what is the WGBT?
- a measure of heat stress
WGBT considers the effects of
- air temperature, humidity, wind speed, and radiant heat (indoor measurements), 0.7 WB + 0.3TG
- air temperature, direct (solar) or radiant sunlight, wind speed and humidity (outdoor measurements), 0.7 WB + 0.2 TG _ 0.1 TA
ACGIH publishes TLVs
- american conference of governmental industrial hygienists publishes threshold limit values that have been adopted by many governments for use in the workplace
- the process for determining the WBGT is also described in ISO 7243, hot environments - estim
WGBT features
- in/out function displays the WBGT value w/or w/out direct sun exposure
- view temperatures in either F or C
- meter can switch to manual data logging
- SD card capacity: 1 GB to 16 GB
- data hold, record max and min reading
WGBT parts (1/2)
- black ball (TG sensor)
- black ball fix screw
- humidity and air temperature (TA) sensor
- display
- function, hold & next button
- REC, enter & in/out button
- logger, up & sampling time check button
- power, ESC & backlight button
- SET, down & time c
WGBT parts (2/2)
- battery screw covers
- tripod fix nut
- battery compartment/ cover
- stand
- USB/RS232 output
- reset button
- AC/DC 9V power adapter input socket
power on/ off
- turn on the meter by pressing the power button
- to turn the meter off, hold the power button for over 2 seconds
function selection: the meter has 5 measuring functions to choose from
1) WGBT: wet bulb globe temp
2) WB: wet bulb temp
3) TG: black globe temp
4) dP - dew point
5) tA & rH - air temperature & humidity
black globe temperature (TG)
- measured using a black globe temperature sensor
- includes a black globe w/ a thermometer inserted in the center
- monitors the effects of direct heat or solar radiation on its exposed surface
wet-bulb temperature (WBT)
- the temperature read by a thermometer covered in a (typically) water soaked cloth (wet-bulb thermometer) over which air is passed
- at 100% relative humidity, the wet-bulb temperature is equal to the air temperature (dry-bulb temperature)
- the WB is lo
dew point (dP)
- the temperature at which air is saturated w/ water vapour
- when air has reached the dew-point temperature at a particular pressure, the water vapour in the air is in equilibrium w/ liquid water, meaning water vapor is condensing at the same rate at whi
relative humidity (rH)
- the ratio of the pressure of water vapour in a parcel of air relative to the saturation pressure of water vapour in that same parcel of air at a specific temperature
- expressed as a percentage
- the relative humidity is 100% when the dew point and temp
dP and rH
- compared to relative humidity, dew point is frequently cited as a more accurate way of measuring the humidity and comfort of the air since it is an absolute measurement (unlike relative humidity)
- most people are comfortable w/ a dew point temperature
air temperature (TA)
- measured using a thermometer
- thermometer: a device that measures temperature or a temperature gradient
WBGT measurement
- press and hold "function, hold & next button" to switch between function selections
- choose the function "_bgt". the upper display will show the WBGT value. the lower display will toggle between the text "_bgt" and "in" for indoors or "bgt" and "out" f
wet bulb measurement
- function select to "_b"
- the upper display will show the WB value
- the lower display will show the text "_b
dew point measurement
- function select to "dP"
- the upper display will show the dew point temperature value
- the lower display will show the text "dP
humidity and air temperature measurement
- function select to "rH"
- the upper display will show the humidity value
- the lower display will show the TA (air temperature) value
black globe measurement
- function select to "tg"
- the upper display will show the TG value
- the lower display will show the text "tg
data hold
- while taking a measurement, quickly press and release the "function/hold" button once and the measured value will hold on the screen, and a HOLD symbol will appear
- quickly press the hold button once again will release the data hold function
data logger: prep before executing the data logger function
1) insert the optional SD card into the SD card socket
2) before you use an SD card w/ this meter for the first time, it is recommended to format the SD card
3) if this is the first time the meter is used, using the advanced setting (see next slide) you w
advanced settings
- during normal functions, press and hold the SET button for 2 seconds to enter the "advanced setting" mode
press the NEXT button scroll through 8 main functions, shown on the lower display:
- dAtE set clock time (year/month/date, hour/minute/second)
- AL SET WBGT alarm value
