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Measuring capacitance without desoldering capacitors from a PCB - is it possible
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00:00:12.240 hello today we are going to be talking 00:00:14.61000:00:14.620 about measuring capacitance however we 00:00:17.04000:00:17.050 aren't going to be performing just any 00:00:18.51000:00:18.520 old capacitance measurements but 00:00:20.09900:00:20.109 measurements without desoldering 00:00:21.48000:00:21.490 capacitors from a PCB over the past 00:00:23.82000:00:23.830 several years different websites have 00:00:25.65000:00:25.660 offered various devices that measure 00:00:27.08900:00:27.099 capacitance and other details of 00:00:28.95000:00:28.960 capacitors without desoldering them from 00:00:31.10900:00:31.119 a PCB there's been lots of discussion on 00:00:33.47900:00:33.489 different forums some people say that 00:00:35.52000:00:35.530 they purchased them others don't 00:00:37.26000:00:37.270 recommend it etc all of these 00:00:39.00000:00:39.010 discussions raise two questions for me 00:00:41.01000:00:41.020 first of all why do the products listed 00:00:43.35000:00:43.360 never include well-known manufacturers 00:00:45.45000:00:45.460 like fluke app' unity mass tech etc that 00:00:49.17000:00:49.180 seems to imply that none of the most 00:00:50.79000:00:50.800 trusted brands produce any of this type 00:00:52.77000:00:52.780 of device the second question is 00:00:54.77900:00:54.789 strictly technical it's based on 00:00:56.49000:00:56.500 elementary knowledge of school physics 00:00:58.29000:00:58.300 at school we are taught that if two 00:01:00.77900:01:00.789 capacitors are connected in parallel 00:01:02.13000:01:02.140 their equivalent capacitance will be 00:01:04.22900:01:04.239 equal to the sum of their individual 00:01:06.17900:01:06.189 capacitances however if they are in a 00:01:08.34000:01:08.350 series then we have a more complicated 00:01:10.08000:01:10.090 formula we have to deal with inverted 00:01:12.30000:01:12.310 values so 1 divided by c equals 1 00:01:15.45000:01:15.460 divided by c 1 plus 1 divided by c 2 00:01:17.85000:01:17.860 here we have a PCB and we want to 00:01:20.34000:01:20.350 measure the capacitance of this 00:01:21.78000:01:21.790 capacitor its contacts are right here 00:01:23.96900:01:23.979 when we connect a multimeter or another 00:01:26.07000:01:26.080 device that measures capacitance to 00:01:27.78000:01:27.790 those contacts we will obtain a value of 00:01:29.96900:01:29.979 the actual capacitance only if one 00:01:32.03900:01:32.049 single element this capacitor is 00:01:34.20000:01:34.210 soldered between these two points here 00:01:36.14900:01:36.159 we have to remember that there's more 00:01:37.71000:01:37.720 within one element on the PCB in fact 00:01:40.49900:01:40.509 there are more than a hundred therefore 00:01:43.35000:01:43.360 the capacitance between these two points 00:01:45.24000:01:45.250 would be really hard to calculate this 00:01:47.70000:01:47.710 is why even theoretically based on the 00:01:50.31000:01:50.320 knowledge of school physics is not 00:01:52.01000:01:52.020 possible to measure the capacitance of 00:01:54.42000:01:54.430 an element without desoldering it from a 00:01:56.94000:01:56.950 PCB enough with theory though let's move 00:02:00.63000:02:00.640 on to the real world 00:02:02.91000:02:02.920 we will conduct an Eevee experiment with 00:02:05.77000:02:05.780 a number of different measurements on 00:02:07.20900:02:07.219 this PCB as you can see it has many 00:02:10.15000:02:10.160 different components electrolytic 00:02:12.46000:02:12.470 capacitors SMD capacitors inductors 00:02:16.50000:02:16.510 resistors microchips light-emitting 00:02:19.00000:02:19.010 diodes it has the works we will conduct 00:02:22.18000:02:22.190 our measurements in different phases I 00:02:24.53900:02:24.549 have already completed the first one by 00:02:27.03900:02:27.049 writing down all of the nominal 00:02:28.39000:02:28.400 capacitance values in the points where 00:02:30.40000:02:30.410 measurements will be taken there's one 00:02:33.00900:02:33.019 exception 00:02:34.02000:02:34.030 there is no capacitor in point five as 00:02:37.24000:02:37.250 it has been previously removed just for 