Maximum Weather Instruments Professional 2S-B-S-O, Professional 2S-C-S-O, Professional-B-B-M, Professional 2S-B-B-O, Professional 2S-B-S-M User manual

MAESTRO

INSTALLATION

PROPER INSTALLATION IS IMPORTANT. IF YOU NEED ASSISTANCE, CONSULT A CONTRACTOR, ELECTRICIAN

OR TELEVISION ANTENNA INSTALLER (CHECK WITH YOUR LOCAL BUILDING SUPPLY, OR HARDWARE STORE

FOR REFERRALS). TO PROMOTE CONFIDENCE, PERFORM A TRIAL WIRING BEFORE INSTALLATION.

T-4

(S & SW)

BOSS

T-5

(W & NW)

5

BOOT

WIND DIRECTION

SENSOR

TERMINAL

#3

TERMINAL #3

MUST ALIGN

WITH Z-MAST

ARM

T-3

(POWER)

RED

SLEEVE

4

2

1

3

1

Determine where you are going to locate both the
rooftop sensors and the read-out.

Feed the teminal lug end of the 2-conductor cable through one
of the rubber boots and connect the lugs to the terminals on the
bottom of the wind speed sensor. (Do NOT adjust the nuts
that are already on the sensor). The polarity does not matter.

T-2

(E & SE)

TERMINAL-1

(N & NE)

3

Feed the terminal lug end of the five-conductor
cable through the other rubber boot and connect
the lugs to the terminals on the bottom of the wind-direction
sensor. (Do NOT adjust the nuts that are already on the sensor).
The red sleeve indicates wire #1.

5-CONDUCTOR

CABLE

Slide the stub masts through the rubber boots and

4

insert the stub masts into the bottom of the sensors. Secure
with the cotter pins. Coat all wire connections with silicone
sealant and slip the boots over the sensors.

BOSS

4A

When assembling the wind direction sensor
to the Z-mast, make certain that terminal #3
is aligned with the Z-mast arm.

2

WIND SPEED

SENSOR

STRAIGHT

STUB MAST

2-CONDUCTOR

CABLE

COTTER

PIN

2-CONDUCTOR

CABLE

BOOT

WIND DIRECTION

SENSOR

COTTER

PIN

Z-STUB

MAST

5-CONDUCTOR

CABLE

BOOT

Secure the sensors and stub masts to your antenna mast (not supplied) with

5

the two hose clamps. Align the wind-direction Z-mast arm to true North.
Radio Shack and similar stores have a selection of tall masts and roof
mounting brackets. Choose a mount that best suits your location and
provides at least eight feet of vertical clearance above objects on the roof.

NORTH

HOSE

CLAMPS

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TRIPOD
MOUNT

CHIMNEY

MOUNT

MAESTRO

INSTALLATION

(continued)

WALL

MOUNT

EVE

MOUNT

8 FEET

VENT-PIPE

MOUNT

6

Follow the instructions supplied with the antenna
mount and secure the mast to the mount.

7

Secure the wire to the building using cable clips (do not use regular
staples). Form a drip loop where the wires enter the hole drilled
through the exterior wall. Caulk the hole when done.

Feed the cables through the wall to where the read-out is going to

8

be located. Attach the wires to the rear of the read-out as shown.
The direction wires must follow in sequence for the direction sensor.
The polarity does not matter for the wind speed or power supply
connections. (Do NOT adjust the nuts that are already on the meter).

CABLE

CLIPS

CAULK

WIRE

DRIP

LOOP

2-CONDUCTOR

2-CONDUCTOR

CABLE FROM

AC POWER

SUPPY

5

4

3

2

1

5-CONDUCTOR

CABLE FROM

WIND-DIRECTION

SENSOR

CABLE FROM
WIND-SPEED

SENSOR

Mount the brass read-out directly over the cable feed-thru-hole
to avoid crimping the wire under the lip. We recommend mounting
the read-out on one of our pre-drilled and centered panels. Plug the
power supply into a 110 VAC power outlet.

CABLE-HOLE

9

WALL

CABLES

WOOD
PANEL

CABLE-HOLE

CABLES

SCREW

SCREW

SCREW

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MAESTRO

OPERATION

To reset the gust register needle,
turn the knob counter-clockwise.

Turning the knob counter-clockwise
will eventually contact the gust register.
The Gust Register should not be set under 15 MPH - this
gives the needle room to operate at low speeds. If the
Gust Register is set below 15 MPH turn the knob
clockwise until the needle registers greater than 15 MPH.

After setting the Gust Register turn the
knob clockwise until the reset arm is
parked near the six o'clock position.
Failure to do so may damage your
meter.

WIRE

GAUGE

24
22
20
19
18

The wind direction may be read with 16-point
accuracy. In this example both the NE and the
E indicator lamps are illumitated. This would
be read as East-Northeast.

ADDITIONAL INFORMATION

Cables can be shortened or lengthened without affecting accuracy

WITHOUT RECALIBRATION

(supplied with instrument)

MAXIMUM FEET

300'
500'

750'
1000'
1250'

WIRE

GAUGE

16
14
12
10

MAXIMUM FEET

WITHOUT RECALIBRATION

2000'
3200'
5000'
8000'

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MAESTRO

TROUBLE SHOOTING

Maximum Instruments are accurate and reliable. Most problems that occure are

due to loose or corroded connections. If, after checking the connections, there is

still a problem, determine if the problem is with the sensor or the brass read-out.

