Meter Instruction Manual

INSPECTUSA DAFM3B Digital Air Flow Meter Instruction Manual


The DAFM3B Anemometer/Psychrometer is designed with 6 HVAC/R parameters in one instrument. These are included in a portable, battery-operated instrument for measuring humidity, air temperature, dew point, wet bulb, air velocity and air volume. The vane probe includes sensors for velocity, temperature and humidity.


  • Measures Air Velocity, Temperature, and Relative Humidity (RH%)
  • Calculates Wet-bulb temperature, dew point, and air volume (CFM, CMM)
  • 3″ diameter air vane
  • Timed accumulative average for air volume with one hour maximum
  • Min/Max and Hold
  • English/Metric Scales
  • Fast response
  • Auto-power off (can be disabled)
  • Low battery indicator


  • DAFM3B Meter
  • Air vane probe
  • Battery (1 x 9V)
  • User manual
  • Hard carrying case


Before using this meter, read all safety information carefully. In this manual the word “WARNING” is used to indicate conditions or actions that may pose physical hazards to the user. The word “CAUTION” is used to indicate conditions or actions that may damage the instrument.

⚠ CAUTION! Do not strike the fan portion of the probe.


INSPECTUSA DAFM3B Digital Air Flow Meter Instruction Manual - CONTROLS AND INDICATORS

  1.  On/Off (Setup): Press briefly to power meter on. Press and hold to turn the meter off. · Note: When the meter is OFF, press more than two seconds to enter SETUP mode.
  2. HOLD: Freezes display reading for current parameter
  3. MODE: Press to scroll through available measurements of
    velocity, air flow, ambient temperature, relative humidity, wet-bulb temperature, and dew point temperature.
  4. EXIT: Use to exit setup. · Note: Press and hold to exit timed average display
  5. START/STOP: Press to begin air volume timed average. Press a second time to pause timed average.
  6. LW-D-AREA: Press when setting up area for calculation of air volume. Pressing repeatedly scrolls through the three options. (LW-Length/Width, D-Diameter, A ­ Area)
  7. MIN/MAX AVG ( ): Press to display minimum or maximum values for any measurement. Press when in timed average air volume to display average, minimum or maximum air volume.


INSPECTUSA DAFM3B Digital Air Flow Meter Instruction Manual - FIGURES AND COMPONENTS



With the meter off, press and hold ON/OFF and HOLD for more than two seconds. The display will show an “n” indicating that auto power off is disabled.


  • With the meter off press and hold ON/OFF (Set) button for more than two seconds.
  • Press MIN/MAX AVG ( ) to select unit (P10)
  • Press or to switch units
  • Press MIN/MAX AVG ( ) to select choice
  • Press EXIT to return to normal operation


When the DAFM3B is first powered on, air velocity is the default display. To view other parameters press “MODE” key. Each parameter will be displayed in turn.

  • VEL ­ Air Velocity
  • VOL ­ Air volume in CFM or CMM, based on dimensions entered Note: Icon at bottom of screen will indicate the method used to calculate volume (LW-Length/Width, D-Diameter, A ­ Area).
  • TA ­ Ambient Temperature measured at the probe tip
  • RH ­ Relative Humidity measured at the probe tip
  • WBT ­ Wet Bulb Temperature calculated from measured temperature and RH%
  • DP ­ Dew Point Temperature calculated from measured temperature and humidity


Measuring air volume with the DAFM3B has two steps. The first step is to enter the characteristics of the area being measured. There are three methods to enter this and depend on the location of your measurement. If measuring square duct work you would enter Length and Width (LW). For round duct you would enter Diameter (D). If measuring the exit with a grill it is recommended to use the effective area or free area (A) from the grill manufacture. If this is not known, the air volume measurement will be an estimate.
Note: Grill manufacturers often provide engineering data on effective or free area. This is indicated as the Ak value.


  1. Press MODE until VOL is showing in the upper right corner of the display
  2. Press LW-D-AREA until the desired method is showing in the lower left corner of the display
  3. Press MIN/MAX AVG ( ) to select this mode
    a. Press (HOLD) to increase the value
    b. Press (LW-D-AREA) to decrease the value
    c. Press MIN/MAX AVG ( ) to accept the displayed value
    Note: Press and hold to scroll through the values quickly. Release and then press briefly to increase or decrease one digit at a time.

After entering the duct characteristics you will be taken back to the display for Air Volume. Hold the probe in the area to be measured for a direct display of air volume.


