Chris Petrich Warns "Almost All" DS18B20 Sensors Not Bought From Authorized Distributors Are Fake

Engineer Chris Petrich has warned of a glut of DS18B20 temperature sensors hitting the market, in quantities large enough that "almost all" of a 1,000-unit batch purchased from over 70 different vendors proved to be fakes.

The DS18B20 is a popular temperature sensors thanks to its low cost, small size, and ability to be included in a waterproof package. We've seen it used for everything from Bluetooth-connected beer homebrewing setups to indoor greenhouses and PCB etching stations - but evidence suggests that many of these projects could have been unwittingly using fakes.

In a GitHub repository highlighted by CNX Software, Petrich warns that unless DS18B20 sensors were purchased directly from the manufacturing, Maxim Integrated, or through an authorized distributor, they're almost certain to be fakes — and he has the data to prove it.

"We bought over 1000 'waterproof' probes or bare chips from more than 70 different vendors on eBay, AliExpress, and online stores — big and small — in 2019," Petrich writes. "All of the probes bought on eBay and AliExpress contained counterfeit DS18B20 sensors, and almost all sensors bought on those two sites were counterfeit."

"Besides ethical concerns, some of the counterfeit sensors actually do not work in parasitic power mode, have a high noise level, temperature offset outside the advertised ±0.5 °C band, do not contain an EEPROM, have bugs and unspecified failure rates, or differ in another unknown manner from the specifications in the Maxim datasheet. Clearly, the problems are not big enough to discourage people from buying probes on eBay, but it may be good to know the actual specs when the data are important or measurement conditions are difficult."

To assist with finding the fakes, Petrich has released two Arduino sketches under the permissive Apache License. The first sketch tests supposed DS18B20 sensors and determines whether it's likely to be a fake; the second classifies to which family of fakes the counterfeit component belongs — but comes with the warning that it could damage the component under test, an issue not shared by the first sketch.

The counterfeit families discovered by Petrich and colleagues, through testing and observation of de-capped components, include parts which appear to be authentic but misappropriated from the proper supply chain, clones with poor temperature performance, clones with the correct temperature offset curves and a range with increasingly inaccurate offsets, "noisy rubbish," and obsolete parts.

A full list of the counterfeits, and how to spot them, can be found on GitHub along with the source code for the two Arduino sketches.