WIND SPEED

1. Disconnect the two wind-speed wires from the back of the brass read-out.

2. Attach a low range AC Analog Voltmeter to the wires. If the speed sensor is operating

properly, you will achieve these approximate readings: 8-9 MPH = 0.28 VAC rms,
17 MPH = 0.56 VAC rms, 51 MPH = 1.78 VAC rms, 102 MPH 3.67 VAC rms

3. If the speed sensor delivers these approximate readings, t
is faulty. If the speed sensor does not produce these readings, then either the
speed sensor or the wire is faulty.

WIND DIRECTION

hen the brass read-out

1. Unplug the AC Power Adaptor.

2. Disconnect the AC Adaptor wires and the 5-conductor cable

of the brass read-out.

3. Connect an AC Voltmeter to the two wires coming from the A

4. Plug in the AC Power Adaptor to a 110 VAC outlet. When fu
the adaptor will deliver 11.5-18 VAC. If the adaptor checks out fine,
further with the test. If not, send both the adaptor and the instrument to Maximum.

5. If the AC Adaptor checks okay, unplug the Adapter and re-c
to the back of the brass read-out.

6. Plug in the AC Power Adapter.

7. Using a small piece of wire or a paper clip as a jumper,
(the middle one of the five). Touch the other end to terminal #1, then #2, then #4 and
lastly #5 (keeping one end of the jumper on terminal #3). At each termial, two adjacent
lights should light up simultaneously. If any light fails to function properly, the fault
lies within the brass read-out.

8. If all the lights function properly, then the problem lies
outdoor wind direction sensor. Disconnect the wires at the sensor and bring it down to
the brass read-out.

9. Use a short piece of the 5-wire cable and reconnect the se
shown in the installation instructions.

10. Rotate the vane slowly by hand and observe the lights on t
operate properly, then the installed wiring is at fault; if not, then the outdoor wind
direction sensor is faulty.

with either the wiring or with the

wires from the back

C Power Adaptor.

nctioning properly,

proceed

onnect the two wires

touch one end to terminal #3

nsor to the brass readout as

he brass read-out. If they

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IMPORTANT ADDITIONAL INFORMATION

Components: Along with the indicator, the following components are included with this instrument:

Rooftop sensors: To insure a clear unobstructed path for the wind to the sensors, they should be

mounted on some type of antenna mast at least 8-10’ above the highest object on your roof.
Remember, your roof is also an obstruction and it usually requires at least 8’ of height to avoid the
turbulence it creates.

AC Adaptor: This instrument requires its own AC Adaptor. Due to the various power

requirements of each Maximum instrument, attempting to run more than one instrument on a single
adaptor could cause improper operation and/or damage to the instrument(s) thereby voiding your
5-year warranty.

Sensors: Properly installed, your sensors will require virtually no maintenance at all. Our sensors

do not utilize brushes or wiping contacts. All bearings are Rulon-J self lubricating type and will
perform for many years in the harshest environments.

Brass Case: Your brass case is solid brass A70-30 Holloware quality, with a durable lacquer

finish. It is in fact a piece of jewelry and should be treated as such. It should be cleaned at least
once a week to keep airborne pollutants (dust, etc…) and any moisture from collecting on the case
thereby attacking the lacquer. At no time should you use an abrasive cleaner or cloth on the brass
case. Simply use a soft cloth or soft paper towel with a mild glass cleaner to wipe the case clean.
If your instruments are in a summer home, and you are not able to clean them regularly, simply lay
a small cloth or towel across the top two-thirds so that dust cannot settle on the finish.

Specifications: All instrumentation or measuring devices have accuracy tolerances and

specifications. Making comparisons between different pieces of equipment is appropriate provided
the specified accuracies of both are known.

Measurement Range Guaranteed Accuracy

Wind Speed 0-100 MPH ±3% Full Scale & Mid Scale
Wind Direction (Indicator) 16 Compass Points Zero Error (Digital Display System)

Wind Direction (Sensor) ±11.25 Degrees

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Electrical Da

mage – Common Causes & Recommended Prevention

Electrical damage can be caused by many different factors. Below are some of the more common causes and
some suggested methods of minimizing potential problems.

Common Causes:

 Storm Activity – lightening in your area can do damage to your instruments in different ways. The obvious

way is due to a direct or nearby strike. In addition, lightening storms, dust storms, dry snowstorms and
strong dry winds can all cause static electricity to build up on and around your external sensors. Rega rdless
of the cause this built up electricity can discharge itself through the cable connecting the external sensors to
the instrument.

 Power Surges – A surge may come from the electric company’s switching generators or power grids, from

local industries or after power interruption when accumulated power suddenly surges back through AC lines.
Even the on-and-off switching of large electrical appliances, such as refrigerators or clothes dryers can
create damaging fluctuations. This is especially true with sensitive weather recording devices.

