User Manual
THE STANDARD IN PRECISION MEASUREMENT
Professional CFM/CMM
Vane Thermoanemometer
with NIST-Traceable Calibration
Model 20250-15
2
Introduction
The Digi-Sense Professional CFM/CMM Vane Thermoanemometer (Model
20250-15) provides precision air velocity, airflow (volume), and temperature
measurements. The large, easy-to-read backlit LCD includes primary and
secondary displays plus numerous status indicators. The meter features
16 memory locations (8 for CFM and 8 for CMM) to store and recall commonly
used area sizes. The instrument is fully tested and calibrated to NIST-traceable
standards. Careful use of this meter will provide years of reliable service.
Unpacking
Check individual parts against the list of items below. If anything is missing
or damaged, please contact your instrument supplier immediately.
1. Meter
2. Anemometer vane sensor on 3.9 ft (120 cm) cable
3. Hard carrying case
4. One 9 V battery
5. User manual
6. NIST-traceable calibration report with data
Meter Description
1. LCD
2. Vane sensor
3. Temperature buttons
4. Power On/Off button
5. Airflow/velocity buttons
6. AVG
7. Backlight
1
7
6
5
2
3
4
3
Keypad
• POWER Press to turn the meter
ON or OFF
• MAX/MIN Used to record and store
the highest, lowest and average airflow or velocity readings.
(LEFT) also serves as change decimal point button in AREA mode
• UNITS Press to select the mode of
operation. In FLOW mode, the meter
displays air volume. In VELOCITY
mode, the meter displays air speed.
(UP) also serves as increase number button in AREA mode.
• AVG Used to Average multiple read-
ings in FLOW or VELOCITY mode.
Up to 20 readings can be averaged.
• HOLD Press to freeze the displayed
reading. Press again to unlock display. This button also functions as
the (RIGHT) scroll button in AREA
mode.
• AREA/ NEXT Press and hold to
manually enter the area of a duct in
CFM or CMM mode. In AREA mode,
used to select memory locations 1
through 8.
•
Press to turn the backlight on/off
• MAX/MIN (Temperature) Used to
record and store the highest, lowest
readings for air temperature.
• HOLD (Temperature) Press to freeze
the displayed temperature reading.
Press again to unlock the display.
Press and hold for 3 seconds to
switch between °C and °F. Meter will
beep twice to indicate change.
4
Display Layout
• REC (top of LCD): indicates that min/
max temperature function is running
• MAX (top of LCD): maximum hold
function engaged for an air temperature
measurement
• MIN (top of LCD): minimum hold
function engaged for an air temperature
measurement
• HOLD (top of LCD): data hold function
engaged for an air temperature
measurement
• °C / °F: temperature units of measure
•
: Low-battery indicator
• AREA (ft
2
, m2): units for area dimensions
• VEL: indicates that meter is in air
velocity mode
• FLOW: indicates that meter is in
airflow mode
• CFM/CMM: airflow units of measure
• m/s, ft/min, km/h, MPH, knots: air
velocity units of measure
• X10, X100: multipliers for airflow
readings
• REC: indicates that min/max function is
running (top for temp, bottom for air)
• MAX (bottom of LCD): maximum hold
function for an air velocity and airflow
measurement
• MIN (bottom of LCD): minimum hold
function for an air velocity and airflow
measurement
• AVG: air averaging mode
• HOLD (bottom of LCD): Data Hold for an
Air Velocity and Airflow function
Large LCD digits at bottom of display
for air velocity and airflow
Smaller LCD digits at top right of display
for probe temperature
5
Setup and Operation
Connecting the Vane
1. The vane plug is inserted in meter’s sensor jack at the top of meter. The
plug and jack are keyed so that the plug can only fit in the jack one way.
2. Turn the plug carefully until it lines up with the jack and then firmly push
into place. Do not apply undue force or try to twist the plug side-to-side.
3. If the vane is not connected to the meter properly or if the sensor is
defective, the LCD will indicate OL in place of a Temperature reading.
