I finally got around to testing the GY-906 BAA IR temperature sensors. The test results indicate that measuring the temperature of IV fluid through IV tubing is not only possible with IR temperature sensors but also can likely achieve something close to +/- 1°C accuracy! I was pleasantly surprised and this was such a great way to close out this project. 

Testing of the IR temperature sensor involved using the sous vide cooker to warm water to several different temperature setpoints then pump the water through an IV tube and detect the temperature using a GY-906. 

To get a good reading from the IR temperature sensor, I had to place the IV in direct contact with the senor and apply a very small amount of pressure on the IV tube to push it against the sensor.

IR temperature sensor readings for six water bath setpoints between 20-60°C are shown in the table below. No sensor reading deviated by more than 0.7°C from the water bath setpoint temperature.

I am still surprised by the accuracy of the results. My first thought was that I may have been too quick to dismiss using a thermistor on the outside of IV tube to get an accurate temperature reading. So I hooked up a couple thermistors I had on hand. The temperature response was at least ten times worse than the IR temperature sensor and the thermistors would only read 47-49°C when the water bath setpoint was 70°C.

It's pretty cool to find that a <$10 part can be used to accurately measure IV fluid temperature through an IV tube. This was not a problem that I thought I would be able to solve at the beginning of this project.

This will likely be the last log of the OpenFluidWarmer project. I had a lot of fun pushing the boundaries of open-source medical device development and developing a working IV fluid warmer prototype. A big thanks to everyone who provided feedback and encouragement on this project over the last six months. Please feel free to message me if you have any interest in the continued development of the OpenFluidWarmer or want to chat about the challenges of open-source IV fluid warming.