General EP8709 User manual
TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . 2 –4
Key Features . . . . . . . . . . . . . . . . . . . . 4
What’s in the Box . . . . . . . . . . . . . . . . 4
Product Overview . . . . . . . . . . . . . 4 –6
Setup Instructions . . . . . . . . . . . . . . . . 7
Install Battery . . . . . . . . . . . . . . . . . . 7
Operatin Instructions . . . . . . . . 7 – 10
Makin Basic Measurements . . . 7 –9
Trackin Min and Max Levels . . 9 – 10
Calibratin the Meter . . . . . . . . 10 – 12
Specifications . . . . . . . . . . . . . . . . . . 13
Operatin & Maintenance Tips . . . . . 14
Warranty Information . . . . . . . . . . . . 15
Return for Repair Policy . . . . . . . . . . 16
INTRODUCTION
Thank you for purchasing General Tools &
nstruments’ EP8709 Calibratable 4-Function
Thermo-Hygrometer. Please read this user’s
manual carefully and thoroughly before
using the instrument.
The EP8709 can measure any
environment’s ambient temperature,
relative humidity (RH), and dew point and
wet bulb temperatures. These
measurements are typically made by three
groups of users:
2
• Water damage restoration contractors
• HVAC/R system installers and technicians
• Professionals charged with monitoring
and maintaining the environment of
facilities such as office buildings,
greenhouses, food and equipment storage
facilities, wineries, freezers, shipping
containers, computer rooms, labs,
libraries, museums and saunas.
The dew point is the temperature below
which the water vapor in a volume of air at
a given constant barometric pressure will
condense into liquid water at the same rate
at which it evaporates. Condensed water is
called dew when it forms on a solid surface.
Another way to think of the dew point is as
an air saturation temperature associated
with relative humidity (RH). A high RH value
indicates that the dew point is close to the
current ambient air temperature. At 100%
RH, the dew point temperature is equal to
the ambient temperature because the air is
completely saturated with water.
The wet bulb temperature is the
temperature that a volume of air would
have if it were cooled to saturation (100%
RH) by the evaporation of water into it, with
the latent heat coming from the volume of
air. t is the lowest temperature that can be
reached under current ambient conditions
by the evaporation of water only. The wet
3
bulb temperature is the temperature you
feel when your skin is wet and exposed to
moving air as opposed to the actual air
temperature—the dry bulb temperature.
The EP8709 is powered by one “9V” battery
(included).
KEY FEATURES
• Jumbo backlit display with 2-line readout
• Field calibratable using optional 33% and
75% salts
• Data hold and Min/Max functions
• °F/°C switch
• 20-minute Auto Power Off function
• Low battery indicator
WHAT’S IN THE BOX
The EP8709 comes fully assembled in a box
along with a sensor protection cap, a “9V”
battery and this user’s manual.
PRODUCT OVERVIEW
Figure 1 shows all of the controls, indicators
and physical structures on the front, top and
bottom of the EP8709. Figure 2 shows all
text and icons that could appear on the
unit’s LCD. Familiarize yourself with the
positions and functions of all buttons,
structures and icons before moving on to
the Setup nstructions and Operating
nstructions.
4
Fig. 1. The EP8709’s controls, indicators
and physical structures
A. Humidity and temperature sensors
B. LCD
C. (Power on/off) button
D.
F/C
button
E.
WBT
(wet bulb temperature) button
F.
DEW
button
G.
HOLD
button
H.
MAX/MIN
button
. Battery compartment
5
A
B
C
D
I
F
G
H
E
Fig. 2. All possi le display indications and
their meanings
A. Low battery icon
B. Data hold indicator
C. Maximum reading indicator
D. Minimum reading indicator
E. °C indicator
F. °F indicator
G. Wet bulb temperature indicator
H. Dew point temperature indicator
. Temperature readout
J. Relative humidity (RH) readout
6
A
B
C
D
J
H
G
I
E
F
SETUP INSTRUCTIONS
INSTALL BATTERY
1. The meter’s battery compartment (Fig. 1,
Callout ) is accessible from the bottom of
the unit. Use a Phillips-head screwdriver
to loosen the single screw in the back of
the unit that holds the yellow battery
compartment cover in place. Set the
cover and screw aside.