Air Velocity Measurements (Single Point)
1. Turn on the meter using the On/Off button.
2. Press UNITS button to select the desired
unit of measure. Note: At power-up the
meter will display the last unit of measure
previously entered.
3. Place the sensor in the air stream. Ensure
that the air enters the vane as indicated by
the arrow sticker placed inside the vane.
4. View the readings on the LCD. The large
main bottom display shows the air velocity
reading. The upper right subdisplay shows
the temperature reading.
Air Velocity Measurement Averaging Mode
1. To enter 20 point averaging mode, press
and hold the AVG button until it beeps
twice. The AVG icon will be displayed.
2. Take a measurement and press the AVG button. A single beep will sound
and the HOLD icon will appear briefly in the display.
3. The average reading will be displayed and number of readings measured
will appear in the upper right-hand corner of the display. After 5 seconds,
the display will return to the current reading.
4. Repeat steps 2–3 until the desired number of points have been measured.
5. To return to standard velocity measuring mode, press and
hold AVG button until meter beeps twice.
Note: In the standard velocity measuring mode, press the AVG button once
to recall the previous average. The average will be cleared when you enter
the averaging mode again.
Side view of Vane
Arrow
Airflow
6
Setup and Operation (continued)
Airflow Measurements (CFM / CMM)
1. Turn on the meter using the On/Off button.
2. Press the UNITS button to select the desired airflow units: CFM (cubic feet
per minute) or CMM (cubic meters per minute). Note: At power-up the
meter will display the last unit of measure previously entered.
3. To begin entering the area in ft
2
or m2, press and hold the AREA button until
it beeps twice. The leftmost digit of the bottom display will begin to flash.
4. Use the (UP) button to change the flashing digit.
Use the (LEFT) button to move the decimal.
Use (RIGHT) button to select the other digits.
5. After all of the digits are entered, press and hold the AREA button (until
meter beeps twice) to save the area into memory and return to CFM or
CMM measuring mode.
6. Place the sensor in the air stream. Ensure that the
air enters the vane as indicated by the arrow sticker
placed inside the vane. Refer to the diagram. The
large main bottom LCD display shows the airflow
reading. The upper right LCD subdisplay shows the
temperature reading.
The meter has 16 memory locations (8 for CFM and
8 for CMM) that can be used to store commonly used
area sizes that you can recall at any time.
1. Press the AREA button until meter beeps twice. A
memory location number will appear in the top right
of the display indicating the memory location.
2. Push the NEXT button to scroll through and select the
desired location. Once you have selected the desired
memory location enter your dimension:
Use the (UP) button to change the flashing digit
Use the (LEFT) button to move the decimal
Use (RIGHT) button to select the other digits.
3. After all of the digits are entered, press and hold the AREA button (until it
beeps twice) to save the area into memory and return to CFM or
CMM measuring mode.
To select and use a previously stored dimension, press and hold the AREA
button until it beeps twice.
1. Press NEXT to scroll through the 8 memory locations. Press and hold the
AREA button until it beeps twice to return to CFM or CMM measuring mode.
Side view of Vane
Arrow
Airflow
7
Airflow Averaging Mode
1. To enter the 20-Point Averaging Mode, press and hold the AVG button
until it beeps twice. The AVG icon will be displayed.
2. Take a measurement and press the AVG button. A single beep will sound
and the HOLD icon will appear briefly in the display.
3. The average reading will be displayed and number of readings measured
will appear in the upper right-hand corner of the display. After 5 seconds,
the display will return to the current reading.
4. Repeat steps 2–3 until the desired number of points have been measured.
5. To return to standard airflow measuring mode, press and hold
AVG button until meter beeps twice.
Note: In the standard velocity measuring mode, press the AVG button once
to recall the previous average. The average will be cleared when you enter
the averaging mode again.
Data Hold (Air Velocity/Airflow)
1. While taking measurements, press the HOLD button to freeze the
air velocity/airflow reading.
2. The HOLD indicator will appear in the bottom of the LCD.
3. Press the HOLD button again to return to normal operation.
MAX/MIN/AVG Record (Air Velocity/Airflow)
This allows the user to record and view the highest (MAX), lowest (MIN),
and average (AVG) readings.
