USER GUIDE Large Vane CFM/CMM Anemometer / Psychrometer + CO2 Model AN320
Introduction Congratulations on your purchase of the Extech AN320 Vane Airflow Anemometer Psychrometer + CO2. This instrument measures Air Velocity, Air Flow (volume), Air Temperature, Relative Humidity, Wet Bulb Temperature, Dew Point Temperature, and CO2 (carbon dioxide). The large, easy‐to‐read backlit LCD includes primary and secondary displays plus numerous status indicators. The optional round and square airflow cone adaptors allow for quick air flow (volume) measurements.
Meter Description Meter Description (front) 1. Top line LCD display reading 2. Bottom line LCD display reading 3. U/mode AVG and up arrow button 4. L/mode and down arrow button 5. ON‐OFF (Power) and SET button 6. HOLD, MAX‐MIN, and left arrow (Enter) button 7. Unit of measure symbol for lower display row 8. Unit of measure symbol for upper display row 9. Air Velocity Vane Meter Description (rear) 10. Air temperature, humidity, and CO2 sensors 11. Battery compartment 3 AN320-EU-EN V1.
Brief Keypad Description Press momentarily to switch the meter ON or OFF. Press and hold this button for 2 seconds to enter or exit the Setup mode (refer to Setup mode section for details).
Display Layout 1. Lower Display digits (air volume, temperature, timer, or menu parameter displays) 2. Upper Display digits (air velocity, humidity, CO2, or menu display parameters) 3. Optional Cone attachment icon 4. Units of measure for duct area programming 5. Vane indicator (flashes very briefly on power up) 6. Display HOLD icon 7. MAX mode icon 8. MIN mode icon 9. Recording icon 10. Elapsed Timer icon 11. AVG mode icon 12. Battery status icon 13.
Operation Air Velocity and Air Volume Measurements 1. Switch the meter ON by pressing the POWER button momentarily. The meter will countdown from 30 to 0 as it performs a self‐test. Press the POWER button again to switch the meter OFF. 2. Note that the meter will automatically enter the sleep mode after 20 minutes of inactivity. To disable this feature: with the meter OFF, press and hold the POWER and the U/mode buttons for 2 seconds. The LCD will display 'n' as it switches ON.
Relative Humidity, Wet Bulb/Dew Point Temperature, and CO2 Readings Sensors are built in to the center of the vane (rear of meter) and are used to measure relative humidity, air temperature, and CO2. Wet Bulb and Dew Point temperatures are calculated based on temperature and humidity readings. 1. Press U/mode to scroll to RH (%) or CO2 (ppm) modes. The measured relative humidity or carbon dioxide readings will be displayed on the upper LCD digits as selected. 2.
Timed Average Mode 1. From the normal operating mode, press and hold the U/mode button for 2 seconds to enter the Multi‐Point Average mode first and then press U/mode one more time momentarily to enter the Timed Average Mode (the AVG and the elapsed timer icons will switch ON). 2. Press HOLD to begin recording. The elapsed timer starts (as shown on the upper display digits) and the clock icon flashes on and off. 3. Press U/mode to stop the clock and to calculate the timed average.
P4.0: Altitude Pressure Compensation 5. When in setup mode P4.0, press HOLD to enter the pressure compensation parameter. The LCD will show hPA (unit of measure: hector‐Pascal or millibar) on the lower line and a flashing 4‐digit number (from 700 to 1990; the default is 1013 hPA which is standard pressure) on the upper line. 6. Press U/mode to increase the pressure value and L/mode to decrease it. 7. Press HOLD once more to return to P4.0. 8.
Battery Replacement When appears on the LCD, the AAA batteries must be replaced. The battery cover is located on the back of the meter. 1. Open the rear battery compartment by carefully pulling down on the compartment’s latch. 2. The battery compartment cover should be completely removed before proceeding. 3. Replace the four (4) 1.5V ‘AAA’ batteries ensuring proper polarity. 4. Close the battery compartment before attempting to use the meter.
Specifications Air Velocity Ranges Resolution Accuracy m/s (meters per sec) 0.2 – 30 m/s 0.01 m/s ± (1.5%rdg + 0.3 m/s) fpm (feet per minute) 40 – 5900 fpm 1 fpm ± (1.5% rdg + 59 fpm) Range Resolution Accuracy 0.1%‐99.9%RH 0.1 RH ±3%RH (10‐90%RH) Relative Humidity RH ±5%RH (<10% or >90%) Air Flow Ranges Resolution CMM (cubic meters/min) 0‐99999 m3/min CFM (cubic ft/min) 0‐99999 ft3/min Temperature Ranges 0.1 up to 9999.9 then 1.0 0.1 up to 9999.9 then 1.
Circuit Custom LSI microprocessor Display Dual function 13 mm (0.5") 4‐digit LCD Sampling rate 1 reading per second approx.
Error Messages Error codes and solutions Air Temperature E02: Temperature reading is lower than the low range limit. Place the meter in room temperature for 30 minutes. If E02 continues, send the unit to Extech for repair. E03: Temperature exceeds the high range limit. Place the meter in room temperature for 30 minutes. If E03 continues to appear, send the unit to Extech for repair. E31: The A‐to‐D converter requires replacing. Send the meter to Extech Instruments for repair.
Appendix: Useful Equations and Conversions Area equation for rectangular or square ducts Height (H) Area (A) = Width (W) x Height (H) Width (W) Area equation for circular ducts 2 Area (A) = pi x r 2 Where pi = 3.14 and r = radius x radius Radius Cubic equations 3 2 CFM (ft /min) = Air Velocity (ft/min) x Area (ft ) 3 2 CMM (m /min) = Air Velocity (m/sec) x Area (m ) x 60 NOTE: Measurements made in inches or centimeters must be converted to feet or meters before using these formulae.