 Yourself – Are you constantly giving and/or receiving a shock every time you touch a doorknob or another

person? If so you have a great deal of static electricity in your environment. Depending on where you live,
static electricity may be a year round problem or only a seasonal problem. In either case, it is possible for a
person to carry enough of a charge to damage an instrument.

Recommended Prevention:

Ground Your Mounting Mast – IMPORTANT: PVC and fiberglass are not recommended

mast materials as
they can store high amounts of static electricity within themselves. It is recommended that you follow the
grounding instructions that came with your mounting mast, while also maintaining accordance to your local
Electric Code. In the absence of instructions for your mast system, the following generic guidelines from the

ational Electric Code may be helpful.

N

1) The NEC requires that the antenna mast and mount be grounded directly. No splice s or connections are
allowed in the ground wire between the mast and the ground rod.

2) Attach one end of a No. 8 (or thicker) copper or aluminum ground wire to the antenna mast. Note: As static
electricity issues are more common for weather sensors than direct lightening strikes, consider installing the
ground wire as physically close to the wind sensors as possible to best combat static ele ctricity issues. For
multi-piece (or telescoping) masts, consider connecting the ground to each separate section of the mast.

3) For painted or coated masts, scrape off the coating around the area where the contact will be made. This
will ensure a good, solid connection. (Once the ground is attached to the mast, any scraped off portion that
is exposed should be recoated with paint or other sealant.)

4) Next, run the ground wire to ground as directly as possible. Standard wire staples can be used to secure the
ground wire against the side of the house. Avoid making 90° or sharper turns with the ground wire. A
lightning charge has difficulty making such a turn and therefore may discharge into the house. Make ground
wire bends as smooth and as gradual as possible.

5) The ground wire must be connected to a ground rod. Water pipes or plumbing fixtures are not acceptable.
A good copper-coated steel ground rod driven at least 3 feet into the ground is required. Special clamps that
provide a solid connection between the ground wire and ground rod should be used

 Use Surge Protectors – For the AC adapter, a UL 1449 rated surge protector with EMI/RFI filtering is

recommended. This rating will be clearly listed on the packaging of any good quality surge protector.

 Discharge Yourself – If the instruments are located in an environment where static electricity is a proble m ,

make sure that you discharge yourself before touching the instrument(s). The shock that you get from
touching a doorknob or another person can often be sufficient to damage an instrumen

t.

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MINI-MAX

INSTALLATION

PROPER INSTALLATION IS IMPORTANT. IF YOU NEED ASSISTANCE, CONSULT A CONTRACTOR, ELECTRICIAN

OR TELEVISION ANTENNA INSTALLER (CHECK WITH YOUR LOCAL BUILDING SUPPLY, OR HARDWARE STORE

FOR REFERRALS). TO PROMOTE CONFIDENCE, PERFORM A TRIAL WIRING BEFORE INSTALLATION.

Mount the temperature sensor assembly with the two

1

WOOD

SCREWS

large wood screws. Select a location that is protected
from direct sunlight and sheltered. (A north exposure, six
feet above the ground will give the best results.)

CAULK

8"

MIN

CABLE

CLIP

DRIP

LOOP

Mount the Brass Readout directly over the Feed-Thru-Hole
to avoid crimping the wire under the lip. We recommend
mounting the Readout on one of our pre-drilled and
centered panels.

TEMPERATURE

GREEN

GROUNDING

CORD

AC

ADAPTOR

2

Form a drip loop with the wire at least eight inches
below the exit from the sensor and at least eight inches
below the point of entry into the building. Anchor any
exposed wire with insulated cable clips. Run the wire
through the building to the location where the indicator
will be located. Caulk any holes when done.

TO

SENSOR

Feed the AC Adaptor Cord, Green Grounding Cord and Sensor

4

wire to the Indicator. Connect the two temperature sensor wires
to the appropriate terminals (HEX NUTS) as shown in the
illustration. The polarity does not matter. Connect the AC adaptor
wires to their appropriate terminals (HEX NUTS) as shown in the
illustration. The polarity does not matter for these.

CABLE-HOLE

3

WALL

PRE-DRILLED PANEL

SCREW

SCREW

To prevent static from causing bad readings it is necessary to
"EARTH GROUND" you Mini-Max. Proceed as follows:

-Turn off the circuit-breaker to the outlet where the ground cord
is attached.

-Remove the outlet cover screw.

-Insert the outlet cover screw through the lug on the green
grounding cord and reinsert the outlet cover screw.

-Turn on the circuit-breaker to the outlet.

-Plug in the AC Adaptor.

-Reset the memories as described in the operating instructions
(next page).

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5

GREEN

GROUNDING

CORD

LUG

SCREW

MINI-MAX

OPERATION

Your Mini-Max II has two switches. The toggle switch is for selecting the function. The small push button
switch behind the toggle is for resetting the memories.

Lightly holding the toggle switch to the

1

left will display the recorded low
temperature since the last reset.

Lightly holding the toggle switch
to the right will display the recorded
high temperature since the last reset.

Fully depressing the small push button switch for five seconds resets

3

both memories. The instrument will now display current temperature
and the memories once again begin storing the new high and low
temperatures.

(After resetting wait 10 seconds before activating the toggle switch.)