1. Press MAX/MIN button. The MAX indicator and RECORD indicator along
with the maximum reading will appear on the LCD and the meter will
begin keeping track of the MAX, MIN and Average values.
2. Press the MAX/MIN button again to view the minimum reading. The MIN
indicator along with the minimum reading will appear on the LCD.
3. Press the MAX/MIN button again to view the average reading. The AVG
indicator along with the average reading will appear on the LCD.
Note: Average recording will stop automatically after 2 hours, and the
upper LCD subdisplay will show OFF (only in the average mode).
4. Press the MAX/MIN button again to display current readings. Note: Meter
will keep recording MAX/MIN/AVG readings.
5. To clear and stop MAX/MIN/AVG recording and return to normal opera-
tion, press and hold the MAX/MIN button until the meter beeps twice.
8
Setup and Operation (continued)
Automatic Power-Off
To conserve battery life, the meter automatically turns off after 20 minutes.
To disable this feature:
1. Turn the meter OFF.
2. Press and hold the Backlight button while turning the meter on.
3. “dis APO” will appear in the display. The Auto power-off feature will now
be disabled.
4. Note that Auto power-off is re-enabled each time the meter is turned on.
5. Also note that Auto power-off is disabled in CFM/CMM or average mode.
Battery Replacement
When the low-battery icon appears on the LCD, the 9 V battery must be
replaced.
1. Disconnect the sensor.
2. Remove the meter’s battery cover.
3. Replace the 9 V battery.
4. Close the battery compartment cover.
9
Specifications
Air velocity Range Resolution Accuracy
m/s (meters per sec) 0.40 to 30.00 m/s 0.01 m/s ±(3% + 0.20 m/s)
ft/min (feet per minute) 80 to 5900 ft/min 1 ft/min ±(3% + 40 ft/m)
km/h (kilometers per hour) 1.4 to 108.0 km/h 0.1 km/h ±(3% + 0.8 km/h)
MPH (miles per hour) 0.9 to 67.0 MPH 0.1 MPH ±(3% + 0.4 MPH)
knots (nautical MPH) 0.8 to 58.0 knots 0.1 knots ±(3% + 0.4 knots)
Airflow Range Resolution Area
CFM (cubic feet per min)
0 to 999,900 ft
3
/min
0.001 to 100
0.000 to 999.9 ft
2
CMM (cubic meters per min)
0 to 999,900 m
3
/min
0.001 to 100
0 .000 to 999.9 m
2
Air temperature Range Resolution Accuracy
14 to 140°F (–10 to 60°C) 0.1°F/C 4.0°F (2.0°C)
Circuit Custom LSI microprocessor circuit
Display Dual-function 16 mm 4-digit LCD
Sampling rate Approximately 1 reading per second
Sensors Air velocity/flow sensor: Conventional angled vane arms with low-
friction ball bearing
Temperature sensor: NTC-type precision thermistor
Automatic power-off Unit shuts off automatically after 20 minutes to preserve battery life
Operating temperature 32 to 122°F (0 to 50°C)
Operating humidity <80% RH, noncondensing
Storage temperature 14 to 140°F (–10 to 60°C)
Storage humidity <80% RH, noncondensing
Weight 1.6 lb (725 g) including battery and probe
Dimensions Main instrument: 8" x 3" x 2" (20.3 x 7.5 x 5 cm)
Vane sensor head: 2
3
⁄4" (7 cm) diameter
Cable length: 3.9 ft (1.2 m)
Power One 9 V battery
Battery life Typically 80 hrs. Battery life will be reduced significantly if the
backlight is used continuously.
Battery current Approximately 8.3 mA DC
10
11
Manual Part No. 00100-54
1065DGMAN_20250-15 Rev.1
For Product and Ordering Information, Contact:
Maintenance, Recalibration, and Repair
It is recommended that Digi-Sense products are calibrated annually to
ensure proper function and accurate measurements; however, your quality
system or regulatory body may require more frequent calibrations. To schedule
your recalibration, please contact InnoCal, an ISO 17025 calibration laboratory
accredited by A2LA.
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