Tramex MRH3 User manual

user guide

MRH III

non-destructive

moisture & humidity meter

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MRH III USER GUIDE

TABLE OF CONTENTS

Introduction..........................................................................................3

How it works....................................................................................4-5

Instrument Features ..................................................................6-7

Operating Instructions ..................................................................8

Non-Destructive Measurement Mode ..........................9-10

Wood Pin Meter Mode ........................................................11-12

Non-Destructive Measurement Mode

- Comparative Scales ................................................................14- 17

Roof Scale ........................................................................14-15

Masonry Scale ...............................................................15-16

Drywall Scale .........................................................................16

Laminate Scale .....................................................................17

Non-Destructive Measurement Mode

- Wood Scale ............................................................................17-24

Relative Humidity & Moisture Content....................19

Wood Flooring ..............................................................20-21

Specific Gravity Adjustment Table ............................21

Table of Wood Specific Gravities (SG) .............23-24

Wood Pin Meter Mode .......................................................25-29

Species Correction Chart .................................................30-41

Humidity Measurement Mode .......................................42-43

Moisture Testing Guidelines ...........................................44 -45

Hole Liner Instructions ASTM F2170 / BS 8201,

8203, 5325 ..........................................................................46 -4 9

Calibration Check Salts .....................................................50-51

Limitations.......................................................................................52

Calibration ......................................................................................52

Warranty............................................................................................53

Product Development................................................................54

Safety ......................................................................................................54

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MRH III USER GUIDE

INTRODUCTION

Thank you for selecting the new MRH III instrument,
from Tramex. It has 3 measurement modes.

1. The MRH III utilises electronic technology to

provide you with an accurate and easy to use
non-invasive instrument for the non-destructive
measurement and tracing of moisture in a wide
range of building materials.

2. By inserting one of the optional plug-in

electrodes for wood and selecting Pin Probe the
instrument can then be used in Pin Probe (wood
pin-meter resistance measurement) Mode. This
enables the MRH III to measure the percentage
moisture content (MC%) of wood and give an
indication of the moisture content of wood­based products.

3. By inserting the optional plug-in Hygro-i2

probe, the instrument automatically changes to
hygrometer mode. This enables the MRH III to
measure relative humidity (RH), temperature,
dew-point temperature and mixing ratio of the
environment or equilibrium relative humidity in
a structural material. A structural material such
as a concrete slab can be tested using the in-situ
method as per ASTM F2170 and the in-situ
and hood methods as per British Standards BS
8201, 8203, 5325.

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HOW IT WORKS

In non-destructive moisture measurement mode i.e.
without the plug-in probes, the instrument operates
on the principle that the electrical impedance of
a material varies with its moisture content. The
electrical impedance is measured by creating a low
frequency alternating electric field between the
electrodes as illustrated in Figure 1.

This field penetrates the material under test. The
very small alternating current flowing through the
field is inversely proportional to the impedance of
the material. The instrument detects this current,
determines its amplitude and thus derives the
moisture value.

Figure 1

MRH III

Material

Alternating Electric Field

Sample

Transmiting
Electrode

Receive

Electrode

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In Pin Probe Mode (i.e. with pin probe mode selected and
an electrode plugged in), the MRH III is a resistance-type
pin meter for determining the percentage moisture
content of wood.

In Hygrometer mode (i.e. with the Hygro-i2 Probe
plugged in), the MRH III determines the capacitance
of the RH probe sensor, which varies with the relative
humidity of the test area environment. The MRH
III displays this capacitance as percentage relative
humidity (%RH). It also measures temperature and
displays dew-point temperature and mixing ratio.

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INSTRUMENT FEATURES

Your MRH III employs advanced digital technology to
enable the incorporation of many features, which are
listed below.

● 3 modes of measurement: Non-destructive
moisture measurement, hygrometer and wood
pin probe.

● 6 simple membrane keypad controls:

ON/OFF
SCALE
UP
DOWN
HOLD / AUDIO
BACKLIGHT

● 5 Scales: Wood, Roof, Masonry, Drywall and
Laminate. These are selected using the key
and or keys.

● Moisture readings and scale are displayed on a
clear easy to read liquid crystal display (LCD).

● Relative Humidity (RH) readings, probe
temperature, dew-point temperature and mixing
ratio are automatically displayed when the RH
Probe is plugged into the MRH III (Hygrometer
Mode).

● The Roof, Masonry, Drywall and Laminate
Scales use a reference/comparative scale that
is displayed both numerically (0-99) and in a
bar form on the bottom line of the display. The
display also shows low (LO), medium (MD) and
high (HI) readings for these scales.

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These do not necessarily indicate low, medium or high
levels of moisture but indicate the area of the
0-100 comparative scale where the reading lies

Example:

● To conserve battery life, the instrument
automatically powers OFF after 10 minutes of
inactivity or when the key is pressed. If a key is
pressed the power off will will be extended for an
additional ten minutes.

