OVERVIEW
The Microtherm WBGT from Casella Cel is an ergonomically designed,
compact, and rugged instrument designed to monitor heat stress potential
of personnel in hot working environments in accordance with ISO 7243
It is the first heat stress meter that offers real-time graphical
display of data and also features an audible/visual alarm which allows
the operator to make raid decisions if required. PC software for
retrospective data analysis is included.
WHAT
IS HEAT STRESS?
Workers exposed to hot working environments can be susceptible to
heat stress, when the core body temperature rises to dangerous or
hazardous levels. This can result in physiological symptoms like heat
cramps, nausea, palpitations, stroke and possibly death.
An overall estimation of heat stress levels on the body can be
measured by utilising the Wet Bulb Globe Temperature Index (WBGT). This
combines the measurement of three parameters; natural wet bulb
temperature (tnw), globe temperature (tg) and air temperature (ta),
applied to the following formula for both indoor and outdoor
environments:
WBGT (Indoor)= 0.7tnw+ 0.3tg
WBGT (outdoor)= 0.7tnw+ 0.2tg+ 0.l ta.
The data collected for these values are compared to reference values
as defined by the standard and appropriate "work rest" regimes
can then be adopted in the work place or more detailed medical analysis
undertaken.
FEATURES
| Large LCD graphics display |
| Real time display |
| Full data-logging facilities as standard |
| Audible / visual alarm for WBGT levels |
| RH% and dewpoint calculation |
| Automatic calculation of work rest regimes via PC software |
| Tripod mounting for meter and remote sensor array |
| Ergonomic design |
| 10M extension cables available |
| Meets requirements of ISO 7243 |
APPLICATIONS
| Power Stations |
| Foundries |
| Steel works |
| Bakeries |
| Medical Surveillance testing |
OPERATION
figure
1 |
The WBGT meter measures simultaneously from three PRTD sensors for
Wet Bulb, Dry Bulb and Globe Temperatures. Sensors are manufactured to
high accuracy standards: BS 1904 and DIN 43760.
Processed
data values include:
WBGT
(indoor and outdoor)
1 Hour (TWA)
WBGT values
Relative
Humidity (%)
Dewpoint
|
|
figure 2 |
Sensors can be used either attached directly on the body of the unit
(figure 1), or remotely via 10m extension cables (figure 2). Both the
electronic unit and sensor array can be tripod mounted (tripod not
included).
|
DISPLAY
The Microtherm WBGT incorporates a large 128 x 64 pixel graphics LCD
with backlight, capable of displaying data in two modes;
| Graphical Representation - The Microtherm WBGT is the first
area heat stress instrument to offer a real-time scrolling graph of
the temperature parameters being measured |
| This display can be shown over variable time bases of 15,30,60 Et
120 minutes. This al ows the user to assess how the environment is
changing over time, without having to download to a PC. |
| Numerical values - Instantaneous values for al parameters are
displayed, combined with the hourly rolling average values. |
ALARM
An adjustable alarm threshold may be defined for one selected data
channel: WBGTtwa, WBGT,Ta or OFF.
An audible alarm and flashing visual message on the display screen
provides warning of excedence of the threshold.
SIMPLE
KEYPAD OPERATION
The Microtherm WBGT has been designed with a simple, easy to use menu
structure for the displaying of information, instrument configuration
and retrieval of data. The access of this menu via the touch keypad and
screen prompts, ensure ease of use for the operator.
SOFTWARE
Windows 32 bit PC software package (Win HSM) provides an interface
for data collection to PC for retrospective analysis. It produces
graphical and tabular reports which can easily be imported into other
applications. Summary and WBGT Heat Stress Index reports also generated.
Work rest regimes are calculated, Clothing (Clo) correction factors,
and metabolic rates can be entered in accordance with OSHA and 1507243.
Data can also be viewed "live" by selection of the
real-time option whilst connected to the PC.
CALIBRATION
Calibration of the Microtherm WBGT is performed against an internal
reference prior to every single measurement. This ensures a high
accuracy for each of the temperature sensors and eliminates the need for
annual recalibration.
Sensor arrays are also interchangeable without need for
recalibration.
Microtherm Heat Stress WBGT kit
includes:
| Microtherm Heat Stress WBGT meter Sensor array |
| Pack of spare wicks and screwdriver Rechargeable batteries (x4) |
| Universal mains PSU (110/240vAC) with UK,Europe and USA plug adaptors. |
| Distilled water container |
| RS232 communication cable Windows Win HSM software |
| Hard carrying case |
SPECIFICATIONS
|
IDENTITY |
SENSOR
SPECIFICATION |
|
|
PARAMETER |
RANGE |
ACCURACY |
|
Ta |
Air
Temperature |
10-60ºC |
+/- 1ºC |
|
Tg |
Globe
Temp |
20-120ºC |
+/- 0.5ºC (20-50)
+/- 1.0ºC (50-120)
|
|
Tnw |
Natural
Wet |
5 to 40ºC |
+/- 0.5ºC |
|
DISPLAYED
DATA VALUES |
|
Ta |
Air
temperature |
|
Tg |
Globe
temperature |
|
Tnw |
Natural
wet temperature |
|
WBGT |
Inside
and Outside |
|
Time
Weighted WBGT values |
Based
on a 1 hr rolling average updated every 30 seconds
(During
the first hour ‘- - ‘ is displayed.) |
|
%RH |
Based
on "ta" and non aspirated "tnw" sensor |
|
Dewpoint |
Based
on "ta" and non aspirated "tnw" sensor |
|
DATA
LOGGER |
|
Total
record capacity |
512k
memory providing up to 49,100 data records |
|
Number
of runs stored |
32 |
|
Logging
interval |
30
seconds to 1 hour |
|
SOFTWARE |
|
Operating
System |
MS
Windows 95/98 NT compatible.
RS232
serial port, 8MB RAM, FDD, HDD, VGA Graphics |
|
POWER |
|
Battery
Power supply |
4
x AA cells Dry cels or Ni Cd (4.8v/950mAh)
30hrs
Nicad / 85hrs alkaline
Battery
monitoring warning and auto power down
Consumption:
30mA typical |
|
External
Power supply |
3.5
to 14VDC (12v nominal)
90-260vac
Universal input mains power adaptor
Internal
fast charge circuitry |
|
COMMUNICATIONS |
|
|
RS232
/ IRDA future expansion |
|
APPLICABLE
STANDARDS |
|
|
ISO
7243/7726
OSHA |
|
OPERATING
TEMPERATURE RANGE |
|
Sensors |
-5
ºC to +120ºC |
|
Electronics |
-5
to 60ºC |
|
Dimensions |
Instrument:
245 x 95 x 50mm
Array:
90H x 225 x 65mm
Sensor/carry
case (H x W x D): 135 x 490 x 370mm |
|
Weight |
Sensor/carry
case 0.97kg
Instrument
only 0.75kg |
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