General RHMG650 User manual

9-IN-1 THERMO-HYGROMETER/
MOISTURE METER
USER’S MANUAL
RHMG650
Please read this manual carefully and thoroughly before using this product.

TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 –4
Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Safety Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
hat’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
arranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Return for Repair Policy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
INTRODUCTION
Thank you for purchasing General Tools & Instruments’ (General’s) R MG650 9-in-1 Thermo-
ygrometer/Moisture Meter. Please read this user’s manual carefully and thoroughly before using
the instrument.
The R MG650 is a handheld instrument that will prove useful to four groups of users: water
damage restoration contractors, VAC/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 (R ), 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 R MG650
are most valuable in water damage remediation and the following two applications:
•
Environmental monitoring of office buildings, greenhouses, food and equipment storage
facilities, wineries, freezers, shipping containers, VAC/R installations, computer rooms, labs,
libraries, museums and saunas.
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• Electronics manufacturing . Alerts provided by the low R alarm of the R MG650 can
mitigate the risk of damaging high-voltage static discharges.
Water damage remediators will also make use of the R MG650’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 R to water damage remediators. Using R alone, a remediator
might unknowingly introduce moist air—with a low R but a high GPP—during a job’s drying
phase. The R MG650’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 R MG650 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 R MG650 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
3

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 R MG650 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 R 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 (R ), 3) absolute humidity (in
mg/L or g/m3), 4) GPP (mixing ratio—in grains per pound or g/kg), 5) relative moisture
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 R , 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 old, and 30-minute Auto Power Off functions
• 1 year limited warranty
SAFETY INSTRUCTIONS
Do not operate the R MG650 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 R MG650 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 R MG650. 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.
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Fig. 1. The controls and physical structures
of the RHMG650
A. umidity/temperature sensor
B. Removable hanger tab
C. LCD
D.
ON/OFF HOLD button. With meter off , pressing
button powers it on.
With meter on , briefly pressing
button freezes primary and secondary readouts;
pressing and holding button powers meter off.
E. M
AX/MIN button. For all parameters except moisture
level,
pressing button once displays highest reading
since entering that measurement mode. Pressing
button twice displays lowest reading
since entering
that measurement mode. Pressing button a third
time resumes measurement and display of same
parameter.
Also used to enter alarm set mode .
F.
ZERO button. With meter off , used to disable Auto
Power Off (APO) function. In measurement mode, used to reset baseline of pinless moisture
(
MOIST INT ) measurements. In memory mode , used to clear stored readings.
G.
NIT button. In measurement mode, each press toggles between Imperial and metric
measurement units for the following parameters: Ambient Temperature & Dew Point (°F or
°C); Absolute umidity (mg/L or g/m3); Mixing Ratio (GPP or g/kg); Barometric Pressure and
Vapor Pressure (mBAR or KPa).
In memory mode, used to clear stored readings. Also used
to enter alarm set mode
.
.
<DN button. In measurement mode, each press shifts mode selector one position to the
left. In memory mode, each press decrements record counter
by one digit. In alarm set
mode, each press decreases alarm setpoint
by 0.1%.
I.
P> button. In measurement mode, each press shifts mode selector one position to the
right. In memory mode, each press increments record counter
by one digit. In alarm set
mode, each press increases alarm setpoint
by 0.1%.
J.
STORE/ENTER button. In measurement mode, stores both displayed readings in memory
when pressed and held for >2 seconds.
In alarm set mode, saves displayed Hi alarm
setpoint
and advances to Lo alarm setting, or saves displayed Lo alarm setpoint and
resumes measurement mode.
In memory mode, exits memory mode and resumes
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)
5
A
B
C
D
F
G
I
J
M
E
H
K
L