NOTE: Before reading your
thermometer, you should
lightly tap the case with
your finger. A TAP change
of 1-2 degrees is a common
occurance with any slow moving
precision meter movement.

2

4

The trend register needle can be set by turning the center
knob on the indicator dial.

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MINI-MAX

TROUBLE SHOOTING

1

3

4

5

Unplug the AC adaptor and remove the instrument from the wall.

Disconnect the AC adaptor from the indicator and connect
it to an AC Voltmeter. Plug the AC adaptor back in.

If working properly the AC adaptor will deliver 11.5 to 18VAC.
If not working properly please contact the factory. If the AC
adaptor is working properly, continue with the next steps.

Unplug the AC adaptor and reconnect it to the indicator.
Plug the AC adaptor back into a 110V outlet.

Disconnect the sensor wires from terminals #1 and #2 on the back of the indicator. The indicator
pointer should drop to -35 F or below.

AC

ADAPTOR

AC

VOLTMETER

2

Use a jumper wire (a paper clip will do) to connect

6

Use a jumper wire to connect across terminals #2 and #3. The
calibration test point has been hand-written on the back of the
indicator just above terminals #2 and #3. If the indicator is in proper
working order it will read within 2 F of this number. We recommend
that you re-mount the instrument in this mode for several hours and
observe it periodically. This will help to detect most intermittent
problems. If the indicator registers within 2 F of the test point, then
the problem is in the sensor or wire.

across the sensor terminals #1 and #2. The indicator
should read 120 F. If so, disconnect this jumper and
proceed to the next step.

7

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IMPORTANT ADDITIONAL INFORMATION

Components: Along with the indicator, the following components are included with this instrument:

AC Adaptor: This instrument requires its own AC Adaptor. Due to the various power

requirements of each Maximum instrument, attempting to run more than one instrument on a single
adaptor could cause improper operation and/or damage to the instrument(s) thereby voiding your
5-year warranty.

Brass Case: Your brass case is solid brass A70-30 Holloware quality, with a durable lacquer

finish. It is in fact a piece of jewelry and should be treated as such. It should be cleaned at least
once a week to keep airborne pollutants (dust, etc…) and any moisture from collecting on the case
thereby attacking the lacquer. At no time should you use an abrasive cleaner or cloth on the brass
case. Simply use a soft cloth or soft paper towel with a mild glass cleaner to wipe the case clean.
If your instruments are in a summer home, and you are not able to clean them regularly, simply lay
a small cloth or towel across the top two-thirds so that dust cannot settle on the finish.

Specifications: All instrumentation or measuring devices have accuracy tolerances and

specifications. Making comparisons between different pieces of equipment is appropriate provided
the specified accuracies of both are known.

Measurement Range Guaranteed Accuracy

Temperature (Indicator) -35 to 120°F ±.5°C., 1°F

Temperature (Sensor) ±.5°C., 1°F

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Electrical Damage – Common Causes & Recommended Prevention

Electrical damage can be caused by many different factors. Belo
some suggested methods of minimizing potential problems.

Common Causes:

 Storm Activi

way is due to a direct or nearby strike. In addition, lightening storms, dust storms, dry snowstorms and
strong dry winds can all cause static electricity to build up on and around your external sensors. Rega rdless
of the cause, this built up electricity can discharge itself through the cable connecting the external sensors to
the instrument.

 Po

 Yourself – Are you con

wer Surges – A surge may come from the electric company’s switching generators or power grids, from
local industries or after power interruption when accumulated power suddenly surges back through AC lines.
Even the on-and-off switching of large electrical appliances, such as refrigerators or clothes dryers can
create damaging fluctuations. This is especially true with sensitive weather recording devices.

person? If so, you have a great deal of static electricity in your environment. Depending on where you live,
static electricity may be a year round problem or only a seasonal problem. In either case, it is possible for a
person to carry enough of a charge to damage an instrument.

ty – lightening in your area can do damage to your instruments in different ways. The obvious

stantly giving and/or receiving a shock every time you touch a doorknob or another

Recommended Prevention:

 Use Surg

recommended. This rating will be clearly listed on the packaging of all good qualit y surge protector.

 Discha

make sure that you discharge yourself before touching the instrument(s). The shock that you get from
touching a doorknob or another person can often be sufficient to damage an instrument.

e Protectors – For the AC adapter, a UL 1449 rated surge protector with EMI/RFI filtering is

rge Yourself – If the instruments are located in an environment where static electricity is a problem,

w are some of the more common causes and

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INSTALLATION/OPERATION

COMFORTMINDER

INSTRUCTIONS

INTRODUCTION:

Please read these instructions carefully before installing your COMFORTMINDER indicator. We have prepared
them carefully, knowing that some owners will use this instrument in a variety of areas for a variety of purposes –
greenhouse control, central air conditioning and heat monitoring, furniture protection, general comfort conditions
etc.

INITIAL ACTIVATION (HUMIDITY):

Before installation, place your indicator with its face down on a soft surface so as not to scratch the finish. Locate
a cloth, such as a dish towel or face cloth, wet it and wring it out so it is not dripping wet and lay it over the back
of the indicator for at least one half hour. Do not be concerned with the relative humidity reading at the end of
this time. Wipe any residual moisture off the back of the indicator when removing the cloth.