● Backlit display allows the display to be easily read
in poor light conditions. This is enabled by pressing
the key. The backlight stays on for a period of
time set.

● Backlight display time. To adjust the backlight
display time, press the and keys together.
Then scroll with the key from 10 – 60 seconds.
When time is chosen select key to confirm and
return to scale mode.

● Language display adjustment. To adjust the
language display, press the and keys
together. Then scroll with the key through the
language library. When language is chosen select
key to confirm and return to scale mode.

● When the battery requires replacement a LOW
BATTERY message is shown on the LCD.

● HOLD freezes reading to facilitate ease of
recording readings. When the MRH III is in HOLD
mode, ‘H’ will flash on the display.

● If HOLD was selected prior to the MRH III
automatically powering off, the frozen display
reading is digitally memorized and restored next
time ON is selected.

.

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OPERATING INSTRUCTIONS

1

3

5

6

1 = Phono socket for Wood Probes.
2 = Hygro-i2 Probe Socket (automatic hygrometer mode

when plugged in).

3 = Backlit display.
4 = Hold / Audio Mode.
5 = Scale Key.
6 = UP / DOWN Keys
7 = ON / OFF Key 10 minute switch off
8 = Light Key.

2

4

8

7

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NON-DESTRUCTIVE MEASUREMENT MODE

1. Press the key to power up. With no RH probe
connected the last used scale will be displayed on
the LCD. Press key again to power off.

2. To change scale, press key to select the wood
scale or the comparative material scales. Select
the required material scale using the or key.

3. Hold your MRH III directly on the wood, roof,
masonry, drywall, laminate or other material
being tested, ensuring both conductive-rubber
electrodes are fully in contact with the surface.

4. For the Roof, Masonry, Drywall and Laminate
scales the readings are comparative from 0 to

99. A visual indication is also given by the bar
display on the bottom line of the LCD. The display
also shows low (LO), medium (MD) and high (HI)
readings for these scales. LO is displayed for
readings from 0 to 30, MD for readings from 31 to
70 and HI for readings from 71 to 99.

These do not necessarily indicate low, medium or
high levels of moisture but indicate the area of
the 0-100 comparative scale where the reading
lies.

5. The readings on these scales are not to be
interpreted as a measurement of percentage
moisture content (MC%) or relative humidity (RH).
It is not a relative humidity reading and it does not
have any linear correlation with Relative Humidity
measurements. This scale should be regarded as a
comparative or qualitative scale only.

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6. When the Wood Scale is selected the moisture
content (MC%) in percent of wood is shown on the
right-hand side of the bottom line of the display.
The left-hand side of this line shows the specific
gravity (SG) being used. The SG is changed by using
the or key to adjust to the required SG
value. The range of SG covered is 0.30 to 0.80. The
SG increases and decreases in increments of 0.01.

7. A chart showing the approximate specific gravity
of a wide range of different species is shown on
pages 23 and 24. For SG greater than 0.80 please
refer to species adjustment table (Table on Page

21).

8. To turn audio tone on or off, press key twice in
quick succession.

9. The MRH III will automatically power-off after ten
minutes if no key is pressed. If a key is pressed the
power-off will be extended for an additional ten
minutes.

10. To freeze readings press the key once. While
on HOLD, H will flash slowly on the upper line of
the display. If the unit powers OFF while on HOLD,
the frozen meter reading is digitally memorized
and restored next time ON is selected. To remove
freeze, press key again.

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WOOD PIN METER (PIN PROBE) MODE

This mode is activated by plugging one of the optional
Wood Electrodes into the socket at the top of the
instrument and selecting Pin Probe using the key.
In pin probe mode the MRH III works on the principle
of electrical resistance. When the electrode pins are
pressed or driven into the wood, the electrical resistance
between the electrodes is measured and indicated on
the digital display. If the wood is dry, the resistance is
very high. The higher the moisture content, the lower
the resistance. This resistance is accurately measured
by the instrument, which translates it into percentage
moisture content for wood. The MRH III gives moisture
readings from 7% to 40%. It should be noted that
readings above 27% (nominal value of the fibre­saturation point) are indicative only.

Wood Pin Meter Mode Vs. Non-Destructive
Measurement Mode

The two main types of moisture meter for measuring
moisture content in wood are the pin type meter and the
non-destructive or impedance type meter. Both types
are calibrated using gravimetric or oven-drying test
methods.

The Tramex MRH III combines both of the above
methods in one instrument so it is important to
understand how each test method works as the results
from the two tests may sometimes be different and
appear to be contradictory.

The pin type meter measures the resistance between
two pins, which are inserted into the timber. The
standard calibration for this type of meter is based on
Douglas Fir with a specific gravity (SG) of 0.5.

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The impedance or non-destructive type meter has two
electrodes, which transmit a low frequency signal into
the timber up to a maximum depth of 1¼" (30mm). This
meter takes an average reading over a much larger area
but the SG of the material being tested has a significant
effect on the reading.

