SATO KEIRYOKI SK-181GT User manual

INSTRUCTION MANUAL
No. 8313-50 Heat Stress Monitor
Model SK-181GT
R.12

Introduction
Thank you for purchasing the Heat Stress Monitor Model SK-181GT.
This product is for measuring temperature, globe temperature, humidity and WBGT Index*. Do not use it for
other purposes.
*The heat index (WBGT) is an abbreviation for Wet Bulb Globe temperature, and is an index used to
evaluate the heat stress (thermal environment) of workers defined in “ISO7243 / JIS Z8504”. Please use
as a guide to prevent the heat stress.
Read this manual thoroughly before using the instrument and keep it in a safe place for your future reference.
PRECAUTION
Make sure you fully understand the following facts about this instrument before use for proper usage.
This instrument does not prevent a heat stress.
This instrument indicates WBGT index which can be used as guidelines for general heat stress.
Heat stress is caused not only by high temperature ambient, but also by one’s health condition, one’s
adaptability to hot environment, etc.
WARNING
Never use this instrument in an atmosphere exposed to inflammable gases as it may
explode.
* If there is anything you are not clear about this instrument, please contact us or the
dealer from which the unit was purchased.
CAUTION
Please keep to the following cautions for proper use of the instrument.
Use this instrument in a normal atmosphere only.
This instrument is not waterproof. Never let the instrument to get wet.
If the instrument gets condensed with moisture, turn the power off immediately and let it dry naturally
before using it again.
This is a precision instrument. Be careful not to drop or give shocks to it.
When storing or transporting the instrument, use the tray supplied. Do not use foam cushioning materials
(air packing, etc.), polyethylene bags (poly bags, etc.) or non-charged polyethylene bags (generally
colored bags such as light blue). Otherwise, the temperature and humidity sensors will be deteriorated
Never disassemble or alter the instrument to avoid any malfunctions and damages.
Never directly touch the temperature and humidity sensors.

Do not use the instrument in dusty environment. Otherwise, the coat of temperature and humidity
sensors will deteriorate.
If the instrument is used in an electrically noisy environment, the instrument could show unstable values
and errors in accuracy.
Using the instrument out of its measuring range can cause malfunctions and damages to both the main
unit and sensors. Use within the measuring range.
Do not leave the instrument in a car, etc. It may become extremely hot in the car in summer and it causes
the instrument to malfunction.
Do not wash or wipe this instrument with alcohol, thinner, or any other solvents. If the instrument gets
dirty, wipe it with a tightly wrung towel that has been dipped in warm detergent water.
If the instrument is not in use for a long period of time, always remove the battery. Otherwise, the battery
power may be wasted and the battery fluid may leak, resulting malfunctions.
Be careful when using the strap. It may cause an unexpected accident such as accidental suffocation
around the neck.
Do not swing the instrument with the neck strap, key ring, or carabiner attached. There is a risk of
unexpected accidents or damage.
* For repairs or calibrations, contact us or the shop that you purchased.
Overview
The SK-181GT is a handy type heat stress monitor which can measure globe temperature, air temperature
and relative humidity.
Compact body, but it has a globe and enables highly reliable measurement.
Features
JIS B7922:2023 class 2 compliant
Compliant with JIS B7922:2023 class 2 (electronic Wet Bulb Globe Temperature (WBGT) index meter). It
can be used as a guideline for preventing heat stress in sports activities, daily life, and labor.
Globe is equipped
The radiation heat (globe temperature) from direct sunlight can be measured.
Potable design
Compact size to be portable
Supports two types of heat stress prevention guidelines
Display is switchable between the “Heat stress prevention guidelines for exercise (* 1)” and the “Heat
stress prevention guidelines for daily life (* 2)”.
(*1) The “Heat stress prevention guidelines for exercise” compiled by the Japan Sport Association

