mneuman,
Unfortunately the device does not have an idle mode. Once plugged in it will draw ~6W regardless of whether is it making a measurement or not. The only way to reduce power consumption is to unplug the unit. The 50C idle temps will not hurt the unit, but I understand it may be undesirable for other reasons. If you want it to be unpowered while not in use, consider a powered hub you could also keep on your desktop. Some hubs have buttons that allow you to turn off that port.
Regards,
Andrew