SATO KEIRYOKI SK-RHG User manual

No. 7450-00 Assmann Type Psychrometer
Model SK-RHG
Instruction Manual

1
Thank you for purchasing Assmann type psychrometer Model SK-RHG.
Read this manual thoroughly before using the SK-RHG. Keep the manual in a safe place for future
references whenever necessary.
1. Descriptions
The SK-RHG is an aspirated psychrometer that it is said as the most stable measuring method for
relative humidity.
Two glass thermometers are equipped in the body. The one whose bulb is covered with a wick is
called as wet-bulb thermometer and another one is called dry-bulb thermometer. The temperatures
that wet bulb and a dry bulb thermometer measure are different. Based on this difference between
them, The Assmann psychrometer detects relative humidity (RH) using Sprung’s formula to convert
the temperature into a humidity reading.
You can use the Assmann psychrometer in any application where accurate relative humidity
measurements are required, not only meteorological observation.

2
2. Names of Section
Hanging ring
Battery compartment cover
Screw cap
Screw cap
Battery
compartment
DC jack and
protective cap
Main housing Thermometer (dry bulb) Thermometer
(wet bulb)
Stand fastener
Reservoir holder
Water reservoir
Air intake tube
for dry bulb
Water reservoir
Left side view Front view
Right side view
Power switch
Air intake tube
for wet bulb
(upper part)
Air intake clamp
Air intake tube
for we bulb
(lower part)
Hanging ring
Screw cap
Air intake tube for wet
bulb (upper part)
Air intake tube for
wet bulb (upper part)
Power switch
Stand fastener
Reservoir holder
Water reservoir
Main housing
Air intake clamp

3
3. How to use
3-1 Preparation (Unpacking procedure)
1) Open the carrying case
2) Check the appearance for the damages or scratches on the main unit and thermometers.
3) Check that you have all accessories referring to the manual
* If you find any damage or shortage, contact the dealer or our service network.
3-2 Installation of the main unit
Mount the unit by using either the optional compact
stand or the hanging ring on the top.
NB. Do not hold the unit in your hands while measuring.
Doing so may result in inaccurate measurement.
A tripod for hanging the unit is provided at option.
3-3 Operation procedure
1) Pressing the power switch to Black (OFF) to turn the power off.
(Black: OFF, Orange: ON)
2) Loading batteries
Remove the lid of the battery compartment. While
confirming each polarity (+) or (-) shown in the battery
compartment, load 2 “D” sized batteries to the battery
compartment. Then reinstall the battery lid.
External power supply is also available.
Connect the supplied AC adapter to the DC jack on the
left side of the head.
Stand fastener
Optional stand
Hanging ring
Power switch
Battery compartment
cover
DC jack
AC adapter
Cap

4
3) Setting the string
Carefully pull the string from the guide and place the string into the
water reservoir.
NB. Thoroughly wash your hands or use forceps avoiding to
adhering hand stains, salts and acids on the string or wick.
4) Pouring water
Fill the water reservoir to four-fifths with distilled water using the water bottle supplied.
NB. - Ordinary tap water should be avoided because it affects the accuracy of the measurements.
- Be sure that the inside of the air intake tube
stays dry. Moisture on the walls of the intake
tube will cause lower-than-normal wet bulb
temperature.
5) Start measurement
Place the power switch in ON position (switch turns to orange).
The ventilation fan will begin to turn.
NB: Warm up the unit for at least five minutes after it is turned on.
6) Measurement end
Turn off the unit by pressing the power switch (switch turns to black)
Cautions on measurement
When you read the temperature, your eyes are (at right angle) level to
the thermometer and the top of mercury or alcohol level.
Do not bring your face too close to thermometer since the heat of your
breath and body affects readings. Read temperature quickly so as not to
get too close to the thermometer.
Avoiding any possible reading error, read tens place first and then
smaller places.
Wick of the wet bulb will dry out quickly in high temperature/low humidity environment.
Make sure to refill water to the water reservoir.
It takes approx. 2 minutes in mercury-filled thermometer and approx. 5 minutes in alcohol-filled
thermometer for the indicated value to stabilize.
4. Maintenance
4-1 Replacing the wick
Maintaining the wet bulb
Before using the instrument, make sure the wick is free from dust and dirt. If it is dirty, replace
the wick.
NB: * Replace wick and distilled water and clean the water reservoir once every seven days.
* Be sure your hands are clean when replacing the wick.
Air intake clamp
Water reservoir
String
Fill water
four-fifths full
Water reservoir
Water
reservoir
Power
switch
Press to
change to
black (OFF)