(*2) The “Heat stress prevention guidelines for daily life” complied by Japanese Society of
biometeorology
WBGT measurement environment settings
The formula for calculating the heat index (WBGT) differs between outdoor measurements and indoor
measurements. The instrument can switch between outdoor and indoor measurements.
Alarm function
If the measured value reaches the set limit value of the heat stress index, a buzzer sounds and the
LED lamp flashes to alert.
Screw hole for a tripod is equipped
Useful to mount the tripod at measurement
Accessories
Carabiner, belt attachment parts, and neck strap are attached.
Cautions before Use
Check that the unit was not damaged during transport. Also, check if any accessories are missing before use.
If any damage or missing items are found, contact us or the dealer from where you bought the unit.

Names of Components
Front view Rear view
①
Globe
Inside the globe, there is a sensor to measure the radiation heat.
②
Sensing Section
Temperature and humidity sensors are inside of this section
③
LED lamp
The LED lamp blinks to alert
④
POWER key
On/Off key
Press this key to turn the main unit on. Press it again to turn off.
⑤
MENU key
Press this key to enter the setting mode.
⑥
SELECT key
In measuring mode, press this key to switch WBGT setting between outdoor
and indoor.
In setting mode, press this key to change the setting value.
⑦
Hook for key ring
Install the key ring through this hook
⑧
Buzzer speaker
⑨
Scerw hole for Tripod
⑩
Battery compartment
Battery compartment and cover with screw.

LCD Display
①
Heat stress index
Left:Display 5 stages of the “Heat stress prevention guidelines for exercise”
in 10 levels.
Right: Display 4 stages of the “Heat stress prevention guidelines for daily life” in
8 levels.
②
Indoor Mark
Indication for indoor values in WBGT mode
③
Buzzer Mark
Indication of buzzer setting
④
Keylock Mark
Indication of keylock.
⑤
Low Battery Mark
Indication of low battery. Replace immediately when it is displayed.
How to use
Loading and Replacing Battery
Before using the instrument for the first time, install a new battery.
When low battery mark appears on the display, replace the battery to new one.
①Use a “+” screwdriver to loosen the screw counterclockwise on the battery compartment.
NOTE: The screw is attached to the battery cover so that the screw cannot be
removed from the battery cover. If the screw is forcibly removed, the battery
cover will be damaged.
②Remove the old battery if replacing the battery.
③Set a new lithium coin battery (CR2032) with correct polarity that “+” is facing up.
④Close the battery cover and secure it with the screw.

CAUTION
Once the “Low Battery Mark” starts to light, replace with new batteries immediately.
Even if the unused battery if it has been stored very long time may cause a malfunction (such as a
buzzer sounding without being displayed). If this happens, replace with a new battery.
Both batteries must be the same type, and use all new ones. Different types or mixing with old batteries
may cause rupture or leakage.
Do not dispose of the used battery in a fire. Doing so may cause an explosion which may lead to an
injury.
For the environment conservation, dispose the used batteries in compliance with local rules and
regulations.
Keep batteries out of reach of children. If swallowed, contact a medical assistance immediately.
How to Measure
①Turn on the power by pressing the POWER key for longer than 2 seconds. After all characters are lit in
the display section for one second with the buzzer sound and LED lamp flashes, enter the measuring
mode.
②Have the instrument fully adapt to measuring ambient before measurement.
The heat index (WBGT), temperature, humidity, and heat stress level are displayed
③Press the POWER key for longer than 2 seconds to turn off.
CAUTION
Abrupt change of ambient temperature can effect on the accuracy of the instrument. Have the instrument
fully adapt to measuring ambient before use.
When the wind speed of the measurement environment is other than 0.3 to 3.0 m/s, an error may occur
in the heat index (WBGT).
How to Install
①Installing on a tripod
Attach the tripod (Cat. No.8310-80 Model M45) to the tripod screw hole on the unit.
Installation position: 1.2 to 1.5m above the ground.
②Wearing the instrument
Use the attached accessories (carabiner, belt attachment parts, and neck strap) to wear the instrument.
CAUTION
Install so that the globe is on top.