On the MRH III non-destructive test it is possible to
adjust the specific gravity for better species-dependant
readings if the material is of sufficient thickness. If the
SG of the material is not known it is possible to use the
readings from the pin meter to give an approximation
of the SG for the non-destructive meter. This is done
by adjusting the SG on the non invasive test until both
tests give approximately the same reading. This is not
as accurate as knowing the exact SG of the material but
can be a good indication.

It is very important to note that the readings of the
non-destructive meter will penetrate up to 1¼" (30mm)
into the material being tested. If the material is less than
1¼" (30mm) thick it is possible to get false readings
from another material in contact with it. A typical
example of this would be a laminate floor over concrete.

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Typical MRH III Displays

Moisture Measurement Mode

Battery warning

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NON-DESTRUCTIVE MEASUREMENT MODE –
Comparative Scales

The MRH III has 4 comparative material scales: Roof,
Masonry, Drywall and Laminate. The comparative
material scales are selected using the key and
switching between the various scales using or key.

Roof Scale - Roof Testing

a. The presence of moisture in roofing systems

covered with multi-ply roofing felt, PVC, modified
bitumen and all non-conductive membranes (See
Limitations Section), can cause blistering and
splitting of the roof covering. In addition moisture
can cause considerable damage to the contents
and fabric of the building as well as heat loss
through wet insulation. Your MRH III can be used to
confirm a new roof has been installed dry and help
trace leaks.

b. If the waterproofing membrane develops a leak,

the water can travel within the structure and
enter the building some distance away. Testing the
membrane surface and comparing the dry areas
with areas where moisture is present below the
surface can assist in tracing such a leak back to its
source.

c. As there are many different types and thicknesses

sizes of roofing membranes, it is not possible
to give a calibrated percentage measurement.
Instead, a comparative scale is displayed both
numerically, (0 to 99) and in a bar form on the
bottom line of the display. The display also shows
low (LO), medium (MD) and high (HI) readings for
the scale.

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These do not necessarily indicate low, medium or high
levels of moisture but indicate the area of the 0-99
comparative scale where the reading lies.

d. If gravel surfacing is present, this should be

removed to ensure your MRH III comes into direct
contact with the surface of the membrane.

e. It is recommended that a core be cut to determine

the depth and density of the moisture before
carrying out roof repairs. Alternatively, the area
can be checked with a resistance-type moisture
meter with insulated pins up to a length of 7"
(180mm).

Masonry Scale - Testing Plaster, Brick and Block

Your MRH III gives comparative (relative) readings (0
to 99) on plaster, brick and block. These readings are
displayed both numerically and in bar form on the LCD.
The display also shows low (LO), medium (MD) and high
(HI) readings for the scale.

These do not necessarily indicate low, medium or high
levels of moisture but indicate the area of the 0-99
comparative scale where the reading lies.

For plaster, brick and block use the Masonry scale. For
drywall the more sensitive dedicated Drywall scale
is used. Always press the electrodes firmly against
the surface. The moisture profile of a masonry wall
can be determined by moving your MRH III across the
surface where it will read through most paints and wall
coverings. It will help identify the different levels of
moisture even if not apparent on the surface. Moisture
can often be trapped behind wall coverings.

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Rising damp and moisture migration from leaks and
defective, or non-existent, vapor barriers can be
identified and profiled and often its source identified by
moving the instrument across the wall surface.

Water damage following flooding or fire fighting can
be checked and the drying out and de-humidification
process can be monitored.

Drywall Scale

Because of its deep signal penetration, your MRH III can
identify excess moisture behind drywall, ceramic tile and
other wall coverings when used on the Drywall Scale.

Testing on ceramic tiles, other wall and floor coverings.

Excess moisture trapped behind covering materials such
as ceramic tiles, carpet, wall coverings etc can cause
major problems. For instance, excess moisture behind
ceramic tiles on drywall or other substrates can cause
decay, delamination and mold growth. The longer these
problems go undetected, the worse the problem can get,
eventually leading to system failure.

Your MRH III can be used to detect and identify areas of
elevated moisture within or behind most types of wall
and floor coverings. For example the MRH III can detect
elevated moisture behind most types of ceramic tiles.

Should the Drywall Scale prove to be too sensitive
for testing ceramic tiles or other coverings, reduce
sensitivity by choosing the Laminate Scale and take
readings on a comparative basis.

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Laminate Scale

For applications where the Roof or Drywall scales are
too sensitive and the Masonry scale is not sensitive
enough, the Laminate scale can be used. This scale
can be used for testing on ceramic tiles and other wall
and floor coverings. It can also be used in many other
applications where the other scales do not have the
required sensitivity.

