Maxim DS18B20 - Real or Fake/Knockoff?

Other Hardware Sensors
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I have been using these DS18B20 sensors for a couple years now. Some have
held up over time and some have not. Unfortunately in more than one instance they have
gotten "squirrelly" on me & I am fairly confident my mounting & termination practices are sound.

I wanted to share some information that hopefully is not a repeat of someone else's
input or something already found on this platform. If it is my apologies.

This is an excellent article on the DS18B20s about their component makeup:
Real or Fake?

This is the GitHub link for the authentication code:
INO Sketch:

I paid about $5 a piece w/ shp for each sensor from Newark Electronics for these little suckers! Not cheap... for me anyway.
But they are directly sourced from Analog Devices who makes the "real deal" Maxim sensors.
So now I know I have authentic DSBs and will see how they perform over time compared
to the ubiquitous knockoffs that are 1/4 the price. I guess you get what you pay for in some instances. I am not pushing Newark products and I think DigiKey sells the same ones. Whether the software is actually reliable remains to be seen but it definitely can tell
a difference bewteen different sensors.

Manufacturer: Analog Devices
Mfr part number: DS18B20+T&R [the T&R means they come on a glue paper strip
and the outer legs are prebent to about 45 degrees.]
Newark link:

Sketch code ouput testing two different sources:

Bad check of Knockoff:

28-AC-27-96-F0-01-3C-2A: ROM does not follow expected pattern 28-xx-xx-xx-xx-00-00-crc. Error.
  Scratchpad Register: A6/01/55/05/7F/A5/A5/66/DB
  Info only: Scratchpad bytes 2,3,4 (55/05/7F):  not Maxim default values 4B/46/7F.
  Scratchpad byte 5 (0xA5):  should have been 0xFF according to datasheet. Error.
  Scratchpad byte 6 (0xA5):  unexpected value. Error.
  Scratchpad byte 7 (0x66):  should have been 0x10 according to datasheet. Error.
  0x4E modifies alarm registers:  ok.
  0x4E accepts 10 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  0x4E accepts 12 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  Checking byte 6 upon temperature change: not necessary. Skipped.
  --> Sensor appears to be counterfeit based on 4 deviations.

// Good check of Authentic:

28-F9-9F-16-0F-00-00-4C: ROM ok.
  Scratchpad Register: 35/01/4B/46/7F/FF/0B/10/31
  Info only: Scratchpad bytes 2,3,4 (4B/46/7F):  Maxim default values.
  Scratchpad byte 5 (0xFF):  ok.
  Scratchpad byte 6 (0x0B):  ok.
  Scratchpad byte 7 (0x10):  ok.
  0x4E modifies alarm registers:  ok.
  0x4E accepts 10 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  0x4E accepts 12 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  Checking byte 6 upon temperature change: not necessary. Skipped.
  --> Sensor responded like a genuie Maxim.
      Not tested: EEPROM, Parasite Power, and undocumented commands.
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I've used that sketch in the past and found it to be an accurate test of whether or not a DS18B20 is the real thing or not.

The other excellent way of telling, as you noted, is how much you paid for it and where you bought it from. :slight_smile:

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