This procedure should only have to be done once, unless the COMFORTMINDER is to be used in areas of
persistently low humidities – that is, long periods where humidity is less than 40-45% RH. Once this activation
procedure is completed it may be several hours before COMFORTMINDER settles out to actual room conditions.

We include this initial “activation process” in our instructions because we often do not know where your
instrument has been and for how long, prior to your purchase. This procedure is for the humidity portion of
COMFORTMINDER only, and will not affect the temperature element or damage it.

INSTALLATION:

Your COMFORTMINDER indicator is easy to install. It is the actual location of the indicator that should take
some consideration. Simply put, the humidity sensing element of COMFORTMINDER is an absorption rather
than an evaporative device. Therefore actual air circulation is not vital to accuracy, but it will enhance response
rate.

The temperature element is a durable high quality Bi-metallic spring which is thermally coupled to the instrument
housing to attain as closely as possible, the average temperature in the area being monitored. Keeping this
information in mind, try to locate the indicator on a wall that will demonstrate, as closely as possible, the average
temperature and humidity in the area that is to be monitored – not on a cold outside wall or a wall with a heating
pipe or vent behind it or under it.

COMFORTMINDER can be mounted outdoors if it does not come in direct contact with moisture – spray, rain,
etc. Nor should it be used in direct sunlight, which could cause erroneous temperature readings. Place indicator
on the wall you have chosen and using the supplied brass screws, fasten to surface but do not snug down tightly.
Your indicator is designed to be spaced slightly off the wall. This space is controlled by the three spacers
mounted on the back of the indicator. These spacers, not the lip of the indicator, will make contact with the wall.
Once mounted, this space will hardly be noticeable.

HELPFUL COMMENTS & INFORMATION

* Lightly tap the instrument when reading.
* COMFORTMINDER should net need any maintenance (regeneration) unless as

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stated earlier, it is to be used in areas of persistent low relative humidities. If
COMFORTMINDER is subjected to such conditions, periodically follow initial
activation instructions. This procedure does not apply to nor will it affect the
temperature portion of COMFORTMINDER.

* COMFORTMINDER is measuring the relative humidity and temperature at the

location of the indicator, not at the local weather forecasting station. Relative
humidity and temperature, like many other elements, can be drastically different
with the smallest change of location.

* Your COMFORTMINDER case is jewelry quality brass with a durable finish. Do

Not clean with abrasives.

* Attempts to alter calibration will only destroy the eleme nts and void your 5-year

warranty.

Because humidity is the least understood and most difficult function of our environment to measure accurately,
the following essay should be carefully read to help you use and understand your COMFORTMINDER.

UNDERSTANDING HUMIDITY MEASUREMENT

A commonly asked question is, “why does my COMFORTMINDER read a different humidity than the weather
service, or another hygrometer in my home?” To adequately answer this question we must first explain a little
about humidity measur ement.

Humidity is defined as the amount of water vapor present in the atmosphere. The simplest way of expressing
humidity is as the absolute humidity. Absolute humidity is the density of water vapor, or the mass of the vapor
divided by the volume. The problem with this form of measurement is that it can vary as much as five orders of
magnitude (i.e. 1 to 100,000) over the surface of the earth at any point in time. Because of this large variation,
absolute humidity is not a useful form of measurement to most people.

A number of other measurements of humidity have been defined to correlate natural phenomenon with humidity.
Specific humidity is the ratio of the mass of water vapor to the mass of natural air. This form of measurement is
useful because it has less variation and is independent of temperature and barometric pressure (altitude). Specific
humidity is often used to relate the different forms of humidity measurement.

Relative humidity is by far the most popular form of humidity measurement. By definition, relative humidity is
the ratio of the measured vapor pressure to the maximum possible vapor pressure at the measured temperature. In
simpler terms, if the relative humidity is 50% then the air is holding 50% of the maximum amount of water vapor
possible at that temperature. Relative humidity is the measurement of humidity that most closely relates to
natural phenomenon. Some examples are, the changes in organic substances (i.e., the shrinking and swelling of
wood), the performance of electronic devices, and the level of comfort that we feel.

It was stated previously that specific humidity is independent of temperature and pressure. Relative humidity,
however, is dependent on temperature and pressure. Therefore, the relationship between specific and relative
humidities is governed by temperature and pressure. In general, barometric pressure doesn’t vary over small
areas. Also, of the two variables, pressure and temperature can vary greatly in a small area. Therefore, we will
only consid er the effect of temperature on the specific versus relative humidity relationship.

You can convert one version of humidity measurement to another by using complex mathematical formulae, a
table or a chart. A typical chart, known as a psychrometric chart, relates all of the basic humidity measurements.
We have included a simplified chart to facilitate comparison of specific and relative humidities.

Generally, the specific humidity in a small area (i.e., inside a building or around a yard) is constant. This is due to
the fact that most substances in the atmosphere (i.e., smoke, water vapor) tend to disperse evenly throughout the
air mass by a process called diffusion. Additionally, the specific humidity tends to be fairly constant from outside

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to inside a building. Because relative humidity is dependent on temperature, the relative humidity will vary in a
small area even though the specific humidity is not varying. A few examples will help illustrate this point.

