32.45000:01:32.460 interesting and it's something I've 00:01:33.83000:01:33.840 mentioned way back in episode number 33 00:01:37.99900:01:38.009 part 2 back when the YouTube had 00:01:40.37000:01:40.380 10-minute time limits have to do two 00:01:42.20000:01:42.210 parts hmm now I'll do my best to try and 00:01:45.13900:01:45.149 get this sound on the microphone here 00:01:47.89900:01:47.909 it's incredibly difficult I've tried 00:01:49.31000:01:49.320 different microphones and things like 00:01:50.69000:01:50.700 that 00:01:51.02000:01:51.030 but I'll give it a bash here we go 00:01:53.70000:01:53.710 and that if I speak very softly in a 00:01:57.99000:01:58.000 whisper I've got my game turned all the 00:02:01.11000:02:01.120 way up and maybe you can hear it Shh so 00:02:07.65000:02:07.660 that's the back line on and I'll turn it 00:02:10.08000:02:10.090 off 00:02:14.39000:02:14.400 that's now often should be gone and back 00:02:17.58000:02:17.590 on 00:02:21.37000:02:21.380 so there you have it you clearly heard 00:02:23.96000:02:23.970 that tone there it's around about five 00:02:26.00000:02:26.010 kilohertz or so and it's clearly coming 00:02:28.76000:02:28.770 on when you turn the backlight on it 00:02:30.89000:02:30.900 otherwise it's a completely silent so 00:02:33.11000:02:33.120 it's something to do with the backlight 00:02:34.85000:02:34.860 inverter circuit that's actually driving 00:02:37.25000:02:37.260 the LEDs in here because this thing is 00:02:40.22000:02:40.230 only powered from two double-a batteries 00:02:44.54000:02:44.550 right so they're 1.5 volts maximum at 3 00:02:47.03000:02:47.040 volts maximum so the white LEDs in here 00:02:49.16000:02:49.170 obviously need at least that to work so 00:02:52.19000:02:52.200 when the batteries drop in haven't got 00:02:53.93000:02:53.940 enough voltage so there needs to be some 00:02:56.24000:02:56.250 sort of boost converter in here to 00:02:59.09000:02:59.100 actually drive these LEDs and that's 00:03:01.07000:03:01.080 what the problem is so I won't leave you 00:03:03.77000:03:03.780 hanging yes it is the backlight that 00:03:05.81000:03:05.820 circuitry in here but if we have a look 00:03:08.93000:03:08.940 at inside this thing then when you hear 00:03:12.17000:03:12.180 something like this there are three 00:03:14.08000:03:14.090 typical reasons why you would hear some 00:03:17.72000:03:17.730 sort of wine or tone coming from an 00:03:20.63000:03:20.640 instrument but all of them involve some 00:03:23.24000:03:23.250 sort of electromechanical process that 00:03:27.19900:03:27.209 you know generate into vibe something 00:03:29.24000:03:29.250 needs to vibrate to generate the sound 00:03:31.64000:03:31.650 the audible sound that you're hearing 00:03:33.68000:03:33.690 and of course the prime culprit might be 00:03:36.25900:03:36.269 look we have a little piezo ceramic 00:03:39.25900:03:39.269 buzzer inside this thing it's designed 00:03:41.75000:03:41.760 to generate sound is that that perhaps 00:03:43.91000:03:43.920 so you'd naturally think of that but 00:03:46.49000:03:46.500 that's fairly easy to rule out now the 00:03:49.55000:03:49.560 second one is in inductors inductors can 00:03:53.60000:03:53.610 actually their coils of wire and at the 00:03:57.11000:03:57.120 right frequency they can actually 00:03:59.05000:03:59.060 vibrate and do things like that well the 00:04:01.25000:04:01.260 only inductor in here is this puppy on 00:04:04.91000:04:04.920 the bottom but in and he looks like oh 00:04:07.31000:04:07.320 look here's the backlight the springs 00:04:10.25000:04:10.260 for the backlight down here here's the 00:04:11.87000:04:11.880 backlight board with the LEDs on it down 00:04:14.63000:04:14.640 here and you might think oh it's going 00:04:16.84900:04:16.859 over to the inductor but if you actually 00:04:18.11000:04:18.120 follow the traces it's not I believe 00:04:20.12000:04:20.130 that inductor I don't have the schematic 00:04:21.86000:04:21.870 for this but I believe the inductor is 00:04:23.81000:04:23.820 actually part of the electric field 00:04:26.33000:04:26.340 detection circuit so it's got nothing to 00:04:29.81000:04:29.820 do with the backlight at all now another 00:04:32.60000:04:32.610 common one is that trance 00:04:34.32000:04:34.330 formers of course they've got 00:04:35.51000:04:35.520 laminations of material in there and if 00:04:38.24900:04:38.259 they're not very tightly mechanically 00:04:41.46000:04:41.470 bound they can actually vibrate you may 00:04:43.29000:04:43.300 have heard that classic you know 50 60 00:04:45.74900:04:45.759 Hertz transformer hum