Fig. 2. All possible display indications
▼: Mode selector
: Relative humidity mode indicator
: Absolute humidity mode indicator
[Upper] : Dew point mode indicator
: Vapor pressure mode indicator
: GPP mode indicator
: Ambient pressure mode indicator
: Pin-type moisture measurement mode
indicator
: Pinless moisture measurement mode
indicator
: Alarm limit indicators
: Zero reset indicator
: Pin/pinless moisture level indicator
: Maximum & minimum value
indicators
: Data hold indicator
: Primary readout
: Secondary readout
: Recall mode indicator
: Record number indicator
: Low battery icon
[Lower] : Dew point temperature indicator
: Auto power off enabled indicator
: Mixing ratio units
: Absolute humidity units
: Relative humidity unit
: Temperature units
: Pressure units
,
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SETUP INSTRUCTIONS
INSTALL BATTERY
To open the battery compartment:
1. Turn the meter over and loosen the single screw securing the battery compartment cover.
Remove the screw and set it aside.
2. Lift the tab at the bottom of the cover in order to remove it and set it aside.
3. 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.
4. Replace the battery compartment cover and reinstall the screw to secure it.
OPERATING INSTRUCTIONS
POWERING ON & OFF
To power on the meter , press the ON/OFF HOLD button. By default, the instrument will
immediately begin making and displaying R (relative humidity) measurements.
Before using the meter to make measurements, remove the dust cap protecting the
humidity/temperature sensor.
To power off the meter , press and hold the ON/OFF HOLD button for at least 2 seconds. The
shutdown will be announced by two short beeps.
After powering off the meter, replace the sensor protection cap if you do not expect to use the
instrument within the next few hours.
By default, the meter will automatically power itself off if no front-panel button is pressed within
any 30-minute period. The upcoming shutdown will be announced by three beeps of the beeper.
When this Auto Power Off function is active, the term
APO will appear at the bottom left of the
LCD (see Fig. 2).
To disable the APO functio n, you must power on the meter in a special way, by pressing and
holding the
ZERO button while pressing the ON/OFF HOLD button. When the APO function has
been disabled, the term
APO will not appear on the LCD.
SELECTING A PARAMETER
The R MG650 can measure and display the value of eight different
moisture-related parameters. When the meter is in measurement
mode, you select a parameter by pressing either the
P> and <DN
buttons to move the ▼pointer on the top line of the LCD directly
above it. For example, the following is the display for R
measurement mode—the operating mode that the meter enters by
default when it is powered on.
7
°F

As the figure on the left shows, moving the ▼ pointer four
positions to the right (by pressing the
P> button four times)
switches the meter to operate in Ambient pressure mode.
In Dew point measurement mode, will appear at the left of
the secondary readout to remind you that the value shown reflects
the dew point temperature, rather than the ambient temperature.
GENERAL CONTROLS
Changing measurement units . By default, the R MG650 uses Imperial units for all parametric
readouts.
To switch to metric units , press the NIT button. Ambient temperatures and dew points
will then be displayed as °C rather than °F; absolute humidity values will be stated in g/m3rather
than in mg/L; mixing ratios will be displayed in units of g/kg rather than GPP; and barometric
pressures and vapor pressures will be stated in KPa rather than mBAR.
Backlight . The R MG650 has a green backlight that automatically illuminates whenever any
button is pressed. It will remain on for 30 seconds and then extinguish to extend battery life.
Holding readings . Briefly pressing the ON/OFF HOLD button freezes
both the primary and secondary readouts. will appear on
the display to remind you that the readouts are frozen.
To release the hold, briefly press the
ON/OFF HOLD button again.
Note: When the R MG650 is in old mode, it takes two separate
presses of the
ON/OFF HOLD button to power off the meter. The first
(brief) press (which is accompanied by a short beep) releases the
hold. The second press (and hold) initiates shutdown (which is announced by two short beeps).
Storing readings . Pressing and holding the STORE/ENTER button for at least 2 seconds saves the
values shown on the primary and secondary readouts as a pair in the meter’s nonvolatile
memory. Each “save” automatically increases by one the Record number indicator—the number
above
MEM at the lower left of the LCD. The readings remain in memory, available for recall, after
the meter powers off.
The next section of this manual contains instructions for recalling saved readings.
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MIN/MAX tracking . For all parameters except moisture level:
• Pressing the MAX/MIN button once displays the highest reading since entering that
measurement mode. will appear at the left of the primary readout.
•
Pressing the button twice displays the lowest reading since entering that measurement
mode. will appear at the left of the primary readout.
•
Pressing the button a third time resumes real-time measurement and display of the same
parameter.
RECALLING STORED READINGS
To enter Recall mode , press the <DN and P> buttons at the same time. will appear
above the Record number indicator at the lower left of the LCD. The Record number indicator will
correspond to the last pair of readings stored.
You can now use the
<DN and P> buttons to navigate to and display a specific pair of readings.
For example, the screen shot below shows that a pair of readings of 63.8% for R and 28.8°C for
temperature were stored in Record location 08.
Alternatively, you can repeatedly press the
P> button to recall all
readings in the order in which they were stored, or the
<DN button to
recall them in reverse order. Pressing the
P> button when the last
stored pair of readings is displayed returns the Record number
indicator to 01, corresponding to the first pair of readings stored.
Pressing the
<DN button when the first stored pair of readings is
displayed returns the indicator to the record number of the last pair
of readings stored.
To exit Recall mode and resume making real-time measurements, press the STORE/ENTER
button.
To erase all stored readings , press and hold the ZERO and NIT
buttons at the same time for at least 2 seconds. The meter will
respond by sounding three short beeps and resetting the Record
number to 01. You can clear all stored readings while operating in
Recall mode or Measurement mode. Clearing the memory in Recall
mode produces the display at left.
SETTING ALARMS
The R MG650 allows you to set alarms that will repeatedly sound the beeper if the measured
R level or the moisture level of a material (measured by either the pinless or pin-type sensor)
is above or below a certain value. The upper and lower limits are called alarm setpoints. For
example, the screen shot at the top of the next page shows that the upper limit for R —the
HIGH setpoint of the R alarm—has been set to 63.8%.
9