NON-DESTRUCTIVE MEASUREMENT MODE – Wood
Scale

Testing wood and wood products

a. When testing wood, power-on, select Wood Scale

using the key.

b. When the Wood Scale is selected the moisture

content (MC) in percent is shown on the right-hand
side of the bottom line of the display. The left-hand
side of this line shows the specific gravity (SG)
being used. See note on specific gravity on page

21. The SG is changed by using the or key
to adjust to the required SG value. The range of
SG covered is 0.30 to 0.80. The SG increases and
decreases in increments of 0.01.

c. A chart showing the approximate specific gravity

of a range of different species is shown on pages
23 and 24. For SG greater than 0.80 please refer
to specific gravity adjustment chart (Table on page

21). For species not listed a more comprehensive
list is available on the USDA website www.fpl.
fs.fed.us (in the US) or from timber importers and
forestry departments in other countries.

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d. If possible, always take readings with the length

of the instrument parallel to the direction of the
wood grain.

e. Calibration tests were carried out by Forbairt,

the Irish Institute for Industrial Research and
Standards, and are based on Douglas Fir, which had
a published specific gravity (SG) of 0.50.

f. Acceptable levels of moisture content depend on

climatic conditions and we advise you check the
levels acceptable in your area. The Table on page
19 shows the approximate relationship between
the ambient relative humidity and equilibrium
moisture content in woods.

g. The following moisture content levels are given as

a guide:

● Furniture: 5% to 6% when used in locations of low
relative humidity and up to 10% to 11% may be
acceptable where the relative humidity is higher.

● Interior wood: 6% in low humidity areas. Up to 12% in
higher humidity locations.

● Exterior wood: 10% to 15% depending on local humidity
levels.

● Generally, wood with a moisture content in excess of 23%
to 25% is susceptible to rot.

● Wood moisture content in excess of 18% to 20% may
provide an environment for termite and woodboring
insects to thrive and multiply. Wood at these high levels
can also support mold and biological growth.

● Wood at 28% moisture content is considered to have
reached fiber saturation point.

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h. Avoid taking readings on wood from the top of a

stack stored outside as these may be affected by
surface moisture from recent rain.

i. When taking readings in chemically treated wood,

it is advisable to allow for possible effects that the
treatment may have on readings.

Relative Humidity and Moisture Content

The following table shows the approximate relationship
between relative humidity (RH) and equilibrium
moisture content (EMC) of some woods. These figures
are approximate values and may vary for different
species.

Approx. relationship between RH and EMC.

Relative Humidity Wood MC %

10 % 3 to 5
20 % 5 to 6
30 % 6 to 8
40 % 8 to 10
50 % 10 to 11
60 % 11 to 13
70 % 13 to 15
80 % 15 to 18
90 % 18 to 23

100 % 23 +

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Depth of field penetration

Depending on the density of the material being tested,
the instrument field can penetrate approximately 30mm
(1¼") below the surface. When testing thin materials
such as wood veneers it is recommended that they are
stacked to at least that thickness.

Wood Flooring

a. Excess moisture in wood flooring or concrete

sub-floors can cause major problems. For instance,
if installed with excess moisture, the wood can
subsequently shrink, leading to job failure.

b. If a wood floor (solid, laminated or engineered) is

installed above wet concrete the wood can absorb
moisture emitting from the concrete causing
the wood to swell and buckle and even cause
structural damage to the building. For measuring
the moisture in concrete, the Tramex CME4 or
CMEXpert should be used.

c. Your MRH III can be used to measure the moisture

content of the wood floor to ensure it meets
specification. Likewise it can be used to check, on
a comparative basis, through the floor covering, to
identify elevated moisture in the substrate.

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NOTE:

On the Wood, Drywall, Roofing and Laminate Scales the
depth of penetration of the MRH III signal can be up to
1¼" (30 mm) When using any of these scales on wood
or laminate over concrete or other screeds, the MRH III
will be reading through the material and may be giving
a much higher than expected reading. This is invariably
due to the fact that concrete is a much denser material
than wood or wood-based products. In such instances,
the wetter areas can be identified non-invasively
and the wood probe can then be used to make select
intrusions to determine the moisture content of the
wood or laminate.

Specific Gravity Adjustment Table (SG > 0.80)

Reading

S.G. set at 0.5

5 to 9 -3 -4 -4 -4
10 to 12 -4 -5 -5 -5
13 to 15 -5 -6 -6 -6
16 to 18 -6 -7 -7 -8
19 to 21 -7 -8 -9 -10
22 to 24 -9 -9 -11 -11
25 to 27 -11 -11 -12 -13
28 to 30 -12 -13 -13 -14
31 to 33 -14 -14 -14 -15
34 to 36 -15 -15 -15 -16

0.85 0.9 0.95 1

SG

Adjustment

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Adhesives

The presence of different species, treatments,
adhesives, etc., within products such as plywood,
particleboard, OSB (oriented strand board), laminated
and engineered woods will affect measurements. If in
doubt please contact us and, if you wish, we can work
with you in developing your own calibration for a specific
product.

Concrete

Your MRH III is not calibrated for concrete. The Tramex
Concrete Encounter CME4, CMExpert and instruments
are specifically designed for concrete flooring and
are recommended where quantitative measurements
are required. However a comparative indication of the
moisture condition of a concrete or sub floor can be
obtained with the MRH III set on the Masonry scale.
Comparative readings can also be obtained through
coverings such as vinyl, carpet and laminated wood
flooring by using the Laminate Scale.