coming from an 00:04:49.14000:04:49.150 instrument well it's clearly not that we 00:04:50.90900:04:50.919 don't have any transformers in here 00:04:52.92000:04:52.930 they're not whining you know especially 00:04:55.08000:04:55.090 like a switch mode DC to DC transformer 00:04:58.08000:04:58.090 which operates at higher frequencies 00:05:00.02900:05:00.039 which can be in the audible range by the 00:05:02.58000:05:02.590 way if there are you know that lower 00:05:05.55000:05:05.560 frequency usually DC these converters 00:05:07.52900:05:07.539 are a higher you know frequency in the 00:05:10.35000:05:10.360 you know in the non audible range ia 00:05:12.30000:05:12.310 greater than 20 kilohertz you know maybe 00:05:14.55000:05:14.560 a couple of hundred kilohertz even in 00:05:16.26000:05:16.270 the megahertz range so generally you're 00:05:18.80900:05:18.819 not going to get them from DC to DC 00:05:20.10000:05:20.110 converters although I have heard them 00:05:22.11000:05:22.120 happening some that operate down in the 00:05:24.18000:05:24.190 audible range reductions you can see 00:05:25.83000:05:25.840 there's no traditional DC to DC 00:05:27.36000:05:27.370 converter in here 00:05:28.49900:05:28.509 no I transform anything like that so 00:05:31.74000:05:31.750 it's not that so the last remaining one 00:05:34.23000:05:34.240 you have to actually go back to our 00:05:35.73000:05:35.740 episode number 33 part 2 as I mentioned 00:05:38.96900:05:38.979 that before way back in the old lab when 00:05:41.18900:05:41.199 I did a tutorial on capacitors and I 00:05:44.45900:05:44.469 mentioned ceramic capacitors and in 00:05:46.55900:05:46.569 particular multi-layer ceramic 00:05:48.60000:05:48.610 capacitors as you've no doubt you know 00:05:50.73000:05:50.740 little oh six oh three ceramic 00:05:52.82900:05:52.839 capacitors and stuff like that that you 00:05:54.54000:05:54.550 typically see in all modern electronics 00:05:56.70000:05:56.710 well these can actually be microphonic 00:05:59.82000:05:59.830 they can actually pick up sounds so if 00:06:02.96900:06:02.979 you're why I'm talking now and trust me 00:06:05.45900:06:05.469 these little multi-layer ceramic 00:06:06.77900:06:06.789 capacitors in here will actually be 00:06:09.39000:06:09.400 picking up that sound and due to micro 00:06:13.14000:06:13.150 phonics they will actually be generating 00:06:16.37900:06:16.389 and my new it might be micro volts but 00:06:18.11900:06:18.129 they'll be generating minut voltages 00:06:19.95000:06:19.960 across the capacitor and that comes 00:06:22.64900:06:22.659 about because of the name of the things 00:06:24.48000:06:24.490 it's a dead giveaway multi-layer ceramic 00:06:26.85000:06:26.860 capacitors and they're constructed using 00:06:29.73000:06:29.740 as a name implies multiple layers in 00:06:33.51000:06:33.520 there and there are ceramics so they 00:06:36.45000:06:36.460 actually become piezo ceramic 00:06:38.62900:06:38.639 transducers just like this little puppy 00:06:41.67000:06:41.680 up here just like those transducers you 00:06:44.30900:06:44.319 used to in also you seen all sorts of 00:06:46.62000:06:46.630 products those little flat 00:06:48.63000:06:48.640 piezo ceramic transducers exactly the 00:06:51.06000:06:51.070 same things going on except you've got 00:06:52.71000:06:52.720 multiple layers inside these multi-layer 00:06:55.68000:06:55.690 ceramic capacitors so not only are they 00:06:58.98000:06:58.990 microphonic and they can pick up sounds 00:07:00.78000:07:00.790 it works in the reverse as well they 00:07:03.14000:07:03.150 actually exhibit the piezoelectric 00:07:05.88000:07:05.890 effect just like a piezo ceramic 00:07:08.79000:07:08.800 transducer up here if you apply a 00:07:10.59000:07:10.600 voltage to them an AC voltage in the 00:07:12.90000:07:12.910 audible range they may actually vibrate 00:07:16.83000:07:16.840 and emit a tone and the PCB can actually 00:07:20.34000:07:20.350 help amplify that and other stuff but 00:07:22.46000:07:22.470 yeah these things can actually be little 00:07:26.16000:07:26.170 tiny capacitors in here can generate 00:07:28.85000:07:28.860 sound amazing 00:07:31.44000:07:31.450 so given that this our buzzer is under a 00:07:34.77000:07:34.780 software control comes directly from one 00:07:37.26000:07:37.270 of the pins and I don't think it's that 00:07:39.27000:07:39.280 given that we don't have any inductors 00:07:41.70000:07:41.710 in there in the circuit I don't think 00:07:44.04000:07:44.050 it's that we haven't got any 00:07:45.27000:07:45.280 transformers in there now it's not that 00:07:47.52000:07:47.530 