In a building, we measure the temperature and relative humidity in one location to be 75 degrees F and 50% RH,
respectively. Referring to the psychrometric charts, we locate 75 on the bottom scale. We then follow the line
vertically up to the intersection with the 50% RH curve. From this point, we move horizontally to the right and
read the specific humidity as approximately 64 gr./lb. (grains of moisture per pound of natural air). We then
measure the temperature in another location within the building and find it to be 70 degrees. Now, assuming the
specific humidity to be constant, we can find the relative humidity at the new location. On the chart, we find the
intersection of the 70-degree line and the 64 gr./lb. line. This point is on the 60% RH curve. So, if we were to
place a hygrome ter in the new location it would read 60% RH. An indoor temperature variation of 5 degrees is
not uncommon. In many buildings we have measured 20-degree variations from one area to another. This shows
that within a building, 10% RH variations are common and 50% RH variations are possible.

Let us examine some indoor to outdoor variations. The local weather service reports that the temperature is 40
degrees F and the humidity is 60% RH. Using the chart, we find specific humidity to be 25 gr./lb. If the
temperature inside is 68 degrees F then, from the chart, the indoor relative humidity will be about 25%. This
example illustrates why it feels so dry inside during the cold winter months.

Next, let us assume that the weatherman says it is 90 degrees F and 50% RH outside. And because your home is
in the shade, your indoor temperature is 80 degrees F. Referring to the chart, we find the specific humidity to be
106 gr./lb. which, at the indoor temperature of 80 degrees, will yield an indoor humidity of 70% RH.

The previous examples show that if the specific humidity remains constant, then as the air temperature increases,
the relative humidity decreases. Conversely, as the air temperature decreases, the relative humidity increases.
This phenomenon explains why cellars tend to be wetter and attics tend to be drier than the rest of a building.

In modern buildings there are many factors besides air temperature that can influence humidity readings. One
factor is the material used in the construction of the building. Many common building materials (i.e. wood,
plaster, concrete) absorb and then release water vapor as the humidity varies. This causes the specific humidity to
vary, which in turn causes the relative humidity to vary. Probably the single bigge st factor affecting the humidity
is heating and air conditioning systems. A heating system can increase or decrease the specific humidity. Air
conditioning systems cause a decrease in the specific humidity. This decrease is because the cooling element in
an air conditioner is very cold. From the chart, you can see that as air passes by the very cold element, its relative
humidity increases rapidly. When the relative humidity reaches 100%, the water vapor condenses to liquid water.
The removal of vapor by condensation causes a drop in the specific humidity.

Another factor affecting the indoor humidity is that many newer buildings incorporate humidifiers and/or
dehumidifiers into the heating and air conditioning systems. We have had a number of custome rs who question
why their hygrometers never change more than 10% RH. When we check the instrument calibration, we find it
accurate. We then contact the customer and find out that their home has climate control. So, as it turns out, their
hygrometer is simply indicating that their control system is controlling the relative humidity very well. The
hygrometer, then, is a good indicator that all is well with their climate control systems.

With all of the aforementioned variables affecting humidity measurement, one might wonder, “How will I ever
know if my hygrometer is reading correctly?” Well, there is an acceptable method of checking hygrometer
accuracy that applies to all hygrometers.

First, you should place the instrument on a non-absorbent surface (i.e. glass or plastic, not wood) in the center of a
small room. You should leave the unit there at least two hours before proceeding. Next, you must obtain an
accurate instrument to compare against. The only commercially available instruments accurate enough to
compare against are:

Instrument Type Accuracy Approximate Cost

Sling Psychrometer +2.3% RH $40-80
Aspirated Psychrometer +1-2% RH $100-200
Chilled Mirror Dewpoint +0.5% RH $1,000-5,000

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Because of the high cost of the other two types of instruments, we will consider only the sling psychrometer. If
you buy an official US Weather Bureau sling psychrometer, it will contain the proper operating instructions and
tables for high accuracy usage. If the unit you obtain does not contain tables for various pressures, then you
should obtain the official pamphlet from the Superintendent of Documents at the US Government Printing Office.

The pamphlet’s name is “Psychrometric Tables for Obtaining the Vapor Pressure. Relative Humidity and
Temperature of Dewpoint from Readings of the Wet and Dry Bulb Thermometer, No. 235, Reprint 1941”: by
C.E. Marvin.

The calibration check is made by swinging the psychrometer as close as possible to the instrument under test.
You should swing the psychrometer at a rate of two revolutions per second for at least one minute. The readings
of the wet and dry bulbs should then be recorded and the procedure repeated until at least two consecutive
identical readings are obtained. You should then record the hygrometer’s reading, making sure the unit is in the
vertical position and lightly tapping the instrument. Also record the time of observation. Now following the
instructions supplied with the tables, determine the % RH and record it. Because of the relatively slow response
of most hygrometers compared to a psychrometer, you need to repeat the checking procedure every 15 to 30
minutes until the psychrometer and hygrometer readings are stable (usually within an hour).