2. Plug the included “9V” battery into the
wired socket inside the compartment. The
terminals of the battery and the socket
mate in only one way, with the smaller
male terminal plugging into the larger
female terminal.
3. Replace the battery compartment cover
and tighten the screw to secure it to the
housing.
OPERATING
INSTRUCTIONS
MAKING BASIC
MEASUREMENTS
Before making any measurements, rotate
the sensor protection cap with your thumb
and index finger so its three vents are open
to the ambient environment from both the
front and back. Press the button to
power on the meter. The dual displays will
7
immediately begin reading out humidity and
ambient temperature measurements made
by the sensors at the top of the unit.
To display the dew point temperature
(instead of ambient temperature) on the lower
readout, press the
DEW
button. The reading
will be accompanied by the symbol
DEW
at
its left. To return to displaying ambient
temperature, press the
DEW
button again.
To display the wet ul temperature
(instead of ambient temperature) on the
lower readout, press the
WBT
button. The
reading will be accompanied by the symbol
WBT
at its left. To return to displaying
ambient temperature, press the
WBT
button
again.
By default, the EP8709 displays ambient,
dew point and wet bulb temperatures in °F.
To switch to °C
, press the
F/C
button.
To hold a pair of readings (RH + ambient/
dew point/wet bulb temperature), press the
HOLD
button. The text
HOLD
will appear at
the right of the RH readout. To “unfreeze”
the display and resume showing real-time
readings, press the
HOLD
button again. This
will cause
HOLD
to disappear from the RH
readout.
Pressing any button turns on the green
backlight for 10 seconds.
To extend the life of the “9V” battery
powering the EP8709, the unit’s Auto Power
8
Off (APO) function will automatically shut
down the instrument if no front-panel
buttons are pressed within any 20-minute
period.
To disa le the APO function
, power
on the unit in a special way by pressing and
holding the
DEW
button while pressing the
button. The LCD will confirm that you
are disabling the APO function by displaying
its complete set of icons (see Fig. 2) until
you release the
DEW
button. The APO
function will be enabled the next time you
power on the unit in the normal way.
To power off the EP8709
, press and hold
the button for at least 3 seconds.
TRACKING MIN AND MAX LEVELS
After being powered on, the EP8709
automatically operates in “Recording” mode
for the purpose of tracking maximum and
minimum RH and ambient temperature
values over the duration of a measurement
“session”.
To display the maximum RH and am ient
temperature
values measured during the
current measurement session, press the
MAX/MIN
button once. The text
MAX
will
appear at the right of the RH readout and
both readouts will indicate the highest
values (of RH and ambient temperature)
measured since 1) the meter was last
powered on, or 2) the Min/Max memory
was reset (by entering and exiting Min/Max
mode.)
9
To display the minimum RH and am ient
temperature
values measured since the
meter was powered on, press the
MAX/MIN
button again. The text
MIN
will replace
MAX
at the right of the RH readout and both
readouts will indicate the lowest values
(of RH and ambient temperature) measured
during the current session.
To return to displaying real-time RH and
ambient temperature readings, press the
MAX/MIN
button a third time. The text
MIN
will disappear from the RH readout. Exiting
Min/Max mode clears the Min/Max memory
and begins a new measurement session.
CALIBRATING THE METER
Your EP8709 was calibrated at the factory,
so its measurements should remain within
their specified tolerance for several years.
However, you can re-calibrate the unit
yourself to reassure yourself of the
accuracy of readings, especially after the
instrument has been operated for many
hours in a dusty environment.
To calibrate the EP8709, you must use
two jars of standard calibration salt: one
containing a 33% solution of MgCl and the
other a 75% solution of NaCl. Both are
available for purchase from General as
part numbers SKUs HR33 and HR75.
10
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