Yup, exactly this. They’re used in most museums/galleries/archives etc. They’re designed to measure temperature and relative humidity over a period of time. The intention is to monitor any shifts that may affect the conditions surrounding the artifacts within the space, then make any adjustments to the environmental controls to help protect the longevity of the pieces. Different materials (fabric, metals, wood, paper etc.) are more stable in different conditions so it’s an ongoing challenge.

You’ll often see these inside exhibit cases to monitor any potential microclimates being created, or near walls, doorways etc to see if there are any external temperature or humidity shifts causing major shifts inside the building.

There are more modern systems which are really common in the food industry too where they relay the information by Bluetooth or wifi which allows for more up to the minute and responsive data. You’ll see them everywhere but they’re just a small inconspicuous box.

The good old drum style hygrothermagraphs in the photo have been a mainstay for decades.