- dEC set SD card Decimal character
- PoFF Auto power OFF management
- bEEP set beeper sound ON/OFF
- t-CF select the temperature unit to degC or F
- SP-t set sampling t
advanced settings - format SD card
- before you use an SD card w/ this meter for the first time, it is recommended to format the SD card in preparation for data logging (formatting erases all previous data from that SD card)
how to erase previous data from the SD card
- insert the optional SD card into the SD card socket
- press and hold the SET button for 2 seconds to enter the "advanced setting" mode
- press the NEXT button scroll through 8 main functions to show Sd F
- use the "up/down" arrows to select the "yES" to
advanced settings - set date/time
- during normal functions, press and hold the SET button for 2 seconds to enter the "advanced setting" mode
how to set date/time
- press the NEXT button to scroll through 8 main functions to show dATE
- press the "enter" button to display the year
- use the "up/down" arrows (set/logger buttons) to set the year
- press the "enter" button to display the month and use the up/down arro
advanced settings - set decimal point character
- during normal functions, press and hold the SET button for 2 seconds to enter the "advanced setting" mode
- press the NEXT button to scroll through 8 main functions to show dEC
- use the up/down arrows (set/logger buttons) to toggle between "bASIc" (".
data record
- the data record function records the maximum and minimum readings
- press the REC button once to start the Data Record function and a "REC" symbol will appear on the display.
with the "REC" symbol on the display: 1)
1) press the REC button once, and a "REC MAX" symbol along w/ the maximum value will appear on the display.
- to delete the maximum value, press the Hold Button once and the display will show a "REC" symbol only and execute the memory function continuousl
with the "REC" symbol on the display: 2)
- press the REC button again and a "REC MIN" symbol along with the minimum value will appear on the display
- to delete the minimum value, press the Hold Button once and the display will show a "REC" symbol only and execute the memory function continuousl
with the "REC" symbol on the display: 3)
- to exit the memory record function, press the REC button for 2 seconds
- the display will revert to the current reading
auto data logger (sampling time set > 1 sec): 1)
1) set the sampling time to 1 second or more, use the advanced settings
auto data logger (sampling time set > 1 sec): 2)
2) start datalogging; press the REC Button and the "REC" symbol will appear on the LCD screen, then press the Logger Button, the "REC" symbol will flash while the measuring data and time information is being saved in memory
auto data logger (sampling time set > 1 sec): 3)
3) to stop datalogging, press the REC button for 2 seconds
- the "REC" symbol will disappear indicating the Datalogging function has stopped
auto data logger (sampling time set > 1 sec): 4)
4) to pause the datalogging, press the Logger button once
- while paused, the REC symbol will stop flashing
- press the Logger button again to resume datalogging, and the REC symbol will begin to flash again
Manual data logger (sampling time set = 0 sec): 1)
- set the sampling time to 0 seconds
Manual data logger (sampling time set = 0 sec): 2)
- press the REC button and the REC symbol will appear on the LCD screen
Manual data logger (sampling time set = 0 sec): 3)
- press the logger button, and the REC symbol will flash once and one Beep will sound (if set), at the same time the measuring data, along the the time information, will be saved in memory
- the lower display will show the position (record) number, which
Manual data logger (sampling time set = 0 sec): 4)
- to change the position number, press the Down button and the lower position number will flash on the display
- press the up or down buttons to set the position number (1 to 99) to help identify the measurement location
- the lower display will show P x
Manual data logger (sampling time set = 0 sec): 5)
- to stop datalogging, press the REC button for 2 seconds, and the REC symbol will disappear indicating the Datalogging function has stopped
SD card data structure: 1)
- the first time the SD card is used in the meter, the SD card will generate a folder: WBA01
SD card data structure: 2)
- the first time you use the Datalogger, in the folder WBA01, a new file name WBA01001 XLS will be created
- the datalogger will use this file until the Data has reached to 30 000 rows
- the meter will then generate a new file w/ a subsequent number, for
SD card data structure: 3)
- the folder WBA01 can hold 99 XLS files
- when that number has been reached, the meter then will generate a new folder w/ a subsequent number for example WBA02