5
How to replace the wick
1) Pull horizontally the air intake clamp to remove
and pull down the air intake tube.
2) Pull down the old wick and clean the bulb of
thermometer with clean, dry cloth.
3) Use forceps to attach a wick to the bulb of
thermometer
4) Don’t let the string get stuck or caught between
the housing and air intake tube, between the
clamp and air intake tube or in the grooves.
5) Join the upper and lower sections of the air
intake tube and lock with the clamp.
Carefully connect the clamp tabs with the
groove on the upper part of the air intake
tube
6) Reattach the water reservoir to the reservoir
holder, and place the string into the reservoir.
Air intake tube
(upper part)
Groove
for clamp
Air intake
tube
(lower part) Clamp tabs
String guide Hole for
string
Clamp
Air intake tube
(upper part)
Air intake tube
(lower part)
Old wic
k
Air intake clamp
Water reservoi
r
String
Air intake tube
(lower part)
String
Grooves
Air intake tube
(upper part)
Air intake tube
(upper part)
Install the wick by
aligning the string
with the groove
for strin
g
.
Groove for string
Wet bulb wic
k
Thermometer bulb

6
4-2 Using gauze as the wet bulb wick
Using gauze is an alternative to using the standard wicks when more accurate measurement is
required at the state of lower than 25%RH.
How to replace gauze
1) Remove the old wick as shown in “Replacing the wick”.
2) Use gauze and a thread made of cotton fiber.
We do not recommend a synthetic fiber. Boil the gauze and cotton
thread in soapy water, rinse the materials with distilled water to remove
soap residues and oils.
3) Cut a piece of gauze large enough to fit around the bulb (100 x 15 mm), and dampen it with distilled
water. Extend the gauze about 10mm from the end of the bulb, and wind the gauze around the
sensing part without making wrinkles.
4) Use cotton thread to tie the gauze firmly above the bulb
5) Tie of the end of the gauze with another piece of tread. The
knot should be snug.
6) Cut off the gauze about 2 or 3 mm beyond the end of the
bulb.
7) Carefully pull out and remove the horizontal threads (woofs)
of gauze above the hollow of the bulb, leaving only the
vertical strands (warps). Make a string by binding the
remaining wraps of gauze.
8) Follow steps (4) and (5) in “Replacing Wick”. Replace the lower part of air intake pipe, clamp,
water reservoir, and insert the string into the water reservoir.
Tie off the end of
the gauze
Cut off the gauze
Make a string by
binding the
remaining warps
Knot
above
bulb
Bulb
Use cotton thread
to the gauze firmly

7
4-3 Replacing thermometers
Note: The thermometer with a metal cap that is used with a traditional Assmann psychrometer is not
usable. Be sure to use the dedicated thermometers for SK-RHG.
1) Removing the glass thermometers
Turn the screw cap counterclockwise with a screwdriver or coin.
Push the thermometer up through the opening and get it out.
2) Installing the glass thermometers
Insert a new glass thermometer down into the
opening. Be sure the thermometer is all the way
down and positioned correctly.
Tighten the screw cap until it stops.
5. Accessories
5-1 Storage method
When not using for a long time, store the SK-RHG Assmann
psychrometer in the carrying as shown as the right figure.
At this time, remove the batteries, the wick (or gauze) and
water reservoir
5-2 Setting the strap
(1) Pass the strap through the loops of the carrying case.
Be sure to pass it through the bottom loop.
(2) Set the shoulder pad so that the skid-proof side will
touch your shoulder.
Insert the
thermometer
through opening
up to the screw
Tighten the
screw cap
until it stops
Loop Strap
Loop Loop
Screw cap
Thermometer
Strap
Shoulder pad
Skid-proof

