EP8711P - General Tools And Instruments

Please read this manual carefully and
thoroughly before using this product.
Introduction . . . . . . . . . . . . . . . . . . . . 2 – 4
Key Features . . . . . . . . . . . . . . . . . . . . . . . 4
What’s in the Package . . . . . . . . . . . . . . . 5
Product Overview . . . . . . . . . . . . . . . . 5 – 7
Setup Instructions . . . . . . . . . . . . . . . . . . 8
Install Batteries . . . . . . . . . . . . . . . . . . . 8
Operating Instructions . . . . . . . . . . . 8 – 10
Specifications . . . . . . . . . . . . . . . . . . . . . 11
Operating & Maintenance Tips . . . . . . . . 12
Warranty Information . . . . . . . . . . . 13 – 14
Return for Repair Policy . . . . . . . . . . . . . 14
Thank you for purchasing General Tools
& Instruments’ EP8711P 6-in-1 In-duct
Digital Psychrometer with Enthalpy. Please
read this user’s manual carefully and
thoroughly before using the instrument.
The EP8711P can measure any
environment’s ambient temperature,
relative humidity (RH), dew point and wet
bulb temperatures, absolute humidity
(mixing ratio) and enthalpy of vaporization.
These measurements are typically made by
three groups of users:
• 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. It is the lowest temperature that can be
reached under current ambient conditions
by the evaporation of water only. The wet
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. 3
An environment's absolute humidity level
(or mixing ratio) can be measured and
expressed in units of grains per pound
(GPP) or g/kg. GPP is a more useful
moisture metric than RH to water damage
remediators. Using RH alone, a remediator
might unknowingly introduce moist air—
with a low RH but a high GPP—during a
job’s drying phase.
The sixth environmental parameter that the
EP8711P can measure is enthalpy. Enthalpy
is a measure of the amount of energy
needed to change the state of a substance
from a solid to a liquid or from a liquid to a
gas. The most common application for the
EP8711P's enthalpy-calculating algorithm is
measuring the enthalpy of vaporization of
air in an HVAC/R system duct.
The EP8711P is powered by (3) “AAA”
batteries (included).
• Integral 6 in. long sensor-tipped probe for
measuring conditions inside ductwork.
Probe swivels, increasing placement
• Choice of Imperial or metric units for all
measured parameters except RH
• 4-digit LCD
• 2-minute Auto Power Off (APO) function
• Low battery indicator
The EP8711P comes fully assembled in a
blister pack along with a rubber bushing for
inserting the probe into ductwork, (3) “AAA”
batteries and this user’s manual.
Figure 1 shows all of the controls, indicators
and physical structures on the front and
back of the EP8711P. 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
Instructions and Operating Instructions.
Fig. 1. The EP8711P’s controls, indicators
and physical structures
A. Humidity and temperature sensors under
protective cap
C. MODE button
D. UNIT button
E. Pocket clip
F. Battery compartment
G. Rubber bushing for inserting probe in
Fig. 2. All possible display indications and
their meanings
RH = Relative humidity mode indicator
TEMP = Temperature mode indicator
DEW = Dew point mode indicator
WET = Wet bulb mode indicator
MIX = Mixing ratio mode indicator
ENTH = Enthalpy mode indicator
GPP = Mixing ratio Imperial unit
g/kg = Mixing ratio metric unit
kJ/kg = Enthalpy metric unit
BTU/lb = Enthalpy Imperial unit
°F = Fahrenheit indicator
°C = Celsius indicator
= Low battery indicator
1. The meter’s battery compartment (Fig. 1,
Callout F) is accessible from the bottom
of the unit. Slide the battery compartment
cover down and away from the EP8711P
and set it aside.
2. Insert the three supplied “AAA” batteries
in the compartment, orienting them as
shown on the diagram stenciled on the
battery compartment cover
3. Replace the battery compartment cover
and slide it up until it latches shut.
Before making any measurements, rotate
the sensor protection cap (Fig. 1, Callout A)
with your thumb and index finger so both of
its vents are open to the ambient
environment. Press the MODE button to
power on the meter. The LCD will
immediately begin reading out the RH value
of the environment. The reading will be
accompanied by the term RH in the upper
left corner of the LCD.
To display the ambient temperature, press
the MODE button once. TEMP will replace
RH on the top line of the LCD.
To display the dew point temperature,
press the MODE button again. DEW will
replace TEMP on the top line of the LCD.
To display the wet bulb temperature, press
the MODE button again. DEW will disappear
from the top line of the LCD and be
replaced by WET on the bottom line.
To display the mixing ratio (absolute
humidity) of the environment, press the
MODE button again. MIX will replace WET
on the bottom line of the LCD.
To display the enthalpy of the environment,
press the MODE button again. ENTH will
replace MIX on the bottom line of the LCD.
