9-IN-1 THERMO-HYGROMETER/
MOISTURE METER
USER’S MANUAL
RHMG650
99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Please read this manual carefully and thoroughly before using this product.
TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 –4
Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Safety Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
What’s in the Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Product Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 –6
Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Install Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 – 12
Powering On and Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Selecting a Parameter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 –8
General Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 –9
Recalling Stored Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Setting Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 – 11
Measuring Moisture Levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 – 12
Checking Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Operating & Maintenance Tips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Warranty Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Return for Repair Policy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
INTRODUCTION
Thank you for purchasing General Tools & Instruments’ (General’s) RHMG650 9-in-1 ThermoHygrometer/Moisture Meter. Please read this user’s manual carefully and thoroughly before using
the instrument.
The RHMG650 is a handheld instrument that will prove useful to four groups of users: water
damage restoration contractors, HVAC/R system installers and technicians, facility maintenance
professionals and electronics manufacturers.
The first three groups will exploit the meter’s ability to measure, display and store/recall six
condensation-related parameters: temperature, relative humidity (RH), absolute humidity, dew
point, atmospheric pressure and vapor pressure. The meter’s large, primary readouts of each of
the last five parameters are accompanied by a smaller, secondary readout of the first parameter:
ambient temperature. The six parameters measured, monitored and displayed by the RHMG650
are most valuable in water damage remediation and the following two applications:
•
Environmental monitoring
facilities, wineries, freezers, shipping containers, HVAC/R installations, computer rooms, labs,
libraries, museums and saunas.
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of office buildings, greenhouses, food and equipment storage
•
Electronics manufacturing
. Alerts provided by the low RH alarm of the RHMG650 can
mitigate the risk of damaging high-voltage static discharges.
Water damage remediators will also make use of the RHMG650’s ability to calculate an
environment’s mixing ratio (often represented by the unit GPP, or grains per pound). 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 RHMG650’s atmospheric pressure sensor makes its calculations of GPP—as well as
dew point and vapor pressure—more accurate than those of competitive units which use
standard atmospheric pressure at sea level.
Another parameter of interest to water damage remediators is the moisture level of a substance
(typically, wood or building materials). The RHMG650 can measure this parameter using either a
pinless (non-marring) or pin-type (penetrating) probe; the meter includes both kinds of probe.
Operating in internal moisture mode, the meter uses a non-invasive (pinless) sensor on the back
of the unit to detect moisture up to 3/4 in. (20mm) below the surface of wallboard, masonry,
hardwood and softwood. It infers the level of moisture from the material’s capacitance, which the
meter measures by gauging its effect on an electric field that the meter generates each time it is
operated in internal moisture mode.
In internal moisture mode
, the meter exploits two physical phenomena to make its
measurements:
1. The linear relationship between a solid material’s moisture level and its dielectric
constant—and therefore its capacitance.
2. The so-called fringing-field effect—the slight spreading of the electric field produced by
current flowing between two electrodes when both electrodes are on the same side of a
material.
Behind the back cover of the RHMG650 are two metal plates. When the meter is powered on, the
plates are given small and opposite charges. The potential difference causes current to flow,
creating a three-dimensional electric field.
When the back of the meter is placed against one side of a material with moisture on or slightly
below its surface, the increased capacitance of the material distorts the electric field to an extent
that can be sensed (as a change in flux over the sensing area) and measured. Displayed readings
reflect the average moisture level of the material between its surface and the electric field’s
maximum penetration of 3/4 in. Moisture closer to the surface has a greater effect on readings
than moisture at the maximum penetration depth.
In external moisture mode
, the meter bases its measurements on the relationship between the
moisture content of a material and its electrical conductivity. The wetter a material, the higher its
conductivity. The two replaceable steel pins of the included external probe serve as the
electrodes of a conductance meter optimized for measuring moisture content. The meter displays
measurements in the unit %WME (Wood Moisture Equivalent).
For hard materials like wood or concrete, the meter’s readings largely reflect surface moisture
content because: 1) Moisture close to a surface has a greater effect on a reading than moisture
deep below it; and 2) The pins of the external probe are only 3/8 in. (10mm) long and cannot be
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driven deep into a hard material. For softer materials like soil, paper or powders, readings are
more likely to reflect the average moisture level of the material between its surface and the
penetration depth of the pins (normally far less than 3/8 in.).
