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DS1921H, DS1921Z

High-Resolution Thermochron iButton Devices

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Status Explanations for product status codes

Part Number Status
DS1921H Active: In Production. See Ordering Information for details.
DS1921Z Active: In Production. See Ordering Information for details.


The Thermochron® iButton® devices (DS1921H/Z) are rugged, self-sufficient systems that measure temperature and record the result in a protected memory section. The recording is done at a user-defined rate, both as a direct storage of temperature values as well as in the form of a histogram. Up to 2048 temperature values taken at equidistant intervals ranging from 1 to 255 minutes can be stored. The histogram provides 64 data bins with a resolution of 0.5°C. If the temperature leaves a user-programmable range, the DS1921H/Z will also record when this happened, for how long the temperature stayed outside the permitted range, and if the temperature was too high or too low. Additional 512 bytes of general-purpose battery-backed SRAM allow storing information pertaining to the object to which the DS1921H/Z is associated. Data is transferred serially via the 1-Wire® protocol, which requires only a single data lead and a ground return. Every DS1921H/Z is factory-lasered with a guaranteed unique electrically readable 64-bit registration number that allows for absolute traceability. The durable stainless steel package is highly resistant to environmental hazards such as dirt, moisture, and shock. Accessories permit the DS1921H/Z to be mounted on almost any object, including containers, pallets, and bags.

Data Sheet

Download this datasheet in PDF formatDownload Rev 10 (PDF, 472.7kB)
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An evaluation board is available: DS1921K

This product contains lithium-metal batteries. See applicable regulations for transport requirements for batteries in equipment.

Key Features

  • Digital thermometer measures temperature 1/8°C increments with ±1°C accuracy
  • Built-in real-time clock (RTC) and timer has accuracy of ±2 minutes per month from 0°C to 45°C
  • Water resistant or waterproof if placed inside DS9107 iButton capsule (Exceeds Water Resistant 3 ATM requirements)
  • Automatically wakes up and measures temperature at user-programmable intervals from 1 to 255 minutes
  • Logs consecutive temperature measurements in 2KB of datalog memory
  • Records a long-term temperature histogram with 1/2°C resolution
  • Programmable temperature-high and temperature-low alarm trip points
  • Records up to 24 time stamps and durations when temperature leaves the range specified by the trip points
  • 512 bytes of general-purpose battery-backed SRAM
  • Communicates to host with a single digital signal at 15.4kbits or 125kbits per second using 1-Wire protocol
  • Fixed range: H: +15°C to +46°C; Z: -5°C to +26°C
Common iButton Features
  • Digital identification and information by momentary contact
  • Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
  • Multidrop controller for 1-Wire net
  • Chip-based data carrier compactly stores information
  • Data can be accessed while affixed to object
  • Button shape is self-aligning with cup-shaped probes
  • Durable stainless steel case engraved with registration number withstands harsh environments
  • Easily affixed with self-stick adhesive backing, latched by its flange, or locked with a ring pressed onto its rim
  • Presence detector acknowledges when reader first applies voltage

Key Specifications:

iButton Products
Part Number Technology Applications Memory Type Memory Size Data Logger Type Data Logger Size Data Logger Sample Rate Data Logger Histogram Data Logger Accuracy Data Logger Resolution Data Logger Measuremt. Range Prog. Alarm Unique Ware Real Time Clock Budgetary
See Notes
DS1921H  iButton
Asset Management
Temperature Data Logging
NV SRAM 4K bits Temperature 2048 Byte 1min to 255min 64-bin ±1°C 0.125°C +15°C to +46°C Temperature High/Low No Yes $14.54 @1k
DS1921Z  63-bin -5°C to +26°C
See All iButton Products (26)

Pricing Notes:

This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.


DS1921H, DS1921Z: High Resolution Thermochron
High Resolution Thermochron

More Information

New Product Press Release   2002-02-04 ]

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Document Ref.: 19-4887 Rev 10; 2013-12-05
This page last modified: 2013-12-05