8
6. Cautions
Do not throw or drop the SK-RHG since the main parts of SK-RHG is glass thermometers
The humidity conversion chart for Aspirated psychrometer is cleated by using Sprung’s formula.
Do not use the chart other than Aspirated psychrometers
When the wet becomes dirty, replace it immediately for accurate measurement
Do not store or use the SK-RHG in a place where the environmental
temperature exceeds the maximum temperature range of the
thermometer.
In such a high temperature state, thermometer may break.
Always place the SK-RHG so that the bulb of glass thermometer is
not higher than horizontal. If so, the thread of mercury or liquid
may break.
Motor life
A small brush motor is used in SK-RHG. Be sure to turn off the power switch except measurement
time. Unnecessary continued use accelerates brush attrition and shortens the life of the motor.
The motor life is approx. 200 hours.
* Brushless motor is available at option.
7. Specifications
Product
A
ssmann type psychrometer (AC/DC type)
Model S
K
-RHG
Cat. No. 7450-00 7450-20
Measuring Range 0 to 50.0°C 0 to 50.0°C
Thermometer Mercury-filled dual tubing
(Blue liquid) Alcohol-filled dual tubing (Red liquid)
Min. graduation 0.2°C 0.2°C
Measurement
Accuracy within ±0.2°C within ±0.2°C
Speed of airflow 3m/s to 5m/s
Power Requirements 3VDC (2 “D” manganese batteries) or AC adapter
Battery life approx. 20 hours (in continuous use at 3m/s or more
Outer Dimensions 80 (W) × 450(H) × 110 (D) mm
Weight approx. 0.74kg (excluding the batteries)
Standard Accessories Wicks (20 pcs.), Humidity conversion rule, water supply bottle, test result for
thermometers, dustproof cover, 2 “D” manganese batteries. carrying case

9
8. Changes of voltage of battery and speed of air flow continuous use
* To obtain accurate readings of humidity (%), operate in 3 to 5m/s of air flow and more than 2.2V load voltage.
* This product is available to continuously use for 20 hours and when it is used 4 or 5 times per day with 15 min.
interval, it is used for approx. two months
9. Consumables and optional accessories
* Thermometers (2 pcs./set with test result, length: 300mm)
No. 7450-50 Mercury-filled thermometer (Range: 0 to 50°C, div. 0.2°C)
No. 7450-60 Mercury-filled thermometer (Range: -30 to 50°C, div. 0.2°C)
No. 7450-67 Alcohol-filled thermometer (Range: 0 to 50°C, div. 0.2°C)
No. 7450-68 Alcohol-filled thermometer (Range: -30 to 50°C, div. 0.5°C)
* Others
No. 7450-30 Compact stand for SK-RHG exclusive use
No. 7450-40 Tripod
No. 7450-70 Wick for SK-RHG exclusive use (60 pcs. /box)
No. 7450-75 AC adapter in 100 to 240 VAC use
air flow
air flow
load voltage
load voltage
hours
2 “D” manganese batteries

10
10. How to determine humidity
10-1 Use of humidity conversion rule
Example: Dry bulb temperature (t): 25°C
Wet bulb temperature (t’): 18°C
10-2 Use of humidity conversion chart
Example: Dry bulb temperature (t): 29°C
Wet bulb temperature (t’): 27°C
1) The temperature difference (t°) between wet bulb (t’) and the dry bulb (t) is 2°C
t – t’= t° (27°C – 29°C = 2°C)
2) Refer to the humidity conversion chart
. Read t° cross the top of the chart to “2.0”which is the temperature difference.
. Read t’ down the side of the chart to “29” which is the dry bulb temperature.
. The intersection of the column“2.0” and the row“29” shows “86”, which means
R.humidityis86%.
The
▲ points 50, which means R. humidity is 50%
Temperature difference between the dry bulb (t) and the Wet bulb (t’)

11
Chart 1 If wet bulb is ice-free at 1013 hPa
Psychrometer formula : Sprung’ formula
Psychrometer coefficient : 0.000 662K1
Saturated vapor pressure against water : Sonntag’s formula
Dry bulb Temperature (°C)
Temperature difference between the dry bulb (t) and the Wet bulb (t’)

12
Chart 2 If wet bulb is ice at 1013 hPa
Psychrometer formula : Sprung’ formula
Psychrometer coefficient : 0.000 583K3
Saturated vapor pressure against water : Sonntag’s formula
Temperature difference between the dry bulb (t) and the Wet bulb (t’)
Dry bulb Temperature (°C)

Q07
3-4, Kanda-kajicho, Chiyoda-ku, Tokyo 101-0045 Japan
URL: http://www.sksato.co.jp/english