Chemical treatment or contamination

Readings may be affected by certain flame-retardants,
preservatives, aluminium paint and contamination by
salt water. Treat all readings on such wood as indicative
readings only.

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Table of Wood Specific Gravities (SG)

Hardwoods ( Am. = American )

Alder, Red (Am. Alder, Western Alder) Alnus rubra....................0.41

Ash, White (Northern / Southern Ash) F. americana.................0.60

Aspen, Quaking (Am. Aspen) Populus tremuloides...................0.38

Basswood (Am. Basswood, Linden) Tilia americana..................0.37

Beech Fagus Grandifolia.........................................................................0.64

Birch, Yellow (Gray, Silver, Swamp)B. alleghaniensis................0.62

Cherry (Am. Black Cherry) Prunus serotina...................................0.50

Cottonwood (Eastern Cottonwood) Populus deltoides..........0.40

Elm, Red (Slippery elm) Ulmus rubra................................................0.53

Hackberry (Common Hackberry) Celtic occidentalis...............0.53

Hickory (Pignut, True Hickory) Carya glabra..................................0.75

Maple, Am. Hard (Sugar Maple) Acer saccharum......................0.63

Maple Am. Soft (Red Maple) Acer rubrum....................................0.54

Maple, Silver Acer saccharinum.........................................................0.47

Maple, Black Acer nigrum......................................................................0.57

Oak, Northern Red Quercus rubra....................................................0.63

Oak, Southern Red (Cherrybark) Quercus falcata...................0.68

Oak, White (Am. White Oak) Quercus alba...................................0.68

Pecan Hickory (Am. Pecan) CaryaiIllinoensis..............................0.66

Red Gum (Sweetgum) Liquidamber styraciflua.........................0.52

Sassafras (Golden Elm) Sassafras albidum.................................0.46

Sycamore (Am. Planetree, Buttonwood) P. occidentalis.......0.49

Walnut, Black (Am. Walnut) Juglans nigra.....................................0.55

Willow, black (Am. Willow) Salix nigra............................................0.39

Yellow Poplar (Am. Tulipwood, Tulip Poplar, Canarywood)

Liriodendron tulipifera...........................................................................0.42

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Softwoods

Cedar, Alaska (Alaskan Yellow).............................................................0.44

Cedar, Incense...............................................................................................0.37

Cedar, Port-Orford......................................................................................0.43

Cedar, Western Red....................................................................................0.32

Douglas Fir, Coast.......................................................................................0.48

Douglas Fir, Interior West.......................................................................0.50

Fir, California Red.......................................................................................0.38

Fir, Grand.........................................................................................................0.37

Fir, Noble.........................................................................................................0.39

Fir, Pacific Silver..........................................................................................0.43

Fir, White.........................................................................................................0.39

Hemlock, Western......................................................................................0.45

Larch, Western.............................................................................................0.52

Pine, Lodgepole...........................................................................................0.41

Pine, Ponderosa .........................................................................................0.40

Pine, Sugar......................................................................................................0.36

Pine, Western White (Idaho)..................................................................0.38

Spruce, Englemann....................................................................................0.35

Spruce, Sitka.................................................................................................0.40

Exotic

Balsa .................................................................................................................0.16

Ebony.................................................................................................................1.10

Karri ..................................................................................................................0.82

Padauk ...........................................................................................................0.77

Tulipwood .....................................................................................................0.96

Note on specific gravity (SG): The specific gravity
(SG) of wood is the ratio of the density of wood to the
density of water at a specified temperature (generally
4ºC where the density of water is at its maximum). The
density of wood is usually based on the oven-dry weight
and the volume at the specified moisture content
(MC%), generally 12%.

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WOOD PIN METER MODE

Factors Affecting Moisture Readings

The readings of all moisture meters are influenced by
the characteristics of different species of wood as well
as temperature and other factors listed below.

Species

Different species of wood can vary in density and
conductivity, which can have an effect on the electrical
resistance of the wood. This can influence meter
readings for the same moisture content and can also
apply to similar species from different origins. A species
adjustment table is provided on page 30 to 41.

Temperature

Meter readings can be affected by wood temperature.
The Wood Probe is calibrated at 20°C (68°F). At wood
temperatures above 20°C (68°F), the meter readings
are higher and at wood temperatures below 20°C (68°F)
the meter readings are lower. A temperature adjustment
chart is provided on page 28.

Chemical treatment or contamination

Readings may be affected by certain flame retardants,
preservatives, aluminium paint and by contamination by
salt water. Treat all readings on such wood as indicative
readings only.

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Surface Moisture

Surface moisture due to wetting or condensation
can affect readings when uninsulated pins are used.
It is recommended that insulated pins such as SP-52
are used in conjunction with HA-22 Hammer Action
electrode. As the pins are driven into the wood, readings
can be taken at different depths, unaffected by
moisture on the surface.