Do not block the vent of the temperature / humidity detector.
When wearing the instrument, do not cover the instrument with clothing.
When measuring in a sunny place, make sure that the entire globe is exposed to direct sunlight. Do not
let obstacles or clothing block the direct sunlight.
Switching WBGT measurement environment
The formula for calculating the heat index (WBGT) differs between outdoor and indoor measurement
environments. Switch the instrument's outdoor / indoor settings according to the measurement environment.
* The factory default setting is “Outdoor”.
How to set the WBGT measurement environment
Press the SELECT key in the measurement mode to choose the WBGT measurement environment setting.
Measurement environment
Environment Mark
Usage
Outdoor
mark is not displayed
When used outdoor (place in the sun)
Indoor
mark is displayed
When used indoor or outdoor at the place
not in the sun
Keylock function
To prevent the incorrect operation, the keylock function is equipped.
. How to activate the keylock function
①Press the MENU and SELECT key simultaneously in the measurement mode for longer than 2 seconds.
The keylock mark lights up and the key is locked.
②To cancel the keylock function, repeat ①. The keylock mark turns off and the keylock function is
canceled.
Various functions settings
How to set the “Heat stress index” and alarm
①Turn on the power. Press the MENU and SELECT key simultaneously for longer than 2 seconds to enter
the setting mode.
②Press the MENU key to switch the setting mode as shown below.

Heat stress index setting Alarm setting Buzzer setting
Display of Heat stress index
This instrument use bar graph to display the “Heat stress index” based on the “Heat stress prevention
guidelines for exercise” or based on the “Heat stress prevention guidelines for daily life”, which are derived
from the measured heat index (WBGT). The “Heat stress index” of measurement environment can be easily
checked.
* The factory setting is set as the “Heat stress prevention guidelines for exercise”.
①The “Heat stress prevention guidelines for exercise”.
5 steps (”Almost safe”, “Caution”, “Warning”, “Severe warning”, “Danger”) are displayed in bar graph
of 10 levels.
②The “Heat stress prevention guidelines for daily life”.
4 steps (“Caution”, “Warning”, “Severe warning”, “Danger”) are displayed in bar graph of 8 levels.

Please refer to the “Reference data” section for more information regarding each guideline for heat stress
prevention.
How to set “Heat stress index”
①Press the MENU key in the setting mode to enter the “heat stress index” setting.
②Press the SELECT key to choose the guideline of heat stress index.
“Heat stress index” setting
Usage
Heat stress prevention guidelines for exercise
Guidelines for preventing heat stress in sports activities.
Heat stress prevention guidelines for daily life
Guideline for preventing heat stress in daily life.
③Press the MENU key to continue to the alarm setting.
To return to the measurement mode, press the MENU key for longer than 2 seconds.
Alarm Function
The alarm is triggered with sound of buzzer and blinking LED light when the “Heat stress index” exceeds the
set value.
* The factory setting is “Severe Warning” in the “Heat stress prevention guidelines for exercise” with buzzer
ON.
•Alarm action
・If the measured value reached to set “Heat stress index”, an alarm is activated for 10 seconds.
・If measured value continues to exceed the set “Heat stress index”, the alarm will be activated for 2 seconds
every 10 minutes.
・If the “Heat stress index” is higher than set limit and if there is an increase or decrease in the “Heat stress
index”, an alarm will be activated for 10 seconds to notify the change.