How pressing the MODE button changes
the measured parameter
For all parameters except RH, the EP8711P
will automatically display readings in
Imperial units. To switch to metric units
for ambient, dew point or wet bulb
temperature, mixing ratio or enthalpy, press
the UNIT button. To toggle back to Imperial
units, press the UNIT button again.
The placement of the EP8711P’s humidity
and temperature sensors at the end of a
probe makes it possible to take readings
inside ductwork. And the fact that the probe
swivels increases positioning options if the
probe is inserted through a vent or grille.
If you wish to measure duct conditions
where there is no grille or duct nearby,
consider drilling a temporary hole in the
ductwork and inserting the probe through it.
The black rubber bushing is provided for
this purpose. It is sized for a 1 in. diameter
hole. Inserting the probe through it will
extend the sensor 4 in. into the duct.
To extend the life of the batteries powering
the EP8711P, the unit’s Auto Power Off
(APO) function will automatically shut down
the instrument if no front-panel buttons are
pressed within any 2-minute period.
To power off the EP8711P, press and hold
the MODE button for at least 3 seconds.
Ambient Temperature Measurement Range:
-4° to 158°F (-20° to 70°C)
Ambient Temperature Measurement
Accuracy: ±0.9°F (0.5°C) from 14° to
104°F (-10° to 40°C); ±1.8°F (1°C)
elsewhere in range
Temperature Measurement Resolution: 0.1°
RH Measurement Range: 0 to 100%
RH Measurement Accuracy:
±3% from 20 to 80%RH;
±3.5% elsewhere
RH Measurement Resolution: 0.1%
Dew Point Temperature Measurement
Range: -76° to 158°F (-60° to 70°C)
Wet Bulb Temperature Measurement Range:
-49° to 158°F (-45° to 70°C)
Mixing Ratio Range: 0 to 999 GPP
(0 to 280g/kg)
Enthalpy Range: -8 to 318 Btu/lb.
Probe Length: 6 in. (150mm)
Display Size: 1.5 in. (38mm) diagonal
Current Consumption: <10mA
Battery Life: 1000 hours (typical)
Dimensions: 8.23 x 1.85 x 1.85 in.
(209 x 47 x 47mm)
Weight (without battery): 2.2 oz. (63g)
Power Source: (3) “AAA” batteries (included)
When the
icon appears on the top
line of the display, it’s time to replace the
batteries that power the instrument
(although measurements will remain valid
for several hours after the icon first
appears). To replace the batteries, follow the
instructions on page 8.
To prevent dust and moisture from
degrading the performance of the humidity
and temperature sensors, after each
measurement session rotate the sensor
protection cap to close its three vents.
Do not operate the EP8711P in the
presence of a flammable or explosive gas or
near an arc welder or induction heater.
After subjecting the unit to a large change
in ambient temperature, wait at least
30 minutes before making measurements
to guarantee the accuracy of readings.
Remove the batteries when storing the unit
or when you do not expect to use it for an
extended period of time (months rather
than weeks).
Do not drop or disassemble the EP8711P or
immerse it in water.
General Tools & Instruments’ (General’s)
EP8711P 6-in-1 In-duct Digital
Psychrometer with Enthalpy is warranted
to the original purchaser to be free from
defects in material and workmanship for
a period of one year. Subject to certain
restrictions, General will repair or replace
this instrument if, after examination, the
company determines it to be defective in
material or workmanship. The warranty
period begins on the date of purchase. You
are encouraged to register your product
online. General will extend your warranty
an additional 60 days if you register at
This warranty does not apply to damages
that General determines to be from an
attempted repair by non-authorized
personnel or misuse, alterations, normal
wear and tear, or accidental damage.
The defective unit must be returned to
General Tools & Instruments or to a
General-authorized service center, freight
prepaid and insured.
Acceptance of the exclusive repair and
replacement remedies described herein is a
condition of the contract for purchase of this
product. In no event shall General be liable
for any incidental, special, consequential or
punitive damages, or for any cost, attorneys’
fees, expenses, or losses alleged to be a
consequence of damage due to failure of,
or defect in any product including, but not
limited to, any claims for loss of profits.
Register now at
to receive a 60-day extension to
your warranty.
Every effort has been made to provide you
with a reliable product of superior quality.
However, in the event your instrument
requires repair, please contact our
Customer Service to obtain an RGA (Return
Goods Authorization) number before
forwarding the unit via prepaid freight to the
attention of our Service Center at this
General Tools & Instruments
75 Seaview Drive • Secaucus, NJ 07094
Remember to include a copy of your proof
of purchase, your return address, and your
phone number and/or e-mail address.
75 Seaview Drive Secaucus, NJ 07094-1806
PHONE (212) 431-6100 FAX (212) 431-6499
TOLL FREE (800) 697-8665
e-mail: sales@generaltools.com
EP8711P User’s Manual
Specifications subject to change without notice
MAN# EP8711P
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