what's left 00:07:48.39000:07:48.400 these multi-layer ceramic capacitors 00:07:50.94000:07:50.950 bingo let's go to the datasheet 00:07:53.34000:07:53.350 as you should have done first and you 00:07:55.95000:07:55.960 could have would have been probably 00:07:57.54000:07:57.550 obvious what the culprit was so here we 00:08:01.11000:08:01.120 are at the datasheet the hy 26 1 3 C is 00:08:04.59000:08:04.600 the one we have and bingo right here it 00:08:07.14000:08:07.150 tells you built-in charge pump a LED 00:08:09.84000:08:09.850 backlight built-in charge pump so if we 00:08:12.33000:08:12.340 go down we should be able to find this I 00:08:14.58000:08:14.590 hope you can read your Chinese but yeah 00:08:18.65000:08:18.660 internal we can't see it is there a 00:08:21.51000:08:21.520 charge pump in there somewhere there's 00:08:23.10000:08:23.110 got to be it'll show you somewhere 00:08:25.05000:08:25.060 anyway if we keep going all the way with 00:08:27.78000:08:27.790 LBJ down here then wait for it wait for 00:08:33.81000:08:33.820 it wait for it all timing diagrams 00:08:38.31000:08:38.320 fantastic bingo here it is there's our 00:08:41.07000:08:41.080 lead driver charge pup engines your 00:08:43.65000:08:43.660 typical capacitor charge pump and you 00:08:46.02000:08:46.030 can see that it's actually got a current 00:08:47.61000:08:47.620 sense resistor down here so it can 00:08:50.31000:08:50.320 actually control the current going 00:08:52.53000:08:52.540 through the LED so it's going to be a 00:08:53.76000:08:53.770 constant current generator operating at 00:08:55.98000:08:55.990 some frequency that frequency we don't 00:08:58.41000:08:58.420 know it's not in the datasheet at all at 00:09:01.23000:09:01.240 least 00:09:01.89000:09:01.900 well if you can't read Chinese there it 00:09:04.26000:09:04.270 is is it 15 milliamps is that the 00:09:06.82900:09:06.839 maximum obviously it's going to probably 00:09:09.57000:09:09.580 the maximum it's going to depend on the 00:09:11.34000:09:11.350 resistor value down here but we can see 00:09:13.59000:09:13.600 that we have this 10 micro farad well 00:09:16.01900:09:16.029 assuming that they've followed the 00:09:17.85000:09:17.860 application note here there's going to 00:09:19.86000:09:19.870 be a 10 micro farad output smoothing cap 00:09:22.32000:09:22.330 and there's going to be a 1 micro farad 00:09:24.26900:09:24.279 charge pump cap in here so there it is 00:09:27.69000:09:27.700 there's the culprit right there see 44 00:09:31.44000:09:31.450 10 micro farad multi-layer ceramic 00:09:33.84000:09:33.850 capacitor and it's probably one of those 00:09:35.43000:09:35.440 dodgy you know why 5u dielectric 00:09:38.25000:09:38.260 material or something like that you know 00:09:39.90000:09:39.910 the ones that are really horrible have 00:09:42.12000:09:42.130 really horrible thermal and electrical 00:09:44.18000:09:44.190 characteristics but they're great for 00:09:45.96000:09:45.970 bypassing applications and you know 00:09:48.12000:09:48.130 stuff like that they're just fine for it 00:09:50.01000:09:50.020 but they're a horrible dielectric and 00:09:52.26000:09:52.270 they can in theory be more susceptible 00:09:55.41000:09:55.420 to this sort of problem and by the way 00:09:57.39000:09:57.400 this problem only happens to what class 00:10:00.00000:10:00.010 2 ceramics I don't believe there's a 00:10:02.55000:10:02.560 single case of it ever happening with 00:10:04.11000:10:04.120 class 1 NPO type ceramics those zero 00:10:08.61000:10:08.620 temperature coefficient ones that are 00:10:10.89000:10:10.900 much lower value so what we want to do 00:10:14.01000:10:14.020 is actually get in here and prove this 00:10:16.80000:10:16.810 thing and see what happens see if we can 00:10:18.42000:10:18.430 measure some stuff on here but as you 00:10:20.67000:10:20.680 can see the battery compartment has 00:10:23.16000:10:23.170 these two Springs here and they contact 00:10:25.76900:10:25.779 these little pads down here and it's 00:10:27.36000:10:27.370 really annoying I'd have to like solder 00:10:30.26900:10:30.279 some you know contacts on there because 00:10:32.25000:10:32.260 if I put the go put the board back in 00:10:33.84000:10:33.850 where we can't probe anything can we 00:10:36.12000:10:36.130 it's really annoying maybe like I could 00:10:37.82900:10:37.839 solder some wires on and then bring it 00:10:39.93000:10:39.940 back out for example and then screw the 00:10:42.51000:10:42.520 board back in and bring it back out 00:10:43.82900:10:43.839 that's one way to do it and another way 00:10:45.93000:10:45.940 to do