IButton temperature logger

Tool Infobox
Related topics	Body temperature tracking
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The Thermocron iButton is a small hardware device that records the temperature every five minutes onto its non-removable memory. No network (Bluetooth, Wifi, etc.) is required. No other device is required until you want to transfer the logs to a computer to read them.

Example CSV output

10/9/21, 8:37:46 PM,C,26.125
10/9/21, 8:42:46 PM,C,28.562
10/9/21, 8:47:46 PM,C,31

Driver and viewer

• Windows
• Mac: appears to be Intel specific
• Mac: instructions for ARM chip
• Linux

Description & Tips

Description taken from circadiaware

Wrist skin temperature sensor for circadian rhythm phase assessment: Maxim Thermocron iButton DS1925EVKIT (Starter kit including one DS1925L iButton and the DS9490R and DS1402D-DR8+ connectors to retrieve the iButton's data on computers via USB as a CSV file). Cost: about ~$100. If DS1925L is unavailable, can also use DS1922L but the internal memory and battery are much shorter (4 years for DS1925L with 5min sampling rate (setup 300s in the config), 6 months for DS1922L for 2min sampling rate). The iButton does not need to be recharged, but unfortunately once it runs out of battery, it cannot be replaced (although there is one academic paper which shows how to replace an iButton's battery, but this is not an official instruction, do it at your own risk, and of course the device will be much less airtight after).

• Advantages: this is a cheaper alternative to GreenTEG CORE. Wrist skin temperature has no delay, it shows the current state of the circadian phase, whereas core body temperature lags behind by a hour or two due to thermoregulation lag.
• Disadvantages: rarely painful on the wrist especially when using a brand new cotton sport wristband until it loosen with use, clunky software suite (no smartphone app, transfert is wired via USB, need to export to CSV and then plot yourself the data or use Circalizer), prone to bias (the cotton wristband insulates the iButton from environment but still skin temperature can be biased by a lot of environmental factors, and it's just more noisy by nature compared to core body temperature).
• Interpretation tips: opposite of the core body temperature: a steep increase of wrist skin temperature signals the start of the circadian night, while a slow decrease signals its end and the start of the circadian morning and day. There is no time lag. The data needs to be smoothed because it is very noisy.
• Tips for usage:
  • Buy a cotton sports wrist band such as is used for tennis ("sweat bands"). The Under Armour wristbands are recommended, they exist in various lengths, even tiny ones which are great during summer.
  • Buy also velcro stripes (hooks type, not loop) with adhesive, to glue on the iButton and then attach it on the inside of the cotton sports wrist band (the velcro hooks will hook well on the cotton as it naturally forms loops).
  • How to wear: Wear the cotton wristband + iButton on the non-dominant arm, and place the iButton on contact with the skin, positioned at about the middle of the width of the arm to be on the radial artery. Technically, the radiar artery runs from the wrist to the elbow's interior, so you can place the iButton anywhere on the length of the forearm. In fact, you should regularly move the wristband up and down your forearm, to avoid the sweat and warmth accumulation from itching and damaging the skin (move twice a day at least, and whenever it's itching). If necessary, the wristband can be placed on the dominant arm for some time if you need the non-dominant one to rest.
  • This setup provides true 24/7 skin temperature monitoring setup, as the iButton DS1925L can last 4 years with its integrated battery (then need to buy another one or can try to manually replace the battery as some researchers have done).
  • Data need to be transferred to a computer every 6 months (for the DS1925L, the interval is much smaller with DS1922L, about 10 days), and the device memory (mission) needs to be reset, otherwise it will stop recording new records.