Now that you have your comparative data, you must take into account the specified accuracy of both instruments.
As an example, we will use our COMFORTMINDER compared to an official weather bureau psychrometer. The
COMFORTMINDER has a rated accuracy of ±5% RH from 20 to 80% RH. The psychrometer is accurate to ±2%
RH from 0 to 100% RH. So, if the psychrometer reads between 20 and 80% RH, then the two instruments should
read within 7% RH of each other. If, however, the humidity is below 20% or above 80%RH, then no comparison
can be made because it is outside of the COMFORTMINDER’S accurate range. The seven percent span is
derived by adding the ± tolerances together, ±5% and ±2% = 7% (i.e. the COMFORTMINDER reads +5% and
the psychrometer reads –2%, then the difference is 7% RH). This shows us that if you were to compare two
COMFORTMINDERS they could read as much as 10% RH different and still be within calibration tolerances.

In conclusion, humidity measurement is one of the most difficult and least understood environmental
measurements made. We hope that this essay has helped you to understand humidity and its measurement.
However, this is far from a complete explanation, in fact, there is a branch of the sciences called Hygrometry that
deals with humidity measurement. If you want more detailed information, please refer to the publications listed
below:

Introduction to Meteorology Instruments for Physical Environmental
Author – Sverre Petterssen, PHD Measurements, Vol. I 2nd Edition
Publisher – McGraw Hill, Inc. Authors – J.Y. Wang and C.M.M. Felton
New York, NY Publisher – Kendall/Hunt Publishing
Library of Congress #68-15476 Dubuque, IA
Library of Congress #83-81613
A Field Guide to the Atmosphere ISBN #0-8403-3098-7
Authors – Vincent J. Schaefer and
John A. Day Humidity and Moisture, Vol. I to IV
Publisher – Houghton Mifflin Co. Publisher – Reinhold Publishing Corp.
Boston, MA New York, NY
Library of Congress #80-25473 Library of Congress #65-13613
ISBN #0-395-33033-5

Climate and Weather

Author – Hermann Flohn
Publisher – McGraw Hill, Inc.
New York, NY
Library of Congress #67-22978

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IMPORTANT ADDITIONAL INFORMATION

Components: Along with the indicator, the following components are included with this instrument:

Brass Case: Your brass case is solid brass A70-30 Holloware quality, with a durable lacquer

finish. It is in fact a piece of jewelry and should be treated as such. It should be cleaned at least
once a week to keep airborne pollutants (dust, etc…) and any moisture from collecting on the case
thereby attacking the lacquer. At no time should you use an abrasive cleaner or cloth on the brass
case. Simply use a soft cloth or soft paper towel with a mild glass cleaner to wipe the case clean.
If your instruments are in a summer home, and you are not able to clean them regularly, simply lay
a small cloth or towel across the top two-thirds so that dust cannot settle on the finish.

Specifications: All instrumentation or measuring devices have accuracy tolerances and

specifications. Making comparisons between different pieces of equipment is appropriate provided
the specified accuracies of both are known.

Measurement Range Guaranteed Accuracy

Temperature 10 - 110°F ±2°F
Relative Humidity 10 – 100% RH ±5% RH (20-80% RH)

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PROTEUS

SETTING AND OPERATION

INTRODUCTION

Inside the brass barometer case is a sealed, flexible metallic drum. As the atmospheric pressures changes,
the drum is compressed or expanded. This change is transmitted through linkage to a pointer - thus, change
in atmospheric pressure is evidenced by movement of the pointer around the dial. The linkage has a
bimetallic element which automatically compensates for changes in temperature which would otherwise introduce
an error in barometer readings.

SETTING YOUR BAROMETER

Your barometer has been carefully calibrated and tested at the factory and
needs but one simple adjustment before installation at your location. This
adjustment is made by inserting a screw driver in the recessed slotted screw
at the back of the barometer and turning this screw to the proper setting.

The simplest method of obtaining the correct barometric pressure for your
location is to consult the local weather bureau, airport or perhaps a nearby
individual with a correctly set barometer.

Due to the nature of aneroid (mechanical) barometers it may be necessary
to fine tune the initial setting to accomodate the natural mechanical break-in
of the device by simply repeating the setting procedure.

SCREW

WOOD
PANEL

SCREW

SCREW

We recommend mounting the read-out on
one of our pre-drilled and centered panels.

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PROTEUS

HELPFUL COMMENTS

Your barometer is a useful instrument for weather prediction. The settable
pointer, controlled by the knob in the center of the glass lens, is used to show
changes in atmospheric pressure. When reading your barometer, lightly tap
the case to take up normal slack in the linkage. Next, move the settable
pointer until it rests exactly over the movement pointer. The next time you
observe your barometer lightly tap the case again and you will now have
a clear indication of rising, falling or steady barometric pressure. Observation
of changes in barometric pressure, wind and temperature conditions give the
weather watcher a strong basis for forcasting the weather.