it which is what some of the guys 00:10:47.22000:10:47.230 on the forum have done is just 00:10:48.87000:10:48.880 physically remove the screen like that 00:10:50.91000:10:50.920 whack the board back in and back in 00:10:53.97000:10:53.980 there we go and then you can access and 00:10:56.67000:10:56.680 probe stuff through the front here but 00:10:58.98000:10:58.990 of course we're disconnecting the load 00:11:00.96000:11:00.970 from this puppy we're disconnecting the 00:11:02.79000:11:02.800 led so I think I'll do it the other way 00:11:04.86000:11:04.870 I'll put the screen back in Oh solder 00:11:07.71000:11:07.720 some wires on to some various places and 00:11:10.23000:11:10.240 then we can not bring that back out all 00:11:12.18000:11:12.190 right what I've done the solder for 00:11:13.50000:11:13.510 little wires on here we've got 00:11:15.39000:11:15.400 and and the our main output 10 00:11:18.36000:11:18.370 microfarad filter cap which is the 00:11:20.31000:11:20.320 culprit here and then we've got the a 00:11:23.64000:11:23.650 charge pump capacitor so both wires 00:11:26.01000:11:26.020 coming out there I've just been time 00:11:27.69000:11:27.700 around like that I could actually try 00:11:30.15000:11:30.160 and bring it out the optional led hole 00:11:32.73000:11:32.740 here um optional it's not an option on 00:11:35.25000:11:35.260 this model but there's actually 00:11:36.30000:11:36.310 curiously there's a footprint down there 00:11:38.43000:11:38.440 so maybe I should install an LED on 00:11:40.32000:11:40.330 there and see if it uh you know see if 00:11:43.59000:11:43.600 it does anything anyway uh maybe we can 00:11:45.81000:11:45.820 probe that mm-hmm anyway I'm going to 00:11:48.66000:11:48.670 set that on there and it is a little bit 00:11:51.33000:11:51.340 tricky and we can actually get 00:11:54.44000:11:54.450 eventually get contact and pair it up 00:11:58.07000:11:58.080 beauty and here we go I'm probing 00:12:00.87000:12:00.880 directly across the 10 microfarad output 00:12:03.75000:12:03.760 capacitor that c-44 that's the output 00:12:06.48000:12:06.490 field of capacitor it's a constant 00:12:08.34000:12:08.350 current drive boosted constant current 00:12:10.95000:12:10.960 drive and I've got it set to our DC 00:12:12.89000:12:12.900 coupling here and my ground points right 00:12:15.96000:12:15.970 down there 500 millivolts per division 00:12:17.52000:12:17.530 so 1 volt 2 volts 3 volts there we go so 00:12:20.76000:12:20.770 it's around about the 3 volt level but 00:12:22.41000:12:22.420 we can AC couple that and bring that 00:12:25.77000:12:25.780 back up here bingo now if we have a look 00:12:29.01000:12:29.020 at the signal here you'll notice that 00:12:31.23000:12:31.240 not only does it have this interesting 00:12:32.91000:12:32.920 looking little bump in there like that 00:12:36.03000:12:36.040 ok 00:12:37.02000:12:37.030 but it's jumping around like a 00:12:39.06000:12:39.070 jackrabbit okay and if we stop it you'll 00:12:42.96000:12:42.970 notice that there's look there is 00:12:45.60000:12:45.610 another period inside there it's sort of 00:12:48.18000:12:48.190 oscillating like that as well and you 00:12:50.85000:12:50.860 also notice it's not a fixed frequency 00:12:53.55000:12:53.560 either you can actually see the 00:12:55.89000:12:55.900 difference between there that peak and 00:12:57.30000:12:57.310 that peak is shorter than the time 00:12:59.28000:12:59.290 period between that one and that one and 00:13:01.26000:13:01.270 you can actually hear this um sorry I 00:13:04.29000:13:04.300 can't mix it directly with the well 00:13:06.36000:13:06.370 actually I probably can mix it with the 00:13:08.67000:13:08.680 microphone hmm but you can see it jumps 00:13:12.45000:13:12.460 between you saw ah there we go almost 00:13:14.82000:13:14.830 perfect right it jumps between periods 00:13:16.95000:13:16.960 of almost perfect and this is touch 00:13:19.65000:13:19.660 sensitive try I was getting it before 00:13:21.68000:13:21.690 trust me now it's not cooperating the 00:13:24.21000:13:24.220 white coat syndrome but you can 00:13:28.74000:13:28.750 I can actually get it where it is almost 00:13:30.69000:13:30.700 a perfect tone okay and you can actually 00:13:33.93000:13:33.940 hear it as well I'll try and mix in the 00:13:36.36000:13:36.370 audio in a second if I can get this damn 00:13:37.89000:13:37.900 thing to cooperate but it is sensitive 00:13:40.62000:13:40.630 to think all sorts of Anakin what there 00:13:43.92000:13:43.930 it is there it is bang you saw it right 00:13:46.08000:13:46.090 it was almost perfect and if you