00:02:40.36000:02:40.370 kicks we will measure the capacitance in 00:02:42.19000:02:42.200 this point as well in Phase two we will 00:02:46.36000:02:46.370 measure the capacitance of those points 00:02:47.92000:02:47.930 without desoldering the capacitors in 00:02:49.53900:02:49.549 Phase three I will decide are all 00:02:51.61000:02:51.620 capacitors measure their capacitance as 00:02:53.80000:02:53.810 usual and record the values we will then 00:02:56.34900:02:56.359 compare them to the original values and 00:02:58.11900:02:58.129 find a result let's begin we'll turn on 00:03:01.05900:03:01.069 the multimeter as you can see I chose a 00:03:04.36000:03:04.370 unity UT 139 C because it measures 00:03:08.08000:03:08.090 capacitance very well we also have 00:03:10.39000:03:10.400 another video about this so let's 00:03:13.62900:03:13.639 measure point 1 the capacitance is 00:03:23.97000:03:23.980 one hundred microfarads 00:03:27.48000:03:27.490 it's supposed to be 47 we already see an 00:03:31.36000:03:31.370 inconsistency point - let me try again 00:03:45.51000:03:45.520 somewhere close to 164 164 microfarads 00:03:54.75000:03:54.760 obviously its capacitance is 00:03:56.74000:03:56.750 significantly different from the value 00:03:58.27000:03:58.280 printed on the capacitor in point three 00:04:04.39000:04:04.400 we should have four hundred and seventy 00:04:05.89000:04:05.900 micro for ads however we get almost one 00:04:13.21000:04:13.220 militar at this is two times as high 00:04:18.33000:04:18.340 let's record this the capacitance should 00:04:25.45000:04:25.460 be 47 in point four 00:04:33.09000:04:33.100 and it's about 164 microphones 00:04:45.72000:04:45.730 in point five right here there's no 00:04:48.99000:04:49.000 capacitor but for the accuracy of the 00:04:51.81000:04:51.820 experiment let's measure it as well what 00:05:00.27000:05:00.280 can I say it looks like we have an 00:05:02.55000:05:02.560 invisible capacitor on the PCB with a 00:05:04.95000:05:04.960 capacitance of 58 micro farad's 00:05:07.86000:05:07.870 we should patent this technology I will 00:05:16.68000:05:16.690 also record zero in this slot as there 00:05:19.44000:05:19.450 is no capacitor here lastly point six we 00:05:24.12000:05:24.130 should have 100 microfarads let's see 00:05:27.21000:05:27.220 what we get 00:05:36.61000:05:36.620 sixty-six microphones this is the most 00:05:47.81000:05:47.820 accurate measurement so far with a 00:05:49.79000:05:49.800 thirty five percent error as you can see 00:05:53.03000:05:53.040 from this first step if we measure 00:05:54.53000:05:54.540 capacitance without desoldering 00:05:56.00000:05:56.010 capacitors from the PCB there is a big 00:05:58.85000:05:58.860 difference between the nominal or stated 00:06:01.25000:06:01.260 values and the measured values we will 00:06:04.34000:06:04.350 now disorder and measure them in a more 00:06:06.29000:06:06.300 correct way it is possible that some of 00:06:09.23000:06:09.240 the capacitors capacitance has changed 00:06:11.48000:06:11.490 over time 00:06:41.38000:06:41.390 capacitor number three number four there 00:07:03.59000:07:03.600 is no capacitor number five and number 00:07:08.78000:07:08.790 six this soldering iron tip is not very 00:07:12.11000:07:12.120 convenient for tasks like these a bigger 00:07:15.11000:07:15.120 one would have been better 00:07:31.49000:07:31.500 so I have D soldered the capacitors now 00:07:35.67000:07:35.680 let's measure their actual capacitance 00:07:40.82000:07:40.830 it looks like our multimeter has 00:07:43.08000:07:43.090 automatically switched off we will use a 00:07:47.64000:07:47.650 different test lead this time as the 00:07:49.67000:07:49.680 standard one is not convenient for this 00:07:52.11000:07:52.120 type of measurement that's because the 00:07:54.84000:07:54.850 capacitor leads are gone 00:08:13.72000:08:13.730 as you can see this one has a 00:08:17.20000:08:17.210 capacitance of 67 microphones 00:08:49.22000:08:49.230 and this one has 46 microphones the same 00:08:55.59000:08:55.600 as the value printed on the capacitor 00:09:07.30000:09:07.310 capacitor number three its capacitance 00:09:10.34000:09:10.350 should be 470 micro farad's 00:09:25.93000:09:25.940 445 00:10:02.81900:10:02.829 here it's 49 microphones and in