User Manual
Professional Thermohygrometer
with NIST-Traceable Calibration
Model 20250-21
THE STANDARD IN PRECISION MEASUREMENT
Introduction
The Digi-Sense Professional Thermohygrometer (Model
20250-21) offers fast response and high accuracy.
This heavy-duty meter measures humidity (relative and
absolute), temperature, plus it calculates dew point and
wet bulb. Advanced features include data Hold, Min/Max
readings, and automatic power-off. 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. Carrying case
3. One 9 V battery
4. User manual
5. NIST-traceable calibration report with data
5 Commonwealth Ave
Woburn, MA 01801
Phone 781-665-1400
2
Toll Free 1-800-517-8431
Meter Description
1. Humidity/temperature sensor
2. LCD
3.
Backlight button
4. WBT/DP/°C/°F button (wet bulb, dew point,
temperature units)
5. MAX/MIN button
6.
Power on/off button
7. MODE button (%RH, g/m
8. HOLD button
3
, gr/ft3)
1
2
3
4
5
8
7
6
3
Display Layout
1. Relative humidity unit
2. Absolute humidity unit (grams per cubic meters)
3. Absolute humidity (grains per cubic feet)
4. Humidity displayed reading
5. °C temperature unit
6. °F temperature unit
7. Dew point icon
8. Wet bulb icon
9. Hold icon
10. Minimum reading icon
11. Maximum reading icon
12. Low-battery indication
13. Auto power-off icon
14. Temperature / DP / WB displayed reading
15. Absolute humidity icon
2 3
1
4
15
14
13 12 11 10 9
4
5
6
7
8
Setup and Operation
Power
Press the Power on/off button to turn unit on.
Taking Measurements
1. Hold the probe in the area to be
tested. Allow adequate time for readings to stabilize.
Press the
2.
between humidity measuring units
(shown on top display): %RH, g/m
or gr/ft
3. Press the °C/°F button to toggle
between temperature measuring modes
(shown on bottom display): °C, °F,
Dew Point (DP), or Wet Bulb (WB).
Absolute Humidity Measurements
1.
To select the Absolute Humidity
measurement, press the
button until g/m
abs appears on the screen.
2. Absolute humidity is now shown
in upper display.
MODE button to toggle
3
.
3
(or gr/ft3) and
MODE
3
,
Temperature Measurements
1. To select the temperature
measurement, press the °C/°F
button until the °C or °F icon
appears in the lower right.
2. Temperature is now shown in
lower display.
5
Setup and Operation (continued)
Dew Point Measurements
1. To select the Dew Point measurement,
press the WBT/DP/°C/°F button until the
DP (°C) or DP (°F) icon appears in the
lower right.
2. Dew Point temperature is now
shown in lower display.
Wet Bulb Measurements
1. To select the Wet Bulb measurement,
press the WBT/DP/°C/°F button until the
WB (°C) or WB (°F) icon appears in the
lower right.
2. Wet Bulb temperature is now shown
in lower display.
Data Hold Function
1. Press HOLD button to freeze the dis-
played readings. The HOLD icon appears
on the lower right-hand side of the
screen.
2. Press HOLD button again to return to
normal operation.
6
Viewing the Min and Max Readings
The MIN/MAX mode allows the user to view only
the lowest (MIN) or highest (MAX) reading.
1. Press MAX/MIN button once and the
MIN icon appears on bottom of screen.
The LCD is now displaying the minimum
reading of the selected parameter in the
display. The display will not change until
a lower reading is registered.
2. Press MAX/MIN button again and
the MAX icon appears on bottom of
screen. The LCD is now displaying the
maximum reading of the selected
parameter. The display will not change until a
higher reading is registered.
Press MAX/MIN button again to exit the
3.
MIN/MAX mode.
Note: While powering on the meter each time, it
restarts recording Minimum and Maximum, and the
recordings don’t stop until the meter is turned off.
7
Setup and Operation (continued)
LCD Backlight
Press Backlight button to turn on the backlight. Press again
to turn off the backlight.
Automatic Power-Off
To conserve battery life, the meter automatically turns off
after 10 minutes (indicated by the icon on the screen). To
disable this feature:
1. Turn the meter off.
2. Press and hold the HOLD button while powering on.
“dis AUP” will appear in the display and the Auto
3.
power-off icon will no longer be shown, indicating that
the Auto power
Note that Auto power-off is re-enabled each time the
4.
meter is turned on.
-off feature is disabled.
8
Specifications
Range
Humidity 0 to 100% RH
Absolute humidity
(calculated)
0 to 500 g/m
0 to 218.5 gr/ft
Temperature –22 to 212°F (–30 to 100°C)
Dew point
–22 to 212°F (–30 to 100°C)
(calculated)
Wet bulb
32 to 176°F (0 to 80°C)
(calculated)
Resolution
Humidity 0.1
Temperature 0.1°F/C
Accuracy
Humidity ±2% RH from 40 to 60% RH
±3% RH from 20 to 40% RH and 60 to 80% RH
±4% RH from 0 to 20% RH and 80 to 100% RH
Temperature ±1.8°F (1°C) from –4 to 140°F (–20 to 60°C)
±2.7°F (1.5°C) from –22 to –4°F (–30 to 19°C)
and 140 to 212°F (60 to 100°C)
3
3
9
Specifications (continued)
Display Dual LCD
Response time <15 sec (90% of final value in moving air)
Sensors Humidity: precision capacitance;
Auto power-off
Operating
temperature
Operating humidity <80% RH, noncondensing
Storage temperature –40 to 185°F (–40 to 85°C)
Storage humidity <99% RH, noncondensing
Weight 14 oz (400 g)
Dimensions 11
Power One 9 V battery
Battery life
Temperature: thermistor
Unit shuts off automatically after
10 minutes to preserve battery life
32 to 122°F (0 to 50°C)
7
⁄8" x 3" x 1" (30 x 7.5 x 5 cm)
Typically 48 hrs. Battery life will be reduced
significantly if the backlight is used
continuously.
10
Maintenance, Recalibration, and Repair
Cleaning and Storage
•
The meter should be cleaned with a damp cloth and
mild detergent when necessary. Do not use solvents
or abrasives.
Store the meter in an area with moderate temperature
•
and humidity (refer to the operating and storage range
in the specifications chart earlier in this manual).
Battery Replacement
When the battery power falls low, the Low Battery icon
will appear on the screen. Remove the battery compartment cover on the rear of unit and replace the 9 V battery. Ensure that the compartment cover is securely
closed when finished.
It is recommended that Digi-Sense products are calibrated
annually to ensure proper function and accurate measure-
ments; 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.
11
For Product and Ordering Information, Contact:
1065DGMAN_20250-21 Rev.1
Manual Part No. 00100-71
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