--- title: Identify Fake Metal Film Resistor tags: electronics, measurment --- # Identify Fake Metal Film Resistor One way to do that, you can visual inspenction by destructive way. Another way is, we don't care that is Metal or Carbon actually. One characteristics that have good resistor is **low TCR**. low TCR is expected for the Metal Film Resistor (relativery Carbon Film). so, I try to comparison known resistor and cheap one. it's OK; that is a Carbon but, somehow achieve low TCR by Alien Technology. it's not OK; that is a Metal Film but very high TCR, which is not expected to Metal Film. **"accuracy/tolerance" doesn't mean anything**. 1% resistor doesn't mean metal film. Instrument: - Heater Element (+ Variable Power Supply) - Thermometer - Multimeter or Ohmmeter - Resistors for test ![setup](https://i.imgur.com/wRlS15X.jpg) --- ### Known Carbon Film Resistor 1K 5% ![](https://i.imgur.com/wIlyV6i.jpg) CFS50J1KB [datasheet](http://akizukidenshi.com/download/ds/faithful/R1_CF.pdf) <br> ### Known Metal Film Resistor 1K 1% ![](https://i.imgur.com/XDYLQUg.png) MFS25F1KRB [datasheet](http://akizukidenshi.com/download/ds/faithful/mf.pdf) <br> ### Cheap Resistor: that claim Metal Film 1K 1% ![](https://i.imgur.com/fBDJ1fU.png) no datasheet. but you can find this everywhere. looks like Metal Film, because of blue-ish color. ## Result ```python # measured data faithful_link_carbon_film = [ # temp, reading (26.4, 1004.0), (29.8, 1003.3), (32.7, 1002.7), (42.2, 1000.9), (54.6, 998.4) # 700mA for heater element ] faithful_link_metal_film =[ (27.6, 1002.1), (31.3, 1002.0), (42.8, 1001.7), (59.1, 1001.3) ] unknown_cheapie = [ (27.6, 992.6), (31.0, 991.9), (34.5, 991.1), (42.7, 989.1), (60.0, 985.3) ] ``` ```python %matplotlib inline import matplotlib.pyplot as plt fig, ax = plt.subplots(figsize=(8, 4)) ax.plot(*zip(*faithful_link_carbon_film), marker='o', markersize=4, label='Known CarbonFilm') ax.plot(*zip(*faithful_link_metal_film), marker='o', markersize=4, label='Known MetalFilm') ax.plot(*zip(*unknown_cheapie), marker='o', markersize=4, label='Unknown Cheapie') plt.title('Temperature Coefficient') plt.xlabel('℃') plt.ylabel('Ω') ax.legend() None ``` ![Result Graph](https://i.imgur.com/0FStPXa.png) note: Cheapie exceeds 1% range at 37C. --- I use this function, for calculating TCR. ```python def tcr_ppm(test_result): # JIS-C 5201-1:2011 lo, hi = test_result[0], test_result[-1] temp_diff = hi[0] - lo[0] ohm_diff = hi[1] - lo[1] return (ohm_diff / (lo[1] * temp_diff)) * 10 ** 6 ``` |Resistor | Measured TCR | |-------- | ------ | |Known Carbon Film |-197.79 ppm/K| |Known Metal Film |-25.34 ppm/K| |Unknown Cheapie |**-226.99 ppm/K**| it's definitely NOT Metal Film. (... or maybe Metal Film, with horrible TCR somehow.) --- ### another resistors |Resistor |datasheet/info| Measured TCR | |-------- | ------ | ------ | |RL20S472G |[datasheet](https://jp.onlinecomponents.com/dale/rl20s472g-11219050.html)|-13.19 ppm/K| |KOA SF-1/4|[datasheet](https://www.ttiinc.com/content/ttiinc/en/manufacturers/k-o/koa/products/sf-metal-film-resistor-koa.html)|-1.63 ppm/K| |Pt100 |(it's RTD!, just for fun)| 3885.41 ppm/K (expected)| |Chian Chia / Metal Film|From LCSC| 38.10 ppm/K| |Uniroyal Elec / Metal Film |From LCSC| 16.16 ppm/K| --- ## note & link - [Faithful Link Industorial corp](http://www.faithfullink-ind.com/pro.php?f=5&cid=8): used Known Resistor - [MUFF WIGGLER :: View topic - The fake MF resistor saga](https://www.muffwiggler.com/forum/viewtopic.php?p=908844) - [electro-music.com :: View topic - Be very careful when ordering resistors from china !](http://electro-music.com/forum/viewtopic.php?t=31860) - [Counterfeit Examples Electronic Components](http://www.cti-us.com/pdf/CCAP-101InspectExamplesA6.pdf) page 110 --- <br> ##### btw - 100ppm/K is - 0.01%/K - 0.1%/10K - 1%/100K