BBT charting

Hi ladies! I've been using my regular thermometer for charting and I've just gone out and purchased a real basal thermometer. I'm 11 dpo and 6 days till AF is due. Should I keep using regularly thermometer until new cycle or is it ok to start using my new one? My old one only records to 1/10th of temp while new one does it to 1/100th. TIA