- max number of WBA -- folders is 10
data transfer from SD card to computer (excel software): 1)
- after datalogging, remove the SD card from the SD card slot
data transfer from SD card to computer (excel software): 2)
- w/ your computer on, plug in the SD card (ensure it is unlocked into the computer's SD card slot or insert the SD card into the optional SD card adapter and connect to your computer
- a folder will appear on your desktop representing your SD card
data transfer from SD card to computer (excel software): 3)
- open the files w/ EXCEL (File - Open), if they don't automatically
data transfer from SD card to computer (excel software): 4)
- the EXCEL file will have the following column headers in this order: Place (position number), data (year/month)day), time (in 24h clock), value and unit
energy expenditure prediction program (EEPP)
- developed by the university of Michigan
- a software tool to estimate energy expenditure rates (workloads) for materials handling tasks to help assure worker safety and health
EEPP
- based on the assumption that a job can be divided into simple tasks (activity elements) and that the average metabolic energy rate of the job can be predicted by knowing the energy expenditure of the simple tasks ad the time duration of the task
useful in:
- designing new jobs
- comparing one job to another
- improving an existing job by identifying the particular tasks that require excess energy expenditure
EEPP software provides...
- an objective rate to gauge fatigue which can also be compared with NIOSH guidelines
EEPP: step 1 - determine task work elements
- observe job, determine cycle time, list all tasks that occur w/in the cycle
- describe tasks as walk, carry, lift, lower, climb, push, pull, armwork, handwork and holds
- note start and finish heights of lifting, distances walked or carried, heights cli
EEPP: step 2 - enter data into EEPP
- during of standing, standing bent, sitting
- task information & description, duration and cycle duration
- subject's gender and weight
- task elements that include frequency, weight of load, force to push or pull, distance carried
- do not use symbols,
EEPP: step 3,4,5
3) perform the analysis of output - kcal/min
4) compare the output against guidelines for energy expenditure (3.5 kcal/min action limit for an average 8 hour day, 5.0 kcal/min maximum permissible limit for an average 8 hour day, if administrative controls
thermal comfort zone: summertime workplaces
- for summertime workplaces, where clothing is minimal, the environmental conditions should fall within the following ranges:
- air temp between 23 and 27 degC (73 and 80 degF)
- at a lower limit of humidity, dew point should be greater than 2 degC or the
thermal comfort zone: wintertime workplaces
- where clothing is thicker and/or layered, the environment conditions should fall within the following ranges:
- air temperature between 20 and 24 degC (68 and 75 degF)
- at a lower limit of humidity, dew point should be greater than 2 degC or equivalent
are there any standards on office temperatures?
- the CSA standard CAN/CSA Z412-00 (R2011) - "office ergonomics" gives acceptable ranges of temperature and relative humidity for offices in Canada
- these values are the same as recommended by ASHRAE standard 55 - 2010 "Thermal Environmental Conditions f
are there any general guidelines about maximum temperature conditions in offices?
- when the humidex rating is in the 40-45 degC range, most people would find it uncomfortable
- however many kinds of work must be restricted when the humidex is above 45 degC
only one jurisdiction that we know of has...
- a directive about the temperature and humidity conditions when employees should be relocated or release from the office workplace
- this reference is the national joint council in part II - permanent structures and safe occupancy of the workplace (use a
what does it state?
- that if the humidex reading exceeds 40 degC [measured inside the building - not based on weather reports or outdoor air temperatures] it is considered to be an unsatisfactory condition
"in those cases, operations shall be stopped and employees released
what is the wind-chill temperature?
- at any temperature, you will feel colder as the wind speed increases
- the combined effect of cold air and wind speed is expressed as "equivalent chill temperature" (ECT) or simply "wind chill" temperature in degrees C or F
- it is essentially the air t
in some parts of canada...
- the term "wind chill factor is used
- its a measurement of the heat loss rate caused by exposure to wind and its expressed as the rate of energy loss per unit area of exposed skin per second (ex. joules/[second-metre^2] or watts/metre^2, W/m^2)