Just used at-home Doppler at 9.2 weeks - unsafe??

I couldnt hear anything because its too early but I did see the machine go from

120 (presumably my heartbeat) to 180 (which was the heart rate of the baby last week).

I just read these can be damaging to the fetus - I only used mine for about 15/20 mins and don’t plan to use it again. Has anyone else had experience with this?