The RHMG650 can store and recall 20 pairs of measurements in its nonvolatile memory. The
instrument also can be set up to sound an alarm if a measured RH or moisture level is above or
below a user-defined setpoint. Finally, the unit can track the maximum or minimum reading of
any parameter over the duration of a measurement session. The unit is powered by an included
“9V” battery.
KEY FEATURES
• Measures 1) ambient temperature, 2) relative humidity (RH), 3) absolute humidity (in
mg/L or g/m
level using pinless sensor, 6) absolute moisture level using included pin-type probe,
7) dew point, 8) atmospheric pressure and 9) vapor pressure
• Stores/recalls 20 pairs of readings
• Settable high and low alarms for RH, relative moisture level and absolute moisture
level
• Backlit LCD with 3-digit primary readout + 4-digit secondary readout
• Zero reset in pinless moisture level mode
• Min/Max, Data Hold, and 30-minute Auto Power Off functions
• 1 year limited warranty
3
), 4) GPP (mixing ratio—in grains per pound or g/kg), 5) relative moisture
SAFETY INSTRUCTIONS
Do not operate the RHMG650 in the presence of flammable or explosive gases.
The steel pins of the external moisture probe are very sharp. When using the probe, be careful
not to stab yourself or anyone else. Remember to replace the protective cap over the pins when
finished using the probe.
WHAT’S IN THE BOX
The RHMG650 comes in a soft pouch inside an illustrated box. Also inside the pouch are a
pin-type moisture probe, a sensor protection cap, a “9V” battery and this user’s manual.
PRODUCT OVERVIEW
Fig. 1 shows the names and locations of all of the controls, connectors and physical structures of
the RHMG650. Fig. 2 shows all possible indications on the unit’s LCD. Familiarize yourself with
the labels, positions and functions of all buttons and connectors before moving on to the Setup
Instructions and Operating Instructions.
4
Fig. 1. The controls and physical structures
of the RHMG650
A. Humidity/temperature sensor
B
B. Removable hanger tab
C. LCD
ON/OFF HOLD
D.
button powers it on.
button.
With meter off
With meter on
, pressing
, briefly pressing
button freezes primary and secondary readouts;
pressing and holding button powers meter off.
AX/MIN
E. M
level,
since entering that measurement mode.
button twice displays lowest reading
button. For all parameters except moisture
pressing button once displays highest reading
Pressing
since entering
E
H
that measurement mode. Pressing button a third
time resumes measurement and display of same
parameter.
ZERO
F.
Also used to enter alarm set mode
button.
With meter off
, used to disable Auto
.
K
Power Off (APO) function. In measurement mode, used to reset baseline of pinless moisture
MOIST INT
(
UNIT
G.
) measurements.
button.
In measurement mode, each press toggles between Imperial and metric
In memory mode
, used to clear stored readings.
measurement units for the following parameters: Ambient Temperature & Dew Point (°F or
3
°C); Absolute Humidity (mg/L or g/m
Vapor Pressure (mBAR or KPa).
to enter alarm set mode
H.
<DN
button.
In measurement mode, each press shifts mode selector one position to the
.
left. In memory mode, each press decrements record counter
mode, each press decreases alarm setpoint
I.
UP>
button.
In measurement mode, each press shifts mode selector one position to the
right. In memory mode, each press increments record counter
mode, each press increases alarm setpoint
J.
STORE/ENTER
button.
In measurement mode, stores both displayed readings
when pressed and held for >2 seconds.
setpoint
and advances to Lo alarm setting, or saves displayed Lo alarm setpoint and
resumes measurement mode.
); Mixing Ratio (GPP or g/kg); Barometric Pressure and
In memory mode, used to clear
stored readings.
by one digit.
In alarm set
by 0.1%.
by one digit.
by 0.1%.
In alarm set mode, saves displayed Hi alarm
In memory mode, exits memory
mode and resumes
In alarm set
in memory
measurement and display of last selected parameter.
K. Jack for included pin-type moisture probe
L. Pinless moisture sensor (on back)
M. Battery compartment (on back)
A
L
C
D
F
G
I
J
M
Also used
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