Wood Flooring

Excess moisture in wood flooring can cause major
problems. For instance, if installed with excess
moisture, the wood can subsequently shrink leading
to job failure. If a wood floor (solid, laminated or
engineered) is installed above wet concrete the wood
can absorb moisture emitting from the concrete causing
the wood to swell and buckle and even cause structural
damage to the building.

Your MRH III in PIN Probe mode can be used to measure
the moisture content of the wood floor to ensure it
meets specification.

Testing wood and wood products

a. When testing wood, power-on, insert wood probe

into phono-socket at the top of the MRH III and
select Pin Probe Mode using the key.

b. When a wood probe is inserted the moisture

content (MC) in percent is shown on the righthand
side of the bottom line of the display.

c. If possible, always take readings with the pins

parallel to the direction of the wood grain.

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d. Calibration tests are based on Douglas fir, which

has a published specific gravity (SG) of 0.50.

e. Acceptable levels of moisture content depend on

climatic conditions and we advise you check the
levels acceptable in your area. The Table on page
19 shows the approximate relationship between
the ambient relative humidity and equilibrium
moisture content in woods.

f. The following moisture content levels are often

quoted in the wood industry and should be used as
a guide only. Please contact industry associations
and manufacturers for their specifications.

● Furniture: 5% to 6% when used in locations of low
relative humidity and up to 10% to 11% may be
acceptable where the relative humidity is higher.

● Interior wood: 6% in low humidity areas. Up to
12% in higher humidity locations.

● Exterior wood: 10% to 15% depending on local
humidity levels.

● Generally, wood with moisture content in excess of
23% to 25% is susceptible to rot.

● Wood moisture content in excess of 18% to 20%
may provide an environment for termite and
woodboring insects to thrive and multiply. Wood
at these high levels can also support mold and
biological growth.

● Wood at 28% moisture content is considered to
have reached fiber saturation point.

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g. Avoid taking readings on wood from the top of a

stack stored outside as these may be affected by
surface moisture from recent rain.

h. When taking readings in chemically treated wood,

it is advisable to allow for possible effects that the
treatment may have on readings.

Temperature Adjustment Chart

For use in pin-mode only.

The instrument has been calibrated on wood at an
ambient temperature of 20°C ( 68°F). When measuring
moisture in wood at a different temperature , the
following temperature adjustment needs to be applied.
(Figures rounded to the nearest whole number)

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Example 1:

If meter reads 15% and temperature of wood is 10°C
(50°F), actual moisture content is 17%.
i.e.15% + 2% = 17%

Example 2:

If meter reads 15% and temperature of wood is 50°C
(122°F), the actual moisture content is 11%.
i.e.15% - 4% = 11%

Combined Species / Temperature Correction

Example 1

If meter gives reading 15% on a sample of Sitka Spruce
and the wood temperature is 40°C, the correction is as
follows: Species correction @15% = 16%, Temperature
correction @ 40°C = - 3% Corrected reading: 13%.

Example 2

If meter gives reading 24% on sample of Teak and
the wood temperature is 10°C, the correction is as
follows: Species correction @24% = 20% Temperature
correction @ 10°C = + 2% Corrected reading: 22%.

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HUMIDITY MEASUREMENT MODE

The Hygro-i2 Probe utilises state of the art electronic
technology to provide an “easy to use” and accurate
method for measuring relative humidity, mixing
ratio, temperature and dew point in a wide range of
applications such as:

● Heating, ventilation and air conditioning (HVAC)
systems.

● Environmental and building monitoring.

● Building inspection.

● Flooring (including in-situ method as per ASTM
F2170 and the in-situ and hood methods as per
British Standards BS 8201, 8203, 5325.)

A typical MRH III display with the Hygro-i2 Probe is
shown below.

When the Hygro-i2 Probe is plugged into the MRH
III, the or key can be used for changing the
temperature between °C and °F and the mixing
ratio between g/kg and grains/lb.

Relative Humidity

T˚C

Dew-point (Td)˚C

Flashing "H" in Hold mode

IMPERIAL

Mixing Ratio g/kg

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Relative Humidity Measurement

There are two International Standard methods of
relative humidity measurement in flooring that can be
carried out with the MRH III with the Hygro-i2 probe
attached:

(a) In-situ (below the surface of the slab) ASTM F2170
and BS 8201, 8203, 5325.
(b) RH Hood (on the surface of the floor slab) BS 8201,
8203, 5325.

(a) In-situ Relative Humidity Test Method – ASTM
F2170 Guidelines.

● Perform 3 per first 1000ft² (100m²) and 1 per
next 1000ft². Holes must be drilled dry and
perpendicular (90°), do not use water for cooling or
lubrication.

● Hole depth, when drying is from the top only, it is
recommended that the hole should be drilled to
approx 40% of the slab thickness.