The Buzzer sound: The different buzzers will be activated depending on the “Heat stress index”.
Heat stress prevention
guidelines for exercise
Heat stress prevention
guidelines for daily life
Buzzer sound
Almost safe / Caution
Caution
Beep, Beep, Beep
Warning
Warning
Beep-Beep, Beep-Beep,
Severe warning
Severe warning
Beep-Beep-Beep, Beep-Beep-Beep
Danger
Danger
Beeep, Beeep (long beep)
The LED lamp flashes: The LED lamp flashes while the alarm is sounding.
* If the alarm sounds, take the appropriate actions to prevent the heat stress.
Please refer to the “Reference data” for the actions of the heat stress prevention guidelines.
•How to set alarm function
①Press the MENU key in the setting mode to enter the Alarm Setting.
②Press the SELECT key to choose the “Heat stress index”. The bar lights up to the Heat stress index to be
set.
The “Heat stress prevention guidelines for exercise”
The “Heat stress prevention guidelines for daily life”
*The Alarm Setting cannot be canceled.
③To continue to the buzzer setting, press the MENU key.
To return to the measurement mode, press the MENU key for longer than 2 seconds.

⚫How to set Buzzer function
①Press the SELECT key in the buzzer setting to set buzzer ON/OFF.
Buzzer Mark
Description
is displayed
Buzzer ON
is not displayed)
Buzzer OFF
*When the buzzer is OFF, the alarm action is only LED flashing.
LED flashing cannot be turned off.
②Press the MENU key for longer than 2 seconds to return to the measurement mode.
How to install the mounting accessories
The instrument can be worn with the mounting accessories. When attaching the mounting accessories, pass
the key ring through the ring hole of the unit as shown below.
・Neck strap
Used when hanging the instrument from the neck
・Carabiner
Used when hooking the instrument.
・Belt attachment parts
Used when fixing the instrument to the belt. Fasten the belt mounting parts to the belt as shown in the
figure below and attach the instrument.

CAUTION
Be cautious when using the neck strap. It may cause an unexpected accident such as accidental
suffocation around the neck.
Do not swing the instrument with the neck strap, key ring, or carabiner attached. There are the risks of
unexpected accidents or damages.
Reference Data
The followings are a reference material about the heat stress index (WBGT).
The Wet Bulb Globe Temperature (WBGT) is a composite temperature used to estimate the effect of
temperature, humidity, and solar radiation (globe temperature) on humans. It is used by industrial hygienist,
athletes, and the military to determine appropriate exposure levels to high temperatures. It is derived from the
following formulas.
Outdoors: WBGT= 0.7 x WB + 0.2 x TG + 0.1 x DB
Indoors: WBGT= 0.7 x WB + 0.3 x TG
WB = Wet bulb temperature
TG = Globe temperature
DB = Dry bulb temperature
The “Heat stress prevention guidelines for exercise” compiled by Japan Sports Association
WBGT
Wet bulb
temperature
Dry bulb
temperature
Warning
level
Guides to how much exercise can be safely
performed
Above 31°C
Above 27°C
Above 35°C
Danger
Except for special cases, all exercise should
be stopped. It should be discontinued
especially for children.
28 to 31°C
24 to 27°C
31 to 35°C
Severe
Warning
The risk of heat stress is high, so avoid
exercises that tend to increase body
temperature, such as intense exercise or
endurance running
25 to 28°C
21 to 24°C
28 to 31°C
Warning
The risk of heat stress increases, so take a
break and replenish water with salt as
appropriate. In intense exercise, have a rest
every 30 minutes.

21 to 25°C
18 to 21°C
24 to 28°C
Caution
There is a possibility of fatal accidents due to
heat stress. Pay attention to signs of heat
stress, and actively drink plenty of fluid and
take salt to keep sodium balance between
exercises.
Below 21°C
Below 18°C
Below 24°C
Almost
safe
The risk of heat stress is usually low, but
supplementation with water and salt is
necessary. Heat stress could occur even
under these conditions in events such as
marathons, so caution is advised.
Reference: Japan Sports Association, "A Guidebook for the Prevention of Heat Disorder During Sports
Activities", 2013.
The “Heat stress prevention guidelines for daily life” complied by Japanese Society of
Biometeorology
WBGT Index
Risk of occurrence in relation to
physical activity
Remarks
Danger
(31°C or higher)
Risk during any physical activity
Risk of occurrence is high in the elderly,
even in the resting state. Avoid going out and
stay in a cool room
Severe warning
(28 to 31°C)
Avoid direct sunlight outdoors and watch for
any rise in room temperature indoors
Warning
(25 to 28°C)
Risk during moderate to vigorous
physical activity
Regularly take adequate rest when
exercising or doing vigorous work.
Caution
(25°C or lower)
Risk during very vigorous physical
activity
Basically, low in risk, but high in risk when
doing vigorous exercise or heavy labor

