Esperanza pulse oximeter makes it fast, safe and painless to observe your health anywhere and whenever you want. Clip it to your finger and wait for 3 seconds you will get the data. Supply voltage: 3V Operating current: ≤40mA SpO2 parameter: Measuring range: 35% - 100%  Accuracy: 70% - 100% ± 3% Pulse rate: Measuring range: 30bpm - 240bpm Parameter accuracy: ± 2bpm or ± 2% Operation temperature: 41°F - 104°F (5°C - 40°C) Environment humidity: 30% - 80% Pressure: 70kPa - 106kPa Performance under low perfusion condition : Same with modulation amplitude as low as 0.2% Resistance to light interference: ± 1% Resistance to 50Hz/60Hz interference: Precise Power supply: 2 x AAA batteries 1.5V (not included in package)