From the manufacturer

testo 416 Vane Anemometer

• Permanently connected telescopic sensor – maximum length 890 mm, diameter 16 mm
• Airflow measurements, selective and time mean values for calculating air volume
• Hold function; min/max display; auto power off
• Calibration certificate and batteries included

testo 425 Compact Thermal Anemometer

• Temperature and flow measurement as well as volumetric flow calculation
• Permanently attached extendible telescopic probe – maximum length 820 mm, diameter 7.5 mm
• With single and multi-point averaging
• Hold function, display of min/max value, Auto-off function

Volume Flow Measuring Range	0 to +99999 m³/h	0 to +440 m³/h	0.1 to 200 m³/h	N/A
Temperature (NTC) Measuring Range	0 to +50°C	0 to +50°C	0 to +50°C	N/A
Accuracy	0.5°C	0.5°C	0.5°C	N/A
Resolution	0.1°C	0.1°C	0.1°C	N/A
Velocity – Vane Measuring Range	+0.3 to +20m/s	+0.3 to +20m/s	+0.3 to +20m/s	N/A	0.6 to 40 m/s
Accuracy	0.1 m/s + 1.5% of mv	0.1 m/s + 1.5% of mv	0.1 m/s + 1.5% of mv	N/A	±(0.2 m/s + 1.5 % of mv)
Operating Temperature	0 to +50°C	0 to +50°C	0 to +50°C	N/A	-20 to +50 °C
Battery Life	50 hours	50 hours	50 hours	N/A	80 h

Type	Thermal Anemometer	Vane Anemometer
Temperature Measuring Range	-20 to +70 °C	-10 to +50 °C
Temperature (NTC) Accuracy	±0.5 °C (0 to +60 °C) ±0.7 °C (Remaining Range)	±0.5 °C
Velocity Measuring Range	(Thermal anemometer) 0 to +20 m/s	(Vane) 0.4 to 20 m/s
Velocity Measuring Range Accuracy	(Thermal anemometer) ±(0.03 m/s + 5 % of mv)	(Vane) ±(0.2 m/s + 2 % of mv)