our 00:10:11.40900:10:11.419 first or in this case our last capacitor 00:10:14.19900:10:14.209 with a printed value of 47 microphones 00:10:17.04900:10:17.059 and a measured value on the PCB of 00:10:19.23900:10:19.249 around 100 about 48 microphones 00:10:40.57000:10:40.580 the results speak for themselves the 00:10:43.70000:10:43.710 capacitance values are incorrect in 00:10:45.32000:10:45.330 every point except the last one but this 00:10:48.17000:10:48.180 is an exception to the rule rather than 00:10:50.09000:10:50.100 proof here we didn't even have a 00:10:52.82000:10:52.830 capacitor and we measured 58 microflora 00:10:55.46000:10:55.470 ads over here we had a stated 00:10:57.83000:10:57.840 capacitance of 47 microphones we 00:11:00.29000:11:00.300 measured it on the PCB at 164 and it 00:11:03.77000:11:03.780 turned out to actually be somewhere 00:11:05.48000:11:05.490 around 46 to 47 here the measured 00:11:08.72000:11:08.730 capacitance was almost twice as high as 00:11:10.79000:11:10.800 the actual one the same here with 164 00:11:16.19000:11:16.200 microphones when it should have been 49 00:11:18.70000:11:18.710 here we measured 100 microfarads in the 00:11:21.71000:11:21.720 PCB but it's actual capacitance is a 00:11:24.11000:11:24.120 mere 48 microphones so as we can clearly 00:11:27.41000:11:27.420 see the measurements that are in the 00:11:29.99000:11:30.000 second column are not measurements at 00:11:32.12000:11:32.130 all they are more like a lottery number 00:11:34.52000:11:34.530 from a fortune cookie some may say that 00:11:36.92000:11:36.930 I wasn't using a special RLC meter that 00:11:39.26000:11:39.270 measures ESR but regular multimeter 00:11:41.36000:11:41.370 instead first of all this multimeter 00:11:44.45000:11:44.460 measures capacitance very accurately as 00:11:46.85000:11:46.860 we have previously shown secondly what 00:11:50.03000:11:50.040 is ESR it's basically a series of 00:11:53.29000:11:53.300 resistances therefore no matter what you 00:11:56.69000:11:56.700 use for your measurements even if it's 00:11:59.27000:11:59.280 the best device for measuring 00:12:00.92000:12:00.930 capacitance you cannot measure the ESR 00:12:03.62000:12:03.630 of an individual capacitor instead you 00:12:06.44000:12:06.450 will end up measuring an equivalent 00:12:07.85000:12:07.860 value of the entire circuit many devices 00:12:10.91000:12:10.920 present themselves as tools that can 00:12:12.56000:12:12.570 measure capacitance without desoldering 00:12:14.24000:12:14.250 the elements of a PCB most of the 00:12:17.84000:12:17.850 descriptions written online have one 00:12:19.52000:12:19.530 main idea a small voltage is applied to 00:12:24.44000:12:24.450 these points in a way that supposedly 00:12:26.66000:12:26.670 doesn't affect anything surrounding them 00:12:28.76000:12:28.770 just this small area so this capacitor 00:12:32.45000:12:32.460 will not be affected anymore and it will 00:12:34.52000:12:34.530 not take part in the measurements but 00:12:36.83000:12:36.840 that's all bogus because it's impossible 00:12:39.17000:12:39.180 to measure this capacitor if there are a 00:12:41.81000:12:41.820 lot of other things here on the PCB you 00:12:45.65000:12:45.660 can measure anything else you want but 00:12:47.66000:12:47.670 not the capacitor 00:12:49.19000:12:49.200 actually you can measure an equivalent 00:12:52.04000:12:52.050 capacitance but not the capacitance of 00:12:55.04000:12:55.050 this particular capacitor by itself 00:12:57.92000:12:57.930 therefore do not buy these devices 00:13:01.00000:13:01.010 instead by regular quality multimeters 00:13:04.46000:13:04.470 you don't necessarily need this one even 00:13:07.40000:13:07.410 just make sure you buy regular measuring 00:13:09.94900:13:09.959 equipment from good manufacturers and 00:13:11.96000:13:11.970 measure things properly in this video I 00:13:14.99000:13:15.000 have shown you that measuring 00:13:16.10000:13:16.11000:13:17.62900:13:17.639 capacitors from a PCB is a myth please 00:13:20.75000:13:20.760 like this video if you found it useful 00:13:22.28000:13:22.290 and subscribe to our Channel we hope you 00:13:24.25900:13:24.269 have a great day and take correct 00:13:25.75900:13:25.769 measurements
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