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I bought three "LM35DZ" temperature sensors, all of them are from National Semiconductor.

When I connect +5 V (4.90 V actually) to the Vcc pin, and its GND pin to 0 V, I get 0 V of output voltage with reference to ground, but when I measure Vcc with Vout pin as reference I get 4.36 V of voltage drop. There is no current flowing through the sensor as I checked with the multimeter (one lead to the GND pin of the LM35 and the other to 0 V of the voltage source.)

I have the same problem with all of them, what am I doing wrong? Did I burn them?

The TO-92 casing also says "52AB" (52AB LM35 DZ.) I couldn't find any info about the 52AB part.

Here is an image showing how I am doing the connections:

enter image description here

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  • \$\begingroup\$ it is not clear what problem you are seeing ... looks like you described normal readings if your voltmeter is not very accurate \$\endgroup\$
    – jsotola
    Nov 13, 2022 at 19:59
  • \$\begingroup\$ Check the pinout, maybe you mixed out. Pin 1 is on left then you looking at face. \$\endgroup\$
    – user263983
    Nov 13, 2022 at 20:28
  • \$\begingroup\$ @user263983 I checked the pin out, the Vcc pin is one the left and the ground pin is on the right, while the Vout pin is in the middle, all of this when the flat side is towards you. \$\endgroup\$
    – ThreeNamesGrace
    Nov 13, 2022 at 20:58
  • \$\begingroup\$ @jsotola My multimeter has a resolution up to 0.1 mV, I don't think it is faulty, I tested it with a 1 Ohm and 1 kOmh (976 Ohm according to the multimeter) voltage divider with 4.57 VDC of voltage supply, it shows 4.5 mV of voltage drop for the 1 Ohm resistor which is near to the theorical 4.68 mV that I should get using the voltage divider formula. \$\endgroup\$
    – ThreeNamesGrace
    Nov 13, 2022 at 21:14

3 Answers 3

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The output should read ~250mV wrt ground at 25°C Ta.

Maybe they are non-functional fakes.

The probability likely approaches 100% if you bought them from some dubious source. (image from linked YT video).

enter image description here

The 52AB should be a lot code/date code but it may also be used to identify suspect chips. Note this comment from July this year:

Pode confirmar qual lote você tem,? Pois tem 2 lotes no mercado que comprei e estão com problema, o lote 89015 e o lote 52ab não funcionamDenunciar

Which translates to:

Can you confirm which batch you have? Because there are 2 lots on the market that I bought and they are having a problem, lot 89015 and lot 52ab do not work.

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    \$\begingroup\$ That explains everything, I just bought faulty or fake ones, I even supplied 12 VDC to one of them and it blew up. Thanks for your answer. \$\endgroup\$
    – ThreeNamesGrace
    Nov 13, 2022 at 21:17
  • \$\begingroup\$ It's surprising that these sensors are from National Semiconductor. Texas Instruments acquired National Semiconductor in 2011. \$\endgroup\$
    – Nick Alexeev
    Nov 14, 2022 at 3:40
  • \$\begingroup\$ @NickAlexeev Yes, I'm not sure they've eliminated the NS logo from all products, but that's suspicious to me as well. I deleted my comment on it because some photos still show NS. \$\endgroup\$
    – Spehro Pefhany
    Nov 14, 2022 at 3:47
  • \$\begingroup\$ @NickAlexeev NS logo is still present on very few TI analog parts I've bought directly from TI just a year ago. It's a rarity though. I didn't buy any LM35, so I can't say whether they were recently sold under that logo or not. I have about as much love for fake chip vendors as I do for catalytic converter thieves. Both would be a reason to bring public lashings back as a punishment for those specific activities. Both are disproportionately disruptive to the society at large. \$\endgroup\$
    – Kuba hasn't forgotten Monica
    Jan 2 at 22:23
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The 52AB batch are fakes. If you test them with multimeter they are behaving like NPN transistors.

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  • \$\begingroup\$ I applied 12V to one of those and it exploded, the datasheet says that it can support up to 20V. \$\endgroup\$
    – ThreeNamesGrace
    Sep 28 at 22:24
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I also have an LM35 with the 89015 code written on it. Tried to use it multiple times, and every time I tried i got insanely unrealistic values. I think they are fake too :/

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