got 00:13:47.76000:13:47.770 your ear up to it you can actually hear 00:13:49.17000:13:49.180 a perfect time okay I'm whispering again 00:13:52.29000:13:52.300 hopefully you can hear this I'm trying 00:13:54.84000:13:54.850 to mix in the audio I'm using my 00:13:57.06000:13:57.070 external wireless mic and I've really 00:13:59.13000:13:59.140 got to turn the gain right up here we go 00:14:01.56000:14:01.570 that's perfect time and hopefully you 00:14:04.38000:14:04.390 can hear it glitching so as you can see 00:14:15.99000:14:16.000 it's jumping around like a jackrabbit 00:14:18.27000:14:18.280 there I had that smoothing mode on 00:14:20.52000:14:20.530 before by the way I've just turned it to 00:14:22.31000:14:22.320 refresh update mode so yeah that charge 00:14:25.29000:14:25.300 pump um seems to be jumping around like 00:14:27.84000:14:27.850 a jackrabbit like it's got some sort of 00:14:30.60000:14:30.610 maybe pulse skipping mode or something 00:14:33.45000:14:33.460 like that in it so yeah it's you know 00:14:36.69000:14:36.700 not a pure tone at all and it just it 00:14:39.96000:14:39.970 varies like all the time just like 00:14:42.81000:14:42.820 sitting like randomly and tense seems to 00:14:45.15000:14:45.160 also very like just sitting there it'll 00:14:47.55000:14:47.560 vary and it also seems to vary when I 00:14:49.73000:14:49.740 physically touch and you know play 00:14:52.82900:14:52.839 around with the unit as well and if we 00:14:54.72000:14:54.730 have a look at the frequency of this 00:14:56.01000:14:56.020 thing um you know the frequency counter 00:14:58.50000:14:58.510 up here I don't know what it's detecting 00:15:00.45000:15:00.460 it anyway it's still updating because 00:15:01.82900:15:01.839 it's a hardware out frequency counter in 00:15:03.72000:15:03.730 the background but I've got my cursors 00:15:05.37000:15:05.380 here and you can see delta T here is a 00:15:09.59000:15:09.600 3.86 kilohertz there we go and if we 00:15:13.29000:15:13.300 turn the cursor over to that shorter 00:15:16.11000:15:16.120 period there we're looking at five point 00:15:19.26000:15:19.270 one two so it's going to you know vary 00:15:21.21000:15:21.220 and jump between those two frequencies 00:15:23.55000:15:23.560 that's why it often sounds very muddied 00:15:26.94000:15:26.950 it's not a pure tone at all and if we 00:15:29.19000:15:29.200 have a look at the waveform on one side 00:15:30.72000:15:30.730 of the charge pump capacitor you can see 00:15:33.36000:15:33.370 that or you can see it's switching where 00:15:36.03000:15:36.040 it actually switches on here so yeah 00:15:38.40000:15:38.410 that's you know it's doing yeah 00:15:42.42000:15:42.430 it's pretty consistent there actually 00:15:44.63900:15:44.649 but as I said it varies and the chain in 00:15:47.57900:15:47.589 the tone changes when I actually 00:15:49.97000:15:49.980 disconnect the probe so see if we can 00:15:53.01000:15:53.020 see a change up here when I disconnect 00:15:54.42000:15:54.430 this yep 00:15:56.46000:15:56.470 see I changed it the capacitance of the 00:15:59.40000:15:59.410 probe and there's the other line there 00:16:01.53000:16:01.540 not a huge amount of difference but you 00:16:03.63000:16:03.640 can certainly see if I disconnect that 00:16:05.69900:16:05.709 probe I will upset that there we go 00:16:08.25000:16:08.260 upset the applecart ah doesn't like it 00:16:11.79000:16:11.800 but it's actually more stable when I 00:16:14.43000:16:14.440 actually load it down with the probe I'm 00:16:16.29000:16:16.300 using the x one probe here I'm not using 00:16:18.51000:16:18.520 x 10 if I switch at the x 10 then it's 00:16:21.90000:16:21.910 still loaded it down somewhat there we 00:16:25.62000:16:25.630 go and check out the high frequency 00:16:27.75000:16:27.760 ringing on that look at that we and if 00:16:32.51900:16:32.529 we go over here we'll see it here as 00:16:34.05000:16:34.060 well love it you that beautiful okay 00:16:39.32900:16:39.339 everyone wants to see the money shot 00:16:41.13000:16:41.140 which is the microphones I've got my 00:16:42.96000:16:42.970 wireless mic the output here I've got 00:16:45.42000:16:45.430 like max gain so you know it's going to 00:16:47.82000:16:47.830 be pretty horrible channel to the blue 00:16:49.65000:16:49.660 waveform here is obviously my voice 00:16:52.01900:16:52.029 check it out 00:16:53.31000:16:53.320 there we go that's my voice and I 00:16:55.19900:16:55.209 haven't turned the backlight on so we'll 00:16:57.24000:16:57.250 turn the backlight on but this is the 00:16:58.65000:16:58.660 background level okay so let me