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iButton - Thermochron® / Hygrochron™

What is an iButton?

The Maxim/Dallas iButton® is a computer chip enclosed in a 16mm stainless steel can. iButtons are rugged enough to withstand harsh environments, indoors or outdoors. Each iButton has a unique and unalterable address that is laser etched onto its chip inside the can. The address can be used as a key or identifier for each iButton.

All iButtons use their stainless steel "Can" for their electronic communications interface. By simply touching each of the two contacts you can communicate to any of the iButtons by using our 1-Wire® protocol.

For more information see What is an iButton? on the iButton homepage (Maxim/Dallas).


The Thermochron® iButton is a discrete temperature data logger which integrates a thermometer, a clock/calendar and up to 8192 bytes of memory. The iButton logs data for more than 10 years depending on the kind of mission. There are several Thermochrons from which to choose with a wide temperature range of -40°C to 125°C.

The DS1921 are standard Thermochrons. The DS1922x are high-capacity Thermochrons with more logging memory, increased accuracy, and increased resolution.

The stainless-steel casing of a Thermochron makes it rugged, reusable, and portable. For applications such as cold-chain shipping (EN 12830) , process monitoring/quality control, and refrigerator/freezer system tracking. It is so small that it fits anywhere and can deliver years of reliable, highly accurate temperature readings.


DS1921G , DS1921H+Z



The Hygrochron™ iButtons (DS1923) adds an embedded humidity sensor to the temperature-logging capability of the high-capacity Thermochron family to create a data logger that records both temperature and humidity.

The tiny opening in the lid of the Hygrochron iButton employs a special filter that allows water vapor to pass through and reach the internal humidity sensor, but repels liquid-phase water.




Thermochron iButtons can be mounted virtually anywhere, up-to-date information can travel with a person or object anywhere they go. You can expose it to high or low temperature extremes, step on it or drop it in water.

Reading mission results or start a new mission is done with a PC. The Thermochron iButton connects to a Blue Dot receptor which in turn is connected to a 1-Wire Adapter attached to a computer.

Thermo23 software explores and initializes the whole family of Thermochron and Hygrochron iButtons. You may download an evaluation version of Thermo23. However, measuring intervals of this test version are set at a random value. System requirements are standard Windows PC (2000/XP/Vista) with an attached 1-Wire-Net Adapter.


More information:

  • Applications – how Thermochron and Hygrochron iButtons are used.
  • Thermo23 - Software used to explore and initialize all Thermochron iButtons.
  • Download – get an evaluation version of Thermo23.


iButton homepage by Maxim/Dallas: