INSTRUCTION MANUAL
Model 407445
Heavy Duty Hygro-Thermometer
Introduction
Congratulations on your purchase of Extech’s Heavy Duty Hygro-Thermometer. The Model
407445 displays Temperature & Relative Humidity simultaneously and includes a built-in
PC interface. This professional meter, with proper care, will provide years of safe reliable
service.
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Model 407445 Version 2.2 February 2004
Specifications
General Specifications
Display
Measurement
Data Hold
Sensor types
Memory Recall
Power off
Data Output
Sampling Time
Operating
Temperature
Operating Humidity
Power Supply
Power Consumption
Weight
Size
Dual function LCD display with contrast adjustment
Relative Humidity (RH) and Temperature (°C & °F)
Freezes Display
Humidity: Thin film, capacitance sensor
Temperature: Thermistor
Records/Recalls MAX, MIN, and Average readings
Automatic power off after approx 10 minutes of inactivity
RS 232 PC serial interface
Approximately 0.8 seconds
Instrument: 32 to 122°F (0 to 50 °C)
Probe: 32 to 140°F (0 to 60°C)
< 90% RH
9V battery
Approx. 8.5 mA DC
0.76 lbs. (345 g) including batteries & probe
Instrument: 7.1 x 2.8 x 1.3" (180 x 72 x 32mm)
Sensor head: 1” diameter x 6.3” (26mm x 160mm)
Range Specifications
Range
RH
10% to 95%
RH
Resolution
0.1% RH
0.1
ο
F/C
Accuracy
> 70% RH: ± 4% RH
< 70% RH: ± 3% RH
± 1.5
ο
F (± 0.8
ο
C)
Temperature 32
ο
F to 122
ο
F
(0
ο
C to 50
ο
C)
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Model 407445 Version 2.2 February 2004
Meter Description
1.
2.
3.
4.
5.
6.
7.
8.
Sensor input
RS-232 serial output jack
LCD Display
Keypad
Sensor
LCD contrast adjustment
Protective rubber jacket
Battery compartment and calibration pots on rear
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Model 407445 Version 2.2 February 2004
Meter Operation
Getting Started
1.
2.
3.
4.
Plug the sensor into the sensor jack at the top of the meter.
Press the Power OFF/ON key to turn the instrument on or off.
Select the temperature units by pressing the °C/°F key. The display will indicate "°C"
or "°F" as selected.
The meter will now display the per cent relative humidity and the temperature.
NOTE:
For accurate relative humidity measurements the meter should be allowed
several minutes to adjust to ambient temperature changes.
Data Hold
Press the Data Hold key to freeze the displayed temperature and humidity readings. The
HOLD icon will appear on the display in the Data Hold mode. Press the Data Hold key
again to exit the Data Hold mode.
MAX, MIN, and AVG Record / Recall
1. Press the RECORD key to begin. The REC indicator will appear on the display and the
meter will begin tracking the highest (MAX), lowest (MIN), and average (AVG)
readings.
2. Press the RECALL key to display the highest (MAX) reading. The MAX indicator along
with the maximum reading recorded since RECORD was first pressed will appear.
3. Press the RECALL key again to view the lowest (MIN) reading.
4. Press the RECALL key again to view the average reading (AVG).
5. To exit, press the RECORD key.
Measurement Considerations
1. The meter includes an Auto Power OFF feature that turns the instrument off after
approximately 10 minutes of inactivity. To disable this feature, press the RECORD key
to enable the MIN/MAX/AVG function.
2. It may be necessary to adjust the display contrast due to a change in viewing angle or
voltage drift. Use the LCD contrast adjustment located on the right side of the meter.
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Model 407445 Version 2.2 February 2004
RS-232 Serial PC Interface
This instrument includes a built-in RS-232 serial data port. This interface is intended for
use with the Extech Data Acquisition Software (PN 407001). For more information, contact
Extech or refer to the manual accompanying the 407001 software package.
Battery Replacement
1. The low battery indicator (LBT) appears on the left corner of the display when the
battery requires replacement. Reliable readings can be obtained for several hours after
the first appearance of the low battery indicator.
2. To replace the battery:
a) Remove the rubber jacket that encases the meter.
b) Open the rear battery compartment using a small coin or screwdriver.
c) Replace the 9V battery and re-assemble the meter.
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Model 407445 Version 2.2 February 2004
PCB Design
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