show you 00:17:01.14000:17:01.150 that bingo 00:17:09.41900:17:09.429 correlation time now at first it may 00:17:11.85000:17:11.860 just look like crap right and it doesn't 00:17:14.04000:17:14.050 correlate at all I mean look this peak 00:17:16.23000:17:16.240 here doesn't line up with this one but 00:17:18.24000:17:18.250 uh-huh watch this this is the acoustic 00:17:21.21000:17:21.220 delay if you shift this over to here and 00:17:24.03000:17:24.040 you shift this one over by the same 00:17:27.00000:17:27.010 amount they line up so have just got 00:17:30.24000:17:30.250 some delay there that's all tiny a 00:17:32.94000:17:32.950 little bit of delay but it basically 00:17:34.70000:17:34.710 this here correlates with this here this 00:17:38.88000:17:38.890 one correlates with that and so on this 00:17:41.61000:17:41.620 one correlates with that bingo so it's 00:17:44.49000:17:44.500 really difficult to actually pick this 00:17:46.50000:17:46.510 up I'm sorry about that but we can at 00:17:49.14000:17:49.150 least see the correlation there and of 00:17:50.79000:17:50.800 course if I switch the backlight off 00:17:52.16900:17:52.179 here we go 00:17:56.96000:17:56.970 there we go we've just got the 00:17:59.85000:17:59.860 background and you can see that there's 00:18:02.16000:18:02.170 no high-frequency stuff on there at all 00:18:03.87000:18:03.880 ah this is better I've increased the 00:18:06.36000:18:06.370 output gain on the microphone here and 00:18:08.70000:18:08.710 this is what I'm getting here we go this 00:18:11.58000:18:11.590 is much better and you can have a look 00:18:14.01000:18:14.020 at see those Peaks look at that those 00:18:17.49000:18:17.500 bottom Peaks precisely correlate with a 00:18:21.27000:18:21.280 fixed amount of delay the delay is the 00:18:23.88000:18:23.890 acoustic delay so um look I mean there's 00:18:27.99000:18:28.000 you know it's not an exact match for the 00:18:31.35000:18:31.360 for the voltage waveform on the 00:18:33.54000:18:33.550 capacitor but this has to do with 00:18:35.64000:18:35.650 although piezo ceramic nature of the 00:18:38.28000:18:38.290 thing and how it actually produces sound 00:18:40.11000:18:40.120 but as you can see the frequency 00:18:41.78000:18:41.790 correlates and that is what matters 00:18:44.73000:18:44.740 that's what's producing the sound there 00:18:47.10000:18:47.110 so that pain in the arse 10 microfarad 00:18:49.56000:18:49.570 multi-layer ceramic capacitor gotcha and 00:18:53.04000:18:53.050 if I start that again and then turn off 00:18:56.67000:18:56.680 the back light that's a normal 00:19:04.56000:19:04.570 background it's just picking up the 00:19:06.03000:19:06.040 regular background hum and other crap 00:19:09.36000:19:09.370 here in the lab but none of that 5 00:19:11.61000:19:11.620 kilohertz frequency content so that's 00:19:14.40000:19:14.410 all very interesting but what is the fix 00:19:16.65000:19:16.660 for this thing well the fix is to change 00:19:20.40000:19:20.410 that capacitor now this could have 00:19:22.77000:19:22.780 happened between our various batches as 00:19:25.38000:19:25.390 well depending on what 10 microfarad cap 00:19:28.44000:19:28.450 if they didn't specifically specify in 00:19:30.90000:19:30.910 manufacturing in the Bill of Materials a 00:19:32.79000:19:32.800 specific part number and model of 00:19:35.07000:19:35.080 capacitor always from the same 00:19:36.78000:19:36.790 manufacturer which is you know not all 00:19:39.87000:19:39.880 that untypical arm when you're just 00:19:42.00000:19:42.010 talking about a Joe Bloggs 10 micro 00:19:44.34000:19:44.350 farad bypass cap like this you may think 00:19:46.71000:19:46.720 well you know what's the big deal it's a 00:19:48.75000:19:48.760 10 it's value doesn't exactly matter you 00:19:51.39000:19:51.400 know it can be half that it can be 00:19:52.74000:19:52.750 double it you know it's not a huge big 00:19:55.02000:19:55.030 deal it's just for a backlight here so 00:19:57.36000:19:57.370 there you know wouldn't surprise me if 00:19:59.43000:19:59.440 they haven't specified that so the 00:20:01.59000:20:01.600 purchasing people can just go and chew 00:20:04.20000:20:04.210 you know I'm pretty much free to choose 00:20:06.15000:20:06.160 if it's not specified free to choose any 00:20:08.34000:20:08.350 capacitor they can get from anywhere as 00:20:10.13900:20:10.149 long as it's you know exactly the same 00:20:11.73000:20:11.740 size the same voltage rating it's 10 00:20:13.95000:20:13.960 microfarads blah blah blah but this is a 00:20:15.89900:20:15.909 problem that is most definitely going to 