WITH A RISING BAROMETER THE FOLLOWING READINGS INDICATE:

28.8 TO 29.2 INCHES

29.2 TO 29.6 INCHES

29.6 TO 29.9 INCHES

29.9 TO 30.2 INCHES

30.2 TO 30.5 INCHES

30.5 TO 30.8 INCHES

30.8 TO 31.0 INCHES

CLEARING, HIGH WINDS AND COOL WAVE
HIGH WINDS, COOL WAVE, PRECEDED BY SQUALLS
FAIR WEATHER, FRESH WINDS DURING NEXT 24 HOURS
FAIR WEATHER AND BRISK WINDS, DIMINISHING
FAIR WEATHER, COOLER VARIABLE WINDS
CONTINUED COOL, CLEAR WEATHER, LIGHT WINDS
HIGH WINDS, SOUTHEAST WITH RAIN

WITH A FALLING BAROMETER THE FOLLOWING READINGS INDICATE:

30.8 TO 30.5 INCHES

30.5 TO 30.2 INCHES

30.2 TO 29.9 INCHES

29.9 TO 29.6 INCHES

29.6 TO 29.3 INCHES

29.3 TO 29.0 INCHES

29.0 TO 28.7 INCHES

Excerpt from "Eldridge Tide & Pilot Book"

FAIR, WEATHER, FOLLOWED BY RAIN
APPROACHING STORM.
CLOUDY, WARMER, UNSETTLED WEATHER.
UNSETTLED WEATHER, WARMER WITH INCREASING WIND.
SQUALLY, CLEARING, FAIR AND COOLER WEATHER.
CLEARING, HIGH WINDS WITH SQUALLS AND COOLER WEATHER.
STORMY WEATHER

NOTE: IF THE BAROMETER IS TO BE USED ABOVE 3000 FOOT ELEVATIONS,

THEN THE UNIT MUST BE COURSE ADJUSTED AT THE FACTORY TO THE

PROPER AL TITUDE.

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IMPORTANT ADDITIONAL INFORMATION

Components: Along with the indicator, the following components are included with this instrument:

Brass Case: Your brass case is solid brass A70-30 Holloware quality, with a durable lacquer

finish. It is in fact a piece of jewelry and should be treated as such. It should be cleaned at least
once a week to keep airborne pollutants (dust, etc…) and any moisture from collecting on the case
thereby attacking the lacquer. At no time should you use an abrasive cleaner or cloth on the brass
case. Simply use a soft cloth or soft paper towel with a mild glass cleaner to wipe the case clean.
If your instruments are in a summer home, and you are not able to clean them regularly, simply lay
a small cloth or towel across the top two-thirds so that dust cannot settle on the finish.

Specifications: All instrumentation or measuring devices have accuracy tolerances and

specifications. Making comparisons between different pieces of equipment is appropriate provided
the specified accuracies of both are known.

Measurement Range Guaranteed Accuracy

Barometric Pressure 27.5 – 31.5 Inches of Hg ±0.08 Inches of Hg

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MERIDIAN

INSTALLATION & OPERATION

INSTRUCTIONS

INSTALLATION

Please follow this procedure before setting your clock; if using any of our wall panels, squares
or free standing mantle mounts, simply screw into the existing holes the two supplied right angle
hangers. These hangers should be screwed in so that there is approximately a 1/2” space left
from the panel surface to the top surface of the hanger. On the back of your tide clock you will
find two (2) holes that will line up with the mounted right angle hangers.

Align the holes and the hangers and push the clock against the wall. The clock will now be up
against the three rubber feet on the back plate and not the rim of the brass case. While still
applying pressure against the rubber feet, simply move the clock down so that it seats on the
two (2) right angle hangers. If this fit feels too tight, back the hangers off one turn – if too loose,
screw the hangers in one turn.

If you are not using one of our panels, use the supplied template to spot the hanger holes on
your mounting surface. Using a #50 drill or a 1/16 drill, bore the two hanger holes. Now follow
the above instructions for clock mounting.

Note: There is, by design, a small gap between the clock case flange and the mounting
surface. Do not mount the clock via the three screw holes located around the outer rim
at the back of the clock case. Compressing of the back-plate of the clock may cause
improper operation and/or permanent damage.

IMPORTANT ADDITIONAL INFORMATION

Your brass case is solid brass A70-30 Hollowware quality with a durable lacquer finish. It is in
fact a piece of jewelry and should be treated as such. It should be cleaned at least once a week
to keep airborne pollutants (dust, etc…) and any moisture from collecting on the case thereby
attacking the lacquer. At no time should you use an abrasive cleaner or cloth on the brass
case. Simply use a soft cloth or soft paper towel with a mild glass cleaner to wipe the case
clean. If your instruments are in a summer home, and you are not able to clean them regularly,
simply lay a small cloth or towel across the top two-thirds so that dust cannot settle on the finish.

COMPONENTS

Along with the indicator, the following components are included with the instrument:

INC.

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PIN OR TACK

OR

TO MAKE LINE LEVEL

SPOT TWO HANGER HOLES

TO USE TEMPLATE USE A LEVEL

USE A PIN OR TACK TO MOUNT

LET THE TEMPLATE LEVEL ITSELF.

TEMPLATE ON WALL AT POINT SHOWN.

ATTACH A PAPER CLIP WHERE INDICATED.

HANGER HOOK LOCATIONS

4-7/16"

ATTACH PAPER CLIP HERE

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