● When drying is from both sides, it is recommended
that the slab should be drilled to approx 20% of
slab thickness.

● A hole cleaning brush is often required to ensure
the drilled hole is free from any loose particles.
A vacuum should also be used to ensure the drilled
hole is free from any dust.

● The user should always refer to ASTM or national
standard guidelines for definitive and current
procedure and specifications.

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MOISTURE TESTING GUIDELINES

When performing moisture testing of concrete it is
important to get the most accurate and useful data
from the tests. For this reason, Tramex recommend a
two-pronged approach. The first step is to carry out a
non-invasive moisture test with the Tramex CME4 or
CMEX. This measures the top section of the concrete
slab and gives an average percentage moisture content
of the footprint area of the meter. These readings
should be used to determine where and how in-situ
relative humidity (RH) testing is performed. Tramex
recommend that the test holes are drilled, sleeves
are placed and capped and left for a period of time as
outlined in International Standards (British Standards:
72 hours. ASTM: 24hours) The probes are then inserted.
A suitable equilibration time is allowed before taking
readings (see below).

The above recommendations are based on the
requirements to prolong the life of the RH probe and to
increase the accuracy of the test. Tramex recommend
that the RH probes are not left in-situ for prolonged
periods of time when the RH values are above 93%.
With the Tramex system it is possible to remove the
probe and seal the sleeve for future testing, thus
giving a more reliable and accurate test.

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Equalibration Time:

Allow at least 30 minutes for probe to reach
temperature equilibrium before measuring
relative humidity. It is vitally important that the
concrete is at the same temperature as the probe.

Even a slight difference in temperature will
produce a significant error in relative humidity
measurement. Check that meter readings do not
drift by more than 1% RH over a 5 minute period.

The sensor in the Hygro-i2 probe may take longer
to recover if exposed to readings above 93% and
can be damaged by prolonged exposure to high
humidity.

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HOLE LINER INSTRUCTION ASTM F2170

a - Cap

b - Hole liner

d - Retrieval tool

Cut hole liner to match drilled depth.
Check cap fits.

Use supplied Retrieval tool to
position the probe into place.

1 2

c - insertion tool

3 4

Push hole liner
to bottom of
drilled hole.

5 6

Drill a ¾" hole to required depth.

Should the hole
liner require
additional sealing
at the opening
please consider
the application
of a Butyl-based
sealant.

Connect with
Tramex
Electronic
Interface

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RH Hood Method

1

3

5

Seal cap

Hygro-i2 probe

Hygrohood

Place the probe in the RH hood.

Press down the cap
to seal

Connect your
Tramex Meter
to take readings

Ensure the surface is clean

2

to achieve an airtight seal

Seal the Hygrohood to the
surface with butyl tape provided

Leave the Hygrohood in place

4

for the period of time
specified by the standard
being followed.

A probe calibration check, is

6

recommended within

30 days of testing

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(b) On surface RH tests (RH hood method)

The Tramex RH Hood can be used to perform testing to
British Standards BS 8201, 8203, 5325. The following
components are required to perform a RH Hood test:
MRH III, Insulated hood (RHIH), Hygro-i2 probe and
interface. The Tramex CMEX II or WME can also be used
with the RH Hood.

Pre test guidelines

The Tramex CME4 or CMEX II should be used first in
non invasive mode to give an overall moisture condition
of the floor slab. These readings will determine where
to position the insulated hood. Careful consideration
should be given to location of test site. The hood should
not be located in direct sunlight or in an area which can
be accidently disturbed. The floor slab surface should
be cleaned of any foreign materials and swept clean of
any dust or loose materials that could affect a proper
seal between the hood and surface of the floor.

1. Using a double-sided preformed adhesive/butyl
tape, seal the insulated RH hood to the concrete
surface.

2. Insert Hygro-i2 probe into the hood using the
insertion/ retrieval tool.

The sensor in the Hygro-i2 probe may take longer
to recover if exposed to readings above 93% and
can be damaged by prolonged exposure to high
humidity.

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3. Please refer to the period of time as specified by
the standard being followed for the duration of
the test. The user should always refer to national
standard guidelines for definitive and current
procedures and specifications.

4. When the time period has elapsed, check
that meter readings do not drift by more
than 1% RH over a 5 min period.Ensure the
readings correspond with the floor covering/
adhesive manufacturers or national standard
recommendations before applying floor covering.
e.g. British standards code of practice BS8203
suggests that a concrete floor should be
sufficiently dry to allow installation of a resilient
floor covering when the measured relatively
humidity falls to 75% or lower using the using
the insulated impermeable box/hood method as
specified in the above standard.

Use of artificial aids for accelerated drying of
concrete is not recommended. If they are being
used it is recommended that they be turned off
at least four days before taking final readings.