Errors Displays and Safety Instructions
If there is a malfunction detected, one of the following error codes will be displayed.
Type
Code
Description
Solution
WBGT
Temperature
Humidity
E02
The measured value is under the
display range.
Use within the measuring range.
If doing so still does not solve the
problem, there is a possibility that the
sensor could be malfunctioning.
E03
The measured value is over the
display range.
WBGT
E04
Unable to calculate the heat index
WBGT.
Use within the measuring range.
If doing so still does not solve the
problem, there is a possibility that the
sensor could be malfunctioning.
If an error message other than the above is displayed or If the above-mentioned solution doesn’t work,
please contact us or the dealer from which the unit was purchased for assistance.
Trouble shooting
Trouble
Possible Cause
Solution
The power cannot be
turned on.
The battery is exhausted.
Replace with new batteries.
The displayed value is
not stable.
The instrument does not adapt in
the ambient temperature
Let the instrument adapt to the ambient
before use.
The electric noises generated
from the environment may affect
Do not use the unit in the circumstances
where electric noises are generated. Doing
so may result in unstable display or large
errors.
Abnormal value is
displayed.
The electric noises generated
from the environment may affect
Do not use the unit in the circumstances
where electric noises are generated. Doing
so may result in unstable display or large
errors.
If the above-mentioned solution doesn’t work, please contact us or the dealer from which the unit was
purchased for assistance.

Specifications
Cat. No. : No. 8313-50
Model : SK-181GT
Measuring Range :Temperature : 0.0 to 50.0°C
Globe Temperature* : 0.0 to 60.0°C
WBGT : 0.0 to 50.0°C
Humidity : 10.0 to 95.0% rh
Accuracy :Temperature : ± 0.6°C (20.0 to 40.0°C)
: ± 1.0°C for others
Globe Temperature* : ± 0.6°C (20.0 to 40.0°C)
: ± 1.0°C for others
WBGT : ± 2.0°C (20.0 to 40.0°C)
: ± 3.0°C for others
Humidity : ± 5.0% rh (30% to 90% at 20 to 30°C)
± 7.0% rh for others
Resolution :0.1
Sampling Time : Approx. 20 seconds
Conformity Standards :Confirming to JIS B7922:2023 Class 2
Operation Ambient : 0 to 50°C, less than 95% rh (no condensing),
Wind speed 0.3 to 3.0 m/s
Storage Ambient : -10 to 50°C (no condensing)
Power Requirement : 3VDC (Lithium coin battery (CR2032) × 2 (in parallel connection))
Battery Life :Approx. 6 months in continuous use with alarm activated twice a day
Materials (case, globe) : ABS resin
Dimensions : Body : (W) 60 × (H) 122 × (D) 25 mm
Globe : ø 40 mm
Weight : Approx. 70 g (including battery)
Standard Accessories : Instruction manual, Lithium coin battery (CR2032) × 2,
neck strap x 1, carabiner x1、belt attachment parts x1, key ring x1
*Globe temperature is not displayed.
**All specifications and appearance are subject to change without notice for improvement purpose.
Optional Accessories
No. 8310-90 Tripod for SK-181GT Model ZF-400WSH
For details, contact us or a retailer from which you have purchased.
SATO KEIRYOKI MFG. CO., LTD.
3-4, Kanda-kajicho, Chiyoda-ku, Tokyo 101-0045, Japan
https://www.sksato.co.jp/
As of Jun. 2023