T o enter Alarm set mode , press the MAX/MIN and NIT buttons at
the same time while in
RH, MOIST INT or MOIST EXT mode. Doing so
will display the current value of the selected parameter’s high
setpoint and cause the word
HIGH to appear near the upper left of
the display, as shown on the left.
All three parameters require you to use the same three-step
sequence of button presses for changing their setpoint(s). After
entering Alarm set mode (with
HIGH appearing on screen), you can either raise or lower the HIGH
setpoint by using the P> or <DN button, or leave it unchanged (if you wish to change only the
LOW setpoint). Each press of the P> button increases the setpoint by 0.1%. Each press of the
<DN button decreases the setpoint by 0.1%. To change the value of the setpoint by a large
amount, you can press and hold the
P> or <DN button for at least 3 seconds.
Whether or not you change the
HIGH setpoint, you must press the STORE/ENTER button to
proceed to the next step in the sequence: changing the
LOW setpoint or leaving it unchanged.
Pressing the
STORE/ENTER button with HIGH on-screen saves the value shown on the primary
readout as the selected parameter’s new
HIGH setpoint. It also changes HIGH to LOW and
switches the primary readout to show the current value of the parameter’s
LOW setpoint.
Once
LOW appears on-screen, you can use the P> or <DN button to change the value of the
parameter’s
LOW setpoint, as explained earlier in the paragraph on HIGH setpoints. Alternatively,
you can leave the
LOW setpoint unchanged. Whether or not you make a change, your next step
must be to press the
STORE/ENTER button. Doing so saves the value shown on the primary
readout as the selected parameter’s new
LOW setpoint. It also causes LOW to disappear and
returns the R MG650 to operation in real-time R measurement mode.
To disarm any of the six alarms ( HIGH and LOW for RH, MOIST INT and MOIST EXT ), you must
reset its setpoint to 100.0% or 0.0% by pressing the
P> or <DN button. When disarming a HIGH
alarm, it is faster to use the P> button to increase its setpoint to 100% than to use the <DN
button to decrease its setpoint to 0.0%. In practice, what you would do is: 1) press and hold the
P> button until the display shows a value greater than 99%, 2) release the button, and 3) use
brief presses to reach 99.9%. When the primary readout shows 99.9%, the next press of the
P>
button will change the readout to OFF . Pressing the STORE/ENTER button at this point will disarm
the
HIGH alarm for that parameter.
Similarly, you would disarm a
LOW alarm by 1) pressing and holding the <DN button until the
display shows a value less than 1%, 2) releasing the button, and 3) using brief presses to reach
0.1%. When the primary readout shows 0.1%, the next press of the
<DN button will change the readout to OFF . Pressing the
STORE/ENTER button at this point will disarm the LOW alarm for that
parameter. The screen at left shows the next-to-last step (prior to
pressing the
STORE/ENTER button) of disarming the LOW alarm for
MOIST INT .
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