The Amprobe TR300's Alarm only works when powered by an external power supply

The Amprobe TR300 Temperature and Relative Humidity Data Logger has two ways of being powered: 4 AA alkaline batteries, or an external DC power supply.

The when the alarm function is set up, it is important to note that the audible sound will only play if the TR300 is being powered by an external power supply, and will NOT play if it is on battery power.

A DC power supply is not provided with the device, and neither Fluke nor Amprobe are able to provide one to a user. Instead, the user will need to source their own power supply option. The required specifactions are 9V DC, center pin positive, 500mA minimum.