00:20:18.04900:20:18.059 vary between manufacture of capacitor 00:20:20.97000:20:20.980 between model between dielectric between 00:20:22.98000:20:22.990 different sub physical sizes be at Oh 00:20:25.35000:20:25.360 603 oh la 5 1206 etc what sort of our 00:20:30.24000:20:30.250 current that we're actually what it's 00:20:32.12900:20:32.139 filtering things like that it's kind of 00:20:34.35000:20:34.360 very a lot so how can we fix this thing 00:20:37.23000:20:37.240 well we can simply try and change the 00:20:40.01900:20:40.029 cap either to our another 10 micro farad 00:20:42.86900:20:42.879 but it's a different brand different 00:20:44.46000:20:44.470 dielectric whatever I don't know I'll 00:20:46.35000:20:46.360 just find one i've got lying around here 00:20:48.06000:20:48.070 replace it see if it goes away and 00:20:50.27900:20:50.289 here's the first 10 micro farad cap i 00:20:52.11000:20:52.120 found lying around 25 volts it's an x5 00:20:54.86900:20:54.879 our dielectrics and on this y5 you 00:20:57.48000:20:57.490 rubbish or anything like that but i 00:20:58.79900:20:58.809 don't know what is actually inside this 00:21:01.68000:21:01.690 thing and yes the x5 ours you know your 00:21:05.11900:21:05.129 x7 ours they can have exactly the same 00:21:08.38900:21:08.399 piezoelectric effect as well so anyway i 00:21:11.75900:21:11.769 like what are these in and see what 00:21:13.23000:21:13.240 happens and here's a close-up shot of 00:21:15.09000:21:15.100 the cap I took out there just D soldered 00:21:17.54900:21:17.559 that puppy look for 10 microfarads that 00:21:20.10000:21:20.110 is very very thin it's not thick like 00:21:23.39900:21:23.409 this 00:21:23.66900:21:23.679 x5 are so I think it probably most 00:21:26.24900:21:26.259 likely is a y5 u dielectric because 00:21:30.33000:21:30.340 that's the only way to you need that a 00:21:34.08000:21:34.090 better dielectric better in terms of 00:21:36.69000:21:36.700 giving you greater capacitance for size 00:21:39.53900:21:39.549 anyway but much poorer performance so 00:21:42.93000:21:42.940 it's most likely one of those you know 00:21:44.87900:21:44.889 Wi-Fi view dielectrics because look at 00:21:46.95000:21:46.960 the physical size of a 10 microfarads 00:21:48.84000:21:48.850 but I don't know the voltage of it as 00:21:50.19000:21:50.200 well this arm x5r i've got here is a 25 00:21:53.31000:21:53.320 volt one so yeah it's a it's a betel 00:21:56.49000:21:56.500 technically a bit better dielectric and 00:21:59.00900:21:59.019 it's higher voltage hence why it's 00:22:01.35000:22:01.360 bigger so I'd be absolutely stunned 00:22:03.81000:22:03.820 if this thing produced the same 00:22:07.49900:22:07.509 frequency anyway if it does produce a 00:22:10.28900:22:10.299 tone I don't think it will I reckon 00:22:11.94000:22:11.950 there's an 80% chance I'll probably fix 00:22:14.73000:22:14.740 this thing by working in this cap let's 00:22:16.83000:22:16.840 see so did it fix it let's find out 00:22:20.55000:22:20.560 Oh can still here's something it's not 00:22:28.56000:22:28.570 the same it's not even close to being 00:22:30.66000:22:30.670 the same amplitude ah it's really I've 00:22:36.84000:22:36.850 got to put it right up right up to my 00:22:40.05000:22:40.060 ear to hear that but it still something 00:22:42.00000:22:42.010 is still there so ever it's the new 10 00:22:44.97000:22:44.980 microfarad cap or maybe it might be that 00:22:47.76000:22:47.770 charge pump cap doing a bit as well so 00:22:51.06000:22:51.070 hmm maybe change that one - all right I 00:22:54.18000:22:54.190 tried replacing the charge pump cap that 00:22:56.73000:22:56.740 one microfarad one is whacked in another 00:22:59.16000:22:59.170 crappy old the y5v I don't even know 00:23:03.54000:23:03.550 where it came from but anyway um let's 00:23:06.72000:23:06.730 have a look tongue at the right angle 00:23:10.46000:23:10.470 still there but jeez it's so low like 00:23:16.89000:23:16.900 you wouldn't even bother worrying about 00:23:19.20000:23:19.210 that it's just like that is ridiculously 00:23:23.01000:23:23.020 low I mean I don't even know if I'll be 00:23:24.84000:23:24.850 able to capture that on microphone 00:23:26.54000:23:26.550 that's what I'm getting now at the 00:23:28.62000:23:28.630 backlight on sorry I don't have any 00:23:31.44000:23:31.450 yacht sync signal anything to trigger 00:23:33.75000:23:33.760 from basically because I've disconnected 00:23:35.49000:23:35.500 the wires but I turn the backlight off 00:23:37.05000:23:37.060 and now on there's something there but 00:23:47.01000:23:47.020 it's barely picking it up and