The GrowBoss probes need to be maintained in order to sustain accurate readings. Some common practices we recommend is to clean the probes once every 2 weeks with some distilled water and a Q-tip. Try not to keep the probes submersed in a nutrient solution for too long or else salts will accumulate inside the probe. It's recommended to calibrate the GrowBoss every 3-4 weeks.
If you need help with your GrowBoss you can contact Nutradip HERE