Extech Instruments 407445 User manual

Page 1 Model 407445 Version 2.2 February 2004
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.

Page 2 Model 407445 Version 2.2 February 2004
Specifications
General Specifications
Display Dual function LCD display with contrast adjustment
Measurement Relative Humidity (RH) and Temperature (°C & °F)
Data Hold Freezes Display
Sensor types Humidity: Thin film, capacitance sensor
Temperature: Thermistor
Memory Recall Records/Recalls MAX, MIN, and Average readings
Power off Automatic power off after approx 10 minutes of inactivity
Data Output RS 232 PC serial interface
Sampling Time Approximately 0.8 seconds
Operating
Temperature Instrument: 32 to 122°F (0 to 50 °C)
Probe: 32 to 140°F (0 to 60°C)
Operating Humidity < 90% RH
Power Supply 9V battery
Power Consumption Approx. 8.5 mA DC
Weight 0.76 lbs. (345 g) including batteries & probe
Size 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 Resolution Accuracy
RH 10% to 95%
RH 0.1% RH >70% RH: ± 4% RH
< 70% RH: ± 3% RH
Temperature 32οF to 122οF
(0οC to 50οC) 0.1ο F/C ± 1.5 οF (± 0.8οC)

Page 3 Model 407445 Version 2.2 February 2004
Meter Description
1. Sensor input
2. RS-232 serial output jack
3. LCD Display
4. Keypad
5. Sensor
6. LCD contrast adjustment
7. Protective rubber jacket
8. Battery compartment and calibration pots on rear

Page 4 Model 407445 Version 2.2 February 2004
Meter Operation
Getting Started
1. Plug the sensor into the sensor jack at the top of the meter.
2. Press the Power OFF/ON key to turn the instrument on or off.
3. Select the temperature units by pressing the °C/°F key. The display will indicate "°C"
or "°F" as selected.
4. 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.

Page 5 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.

Page 6 Model 407445 Version 2.2 February 2004
Calibration
Humidity Calibration
Note: Calibration reference solutions are available from Extech (33%: Part No. 407453 and
75%: Part No. 407465).
1. The grid located on top of the sensor must be removed so that it may fit into the
calibration bottles.
2. Prior to calibrating, allow the meter and probe to stabilize to room temperature.
3. Open the battery compartment to access the calibration adjustments (see diagram
below).
4. Place the sensor head into the 33% calibration reference solution. Wait for a stable
reading (up to 30 minutes). Adjust VR3 until the display reads 33.0%.
5. Place the sensor head into the 75% calibration reference solution. Wait for a stable
reading (up to 30 minutes). Adjust VR4 until the display reads 75.0%.
Temperature Calibration
Note that the temperature calibration adjustments are rarely required. However if a
temperature calibration is in order, the user must have access to an environmental
chamber capable of providing 21oC and 50oC conditions. Allow time for the chamber and
the meter sensor to stabilize (30 minutes approx.) and then adjust the appropriate
potentiometer (see below):
•VR7 - Temperature 21oC adjustment
•VR6 - Temperature 50oC adjustment

Page 7 Model 407445 Version 2.2 February 2004
Calibration and Repair Services
Extech offers repair and calibration services for the products we sell. Extech also
provides NIST certification for most products. Call the Customer Service Department for
information on calibration services available for this product. Extech recommends that
annual calibrations be performed to verify meter performance and accuracy.

Page 8 Model 407445 Version 2.2 February 2004

Support line [phone]
Technical support: Extension 200; E-mail: [email protected]m
Repair & Returns: Extension 210; E-mail: [email protected]
Product specifications subject to change without notice
For the latest version of this User’s Guide, Software updates, and other
up-to-the-minute product information, visit our website: www.extech.com
Extech Instruments Corporation, 285 Bear Hill Rd., Waltham, MA 02451
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects
in parts and workmanship for one year from date of shipment (a six month limited warranty
applies to sensors and cables). If it should become necessary to return the instrument for
service during or beyond the warranty period, contact the Customer Service Department at
[phone] ext. 210 for authorization or visit our website www.extech.com for contact
information. A Return Authorization (RA) number must be issued before any product is
returned to Extech. The sender is responsible for shipping charges, freight, insurance and
proper packaging to prevent damage in transit. This warranty does not apply to defects
resulting from action of the user such as misuse, improper wiring, operation outside of
specification, improper maintenance or repair, or unauthorized modification. Extech
specifically disclaims any implied warranties or merchantability or fitness for a specific
purpose and will not be liable for any direct, indirect, incidental or consequential damages.
Extech's total liability is limited to repair or replacement of the product. The warranty set
forth above is inclusive and no other warranty, whether written or oral, is expressed or
implied.
Copyright ©2005 Extech Instruments Corporation.
All rights reserved including the right of reproduction in whole or in part in any form.