Therm‐E‐Log™ — time‐temperature dosimeter

Therm‐E‐Log is an easy‐to‐read, battery‐free temperature dosimeter. Therm‐E‐Log can passively log the temperature exposure history of an article for a wide range of temperatures over a long-period (days, weeks, months, years). The device can be customized to fit multiple threshold temperature needs across a variety of industries and applications.



Therm‐E‐Log was developed as a time-temperature dosimeter to monitor the thermal history of ordnance. It can, however, be customized to fit several threshold temperature requirements and used to monitor many commodities —from ordnance to beer and wine.

Therm‐E‐Log uses specially formulated phase change materials and pigments in a compact packaging for passive and battery-free temperature recording. The custom designed faceplate can be used in dual mode – A manual Go-NoGo decision in the field or an automated mode for quality assurance personnel. Currently an Android‐based Smart phone application is under development to automate device readability and relay temperature exposure history.



Thermal Exposure Data Logging

Therm‐E‐Log records the thermal exposure history of the munitions in their transit and storage environments. Therm‐E‐Log uses phase change materials to record the thermal exposure history (time-temperature) in the device’s channels. The colorimetric indicator enables direct readability of the device. Therm‐E‐Log functions in a “start/stop/start” manner everytime the threshold temperature is exceeded and permanently records the cumulative temperature exposure history.

Long Lifespan

Therm‐E‐Log records time‐temperature exposure for long durations (goal: ten years). Currently available commercial products cannot record temperature exposure for more than a six months.


Therm‐E‐Log uses specially formulated phase change materials and colored pigments triggered by different threshold temperatures. No batteries are required as no electronic components, are used in the device.

Customizable Temperature Ranges

Therm‐E‐Log can be customized to record a wide range of temperatures (0—200 °F). Therm-E-Log’s proprietary material formulations can be created to fit this wide range of temperatures. Currently available commercial products offer a single channel device.

Four-channel Therm-E-Log device

Two-channel Therm-E-Log device


Therm‐E‐Log devices are about the size of a credit card. The compact devices can easily fit in shipping and storage containers.


The thermal exposure history recorded by Therm‐E‐Log can be read manually or by the Android-based application (under development).

Therm-E-Log records temperature exposure in the channels —the blue bar will travel up the channel when the threshold temperature is exceeded. The hours of temperature exposure can be estimated from the traveled length of the blue bar in the channel. The hours can be computed manually, however, an Android application is currently under development for automated reading.

There is also an easy‐to‐read pass/fail indicator –the red/green bar– which can be customized. If the blue bar does not exceed the length of the green bar, temperature exposure remains within the safe limits for munitions. But, if the blue bar exceeds the length of the green bar, a temperature exposure maximum has been exceeded—it is no longer safe to use the munitions.

Android-based application will make reading Therm-E-Log easier with automatic thermal exposure history computation

Simple Pass/Fail Indicator

Pass — Length of Blue bar does not exceed that of the green bar

Fail — Length of Blue bar exceeds that of the green bar


Therm-E-Log can be used to monitor commodities for the medical and pharmaceutical industries. Integration of Therm-E-Log devices into the supply-chain of temperature sensitive shipments, such as food and perishables, is easy because of its compact size and battery-free operation.