if there 00:23:49.17000:23:49.180 is something there well we're talking 00:23:52.40000:23:52.410 3.1 kilohertz now so yeah it's changed 00:23:56.01000:23:56.020 frequency which is exactly what you'd 00:23:57.96000:23:57.970 expect because you're putting a 00:24:00.03000:24:00.040 different cap in there so it is looks 00:24:02.28000:24:02.290 like it is the new 10 microfarad cap I 00:24:04.41000:24:04.420 put in there but you can see like it you 00:24:06.69000:24:06.700 basically cannot hear the thing anymore 00:24:08.73000:24:08.740 so essentially problem fixed it's just a 00:24:11.97000:24:11.980 matter of choosing the right cap some 00:24:13.59000:24:13.600 are much more susceptible than others 00:24:15.54000:24:15.550 it's going to depend on all sorts of 00:24:17.67000:24:17.680 parameters which yeah it's almost you 00:24:20.52000:24:20.530 know suck it and see really so there you 00:24:23.61000:24:23.620 go I hope you found that interesting 00:24:25.05000:24:25.060 thanks to the people on the forum and 00:24:27.39000:24:27.400 people who've bought this meter and 00:24:28.98000:24:28.990 actually reported this thing because 00:24:30.78000:24:30.790 it's something that I didn't notice it 00:24:32.46000:24:32.470 was so low but once it 00:24:34.05000:24:34.060 was reported to me you can kinda hear it 00:24:36.66000:24:36.670 but now I've essentially fixed this 00:24:38.85000:24:38.860 particular unit I've reported a 00:24:41.10000:24:41.110 deployment they're going to research it 00:24:43.53000:24:43.540 and get back to us no doubt they'll fix 00:24:45.99000:24:46.000 the issue so that's an interesting 00:24:48.15000:24:48.160 little practical example of 00:24:51.17000:24:51.180 piezoelectric effect in multi-layer 00:24:53.67000:24:53.680 ceramic capacitors watch out for it can 00:24:57.06000:24:57.070 be real trap for young player you can 00:24:58.65000:24:58.660 really come a gutter I'm ultimately 00:25:00.24000:25:00.250 though it's it's an issue with the 00:25:02.61000:25:02.620 chipset the frequency is down in the 00:25:04.59000:25:04.600 audible range and that's just dumb 00:25:06.87000:25:06.880 if they switched it at 20 kilohertz or 00:25:09.15000:25:09.160 30 kilohertz or something like that you 00:25:10.95000:25:10.960 know instead of down at 5 kilohertz no 00:25:13.71000:25:13.720 one would have noticed the thing you can 00:25:15.15000:25:15.160 go piezoelectric your dog might hear it 00:25:17.22000:25:17.230 or something like that but no your cat 00:25:19.05000:25:19.060 but that's about it so yeah it's just a 00:25:22.35000:25:22.360 poor choice of frequency the frequency 00:25:24.00000:25:24.010 might be dependent upon the capacitance 00:25:26.10000:25:26.110 though I haven't looked at it there's no 00:25:27.72000:25:27.730 details in the datasheet for that sort 00:25:29.55000:25:29.560 of things I'll link in the datasheet for 00:25:32.07000:25:32.080 the LCD controller for this thing down 00:25:34.98000:25:34.990 below which has the building lead charge 00:25:37.59000:25:37.600 bum so there you go hope you found that 00:25:39.15000:25:39.160 interesting if you did please give it a 00:25:40.56000:25:40.570 big thumbs up catch you next time 00:25:42.99000:25:43.000 ah by the way while I was playing around 00:25:45.45000:25:45.460 with this 8 and trying to get the 00:25:47.10000:25:47.110 microphone to pick this up various 00:25:49.08000:25:49.090 different types of mics I actually 00:25:50.55000:25:50.560 thought I'd try my Stanford Research 00:25:53.84000:25:53.850 filter um what is it the SR 00:25:56.61000:25:56.620 something-or-other I don't know s FS 650 00:25:59.58000:25:59.590 programmable filter you've seen in a 00:26:01.41000:26:01.420 previous video I thought oh if I can 00:26:03.57000:26:03.580 filter out all the other crap I'll get a 00:26:05.64000:26:05.650 nicer waveform and stuff like that that 00:26:08.16000:26:08.170 you know if I can like put in a bandpass 00:26:11.28000:26:11.290 filter it you know you know 3 to 6 00:26:14.25000:26:14.260 kilohertz or something then I can filter 00:26:16.08000:26:16.090 out all the other crap I'll get a nicer 00:26:17.88000:26:17.890 signal turns out the fan in this thing 00:26:20.64000:26:20.650 as I noted in the previous video I did 00:26:22.65000:26:22.660 on this I think it's just so 00:26:24.33000:26:24.340 ridiculously loud it just ruined 00:26:26.52000:26:26.530 everything so yeah time to upgrade the 00:26:29.67000:26:29.680 fan in this thing bloody Teske with 00:26:32.07000:26:32.080 noisy fans hate um 00:26:45.94000:26:45.950 you
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