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CALIBRATION CHECK SALTS

A saturated salt solution is the most suitable method
for on-site testing of humidity sensors. The advantage
of the on-site salt calibration check is that the user can
check that the sensors are performing satisfactorily
without having the need to send the sensors to a testing
laboratory, which can be expensive and time consuming.
The sensors can be checked at a time that is convenient
to the user, which means no down time for your
equipment. ASTM F2170 requires that humidity probes
are checked and readings recorded by the user within
30 days before use. This check can be achieved with a
75% RH saturated Sodium Chloride (NaCI) solution.

Conditioning of the NaCI calibration check solution
and test procedure.

As Relative Humidity (RH) is defined as the ratio of
the partial vapor pressure in air to the saturated vapor
pressure at a given temperature, it is important to
understand that RH strongly depends on temperature.
Therefore, it is essential to keep humidity sensors at
the same temperature as the air in which the relative
humidity is to be measured. When testing RH probes
in a calibration check-salt chamber, it is necessary for
the internal temperature of the salt chamber to be the
same as that of the surrounding air and also the RH
probe sensor. This can be achieved by removing the
cap and exposing the salt-check solution to ambient
conditions. The temperature can be checked with the
use of an infra red thermometer. When the probe and
solution are showing equal temperature insert the
probe into the solution.

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The test can be ended when RH% readings do not drift
by more than 1% RH over a 5 minute period within
the acceptable +/- 2% tolerance of the nominal 75%
relative humidity. A temperature difference of +/- 1°C
(1.8°F) can cause an error of up to +/-3 to 5% at 50%
RH and +/-6% at 97% RH readings. Please note any
further handling of the salt chamber can cause a heating
effect so handle the salt chamber as little as possible.

Due consideration must also be given to the test site,
do not perform in direct sunlight or close to sources of
heat eg. heaters or spotlights.

Temperature stability is extremely important for the
duration of the test.

Calibration check salts do not have an expiry date and
have unlimited usage when cared for in the correct
manner.

Do check the seal inside chamber is exposing as much
of the vent as possible and that there is a mix of salt and
water and no caking of salt to side walls of chamber.

Humidity probes exposured to conditions outside
normal range, especially high humidity may temporarily
offset the RH reading. After return to normal ambient
condition it will slowly return towards calibration state
by itself. Prolonged exposure to extreme conditions
may accelerate ageing.

For further information please refer to the latest
calibration check salt instructions which are supplied
separately.

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LIMITATION

The MRH III will not detect or measure moisture through
any electrically conductive materials inculding metal
sheeting or cladding, many types of black EPDM rubber
or wet surfaces. The MRH III is not suited for taking
comperative readings in the concrete substrate through
thick floor coverings such as wood.

CALIBRATION

For regular on-site assesment your MRH III in moisture
measurement mode, calibration-checks are available
from the suppliers of your MRH III. Should it be
found that readings are outside the set tolerances,
it is recommended that the MRH III be returned for
recalibration. Calibration adjustments should not
be carried out by anyone other than Tramex or their
authorised service provider who will issue a calibration
certificate on completion. Requirements for quality
management and validation procedures, such as ISO
9001, have increased the need for regulation and
verification of measuring and test instruments. It is
therefore recommended that calibration of the MRH III
should be checked and certified in accordance with the
standards and/or protocols laid down by your industry
(usually on an annual basis) by an authorized test
provider. The name of your nearest test provider and
estimate of cost is available on request.

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WARRANTY

Tramex warrants that this instrument will be free from
defects and faulty workmanship for a period of one year
from date of first purchase. If a fault develops during the
warranty period, Tramex will, at its absolute discretion,
either repair the defective product without charge for
the parts and labour, or will provide a replacement in
exchange for the defective product returned to Tramex
Ltd. This warranty shall not apply to anny defect, failure
or damage caused by improper use or inadequate
maintenance and care.

In no event shall Tramex, its agents or distributors be
liable to the customer or any other person, company or
organisation for any special, indirect, or conseqential
loss or damage of any type whatsover (including without
limitation, loss of business, revenue, profits, data,
savings or goodwill), whether occasioned by the act,
breach, omission, deafult, or negligence of Tramex Ltd.,
whether or not foreseeable, arising howsoever out of
or in connection with the sale of this product including
arising out of breach of contract, tort, misinterpretation
or arising from statute or indemnity. Without prejudice
to the above, all other warranties, representations
and conditions whether made orally or implied by
circumstances, custom, contract, equity, statue or
common law are hereby excluded, including all terms
implied by Section 13, 14 and 15 of the Sale of Goods
Act 1893 and Sale of Goods and Supply of Services Act

1980.

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Warranty claims

A defective product should be returned by shipping pre
paid, with full description of defect to your supplier or to
Tramex at address shown on the back of this guide.

PRODUCT DEVELOPMENT

It is the policy of Tramex to continually improve and
update all its products. We therefore reserve the right
to alter the specification or design of this instrument
without prior notice.

SAFETY

This Users guide does not purport to address the safety
concerns, if any, associated with this instrument or its
use. It is the responsibility of the user of this instrument
to establish appropriate safety and health practices and
determine the applicability of regulatory limitation prior
to use.

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