  1. Press MODE until VOL is showing in the upper right corner of the display
  2. Enter duct dimensions using the method described prior section
  3. Place the probe at the face of the opening, or on the grill surface
  4. Press “START” to begin timed average
    a. Slowly move the probe across the entire surface of the grill or duct opening
  5. Press “STOP” to end timed average. a. The cumulative timer will stop when the DAFM3B is not capturing data
  6. Press MIN/MAX AVG ( ) after capturing data to view average volume
    a. AVG flashing and elapsed time will show when displaying average
    b. AVG flashing, elapsed time and MIN will show minimum measured volume
    c. AVG flashing, elapsed time, and MAX will show maximum measured volume
  7.  Press and hold EXIT to end test


To obtain air volume on a grill with unknown effective or free area you must estimate the free area. This is difficult, but can be used to provide an estimate of the volume for comparison testing. If multiple grills of the same design are compared using this method, you will have an accurate relative comparison, although the actual value may not be exact.

Method 1

  • Measure length and width in inches.
  • Obtain overall area in square inches by multiplying length times width.
  • Divide square inches by 144 to convert to square feet.
  • Multiply the result by 0.70 (70%) to estimate the actual open area.

Note: For return registers that are more open, increase the factor to 0.9 (90% open). For louvered registers with much more covered area decrease to 0.5 or 0.6 (50~60% open).

Example ­ 4″x10″ residential floor register

  • Step 1 ­ 4″ and 10″
  • Step 2 ­ 4 x 10 = 40 square inches
  • Step 3 ­ 40 ÷ 144 = 0.2777 square feet
  • Step 4 ­ 0.277 x 0.70 = 0.194 square feet (use this when entering free area “A” on the DAFM3B)

Method 2
Measure the grill area inside the frame of the register, calculate area in square inches and convert to square feet using the method 1 steps. You do not need to perform step 4.

Example ­ 4″x10″ floor register

  • Step 1 ­ actual louver area dimensions are 9″ x 3.5″
  • Step 2 ­ 9 x 3.5 = 31.5 square inches
  • Step 3 ­ 31.5 ÷ 144 = .219 square feet

Note: This method may result in a slightly elevated result as it does not fully remove the louvers that are in the air path.



When the low battery ” ” icon appears on the display, all readings will change to ” ” to prevent inaccurate results. Change the 9V battery located in the inner compartment on the rear of the instrument.


Periodically clean your meters case using a damp cloth (not wet) only. DO NOT use abrasive, flammable liquids, cleaning solvents, or strong detergents as they may damage the finish, impair safety, or affect the reliability of the structural components.


Remove screw from the battery compartment cover on the back of your meter and remove cover. Replace battery with a fresh 9 Volt battery paying attention to polarity. Replace cover and secure with screw.


Air velocity range99 ~ 3937 ft/min0.5 ~ 20 m/s
Air velocity resolution0.1 ft/min0.1 m/s
Air velocity accuracy±5%±5%
Temperature range-4 ~ 140°F-20 ~ 60°C
Temperature resolution0.1°F0.1°C
Temperature accuracy±1˚F±0.6˚C
RH% range0.1 ~ 99.9% RH
RH% resolution0.1% RH
RH% accuracy±3% (10 ~ 60% RH);

±5% at others

Wet bulb range-7.6 ~ 158 °F-22 ~ 70°C
Wet bulb resolution0.1°F0.1°C
Air volume display0 ~ 99999 CFM (m3/s)
Air volume resolution0.1 (0 ~ 9999.9), 1 (10000 ~ 99999)
Dew point range-90˚ ~ 158˚F (-68˚ ~ 70˚C)
Dew point resolution0.1˚F (0.1˚C)
Dew point accuracy±3% (-10 ~ 60% RH);

±5% at other range

LCD Size (HxW)1.38 x 2.13 inches35.2 x 54 mm
Operating temperature range32 ~ 122°F0 ~ 50°C
Operating RH%Less than 80% (handset)
Storage temperature range-4 ~ 122°F-20 ~ 50°C
Storage RH%Less than 90%
Dimension7.1 x 2.9 x .5 inches180 x 73 x 38 mm
Weight.37 lbs170g
Battery9V battery (1)

Limited Warranty

The DAFM3B is warranted to be free from defects in materials and workmanship for a period of one year from the date of purchase. If within the warranty period your instrument should become inoperative from such defects, the unit will be repaired or replaced at UEi’s option. This warranty covers normal use and does not cover damage which occurs in shipment or failure which results from alteration, tampering, accident, misuse, abuse, neglect or improper maintenance. Batteries and consequential damage resulting from failed batteries are not covered by warranty.

Any implied warranties, including but not limited to implied warranties of merchantability and fitness for a particular purpose, are limited to the express warranty. UEi shall not be liable for loss of use of the instrument or other incidental or consequential damages, expenses, or economic loss, or for any claim or claims for such damage, expenses or economic loss.

A purchase receipt or other proof of original purchase date will be required before warranty repairs will be rendered. Instruments out of warranty will be repaired (when repairable) for a service charge.

For more information on warranty and service:

1-800-547-5740 · FAX: (503) 643-6322 · Email: [email protected]

This warranty gives you specific legal rights. You may also have other rights which vary from state to state.

Copyright © 2014 UEi. All Rights Reserved


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