Study of Technology for Detecting Pre-Ignition Conditions of ... - NIST

CPSC-HG95-1145
the doorway of the laboratory enclosure and was focused to capture a view of the entire cooking
scene including the range surface, cooking pan, range hood, and smoke plume. The abilities to
zoom close to the pan as well as achieve panoramic views were important features of the camera.
A Ricoh lvlirrai zoom lens camera was used to take still 35 mm slide photographs of the
apparatus and test behavior.
2.3 Ilata ~~~~isiti~~, ~e~~etio~, and Plotiing
2.3.1 Data Acquisition
An Intel 486 computer controlled the data acquisition process. The computer
mmmunicated with an FIP3460 scanner box and HP3454A digital voltmeter. The data system
has a capacity of 20 instrument channels and 60 thermocouple channels, but only 3 and 24 were
used, respectively. Approximately one second of scan time is required for every 20 channels
used. The data system was capable of scanning the 27 channels at two second intervals which
was the setting for a few tests, but most of the tests used a three second time interval.
A data acquisition program developed at the Building and Fire Research Laboratory was
executed on the computer. The program requires input of instrument channel range,
themnocouple channel range, scan interval, display preference, and file name. The program
allows the user to take sets of “zero” and “span” readings of the instrument voltages for purposes
of calibration. For this series of tests, only a set of background zeroes, the output voltages for
ambient conditions, was necessary. The data were stored on the computer hard disk in a format
compatible with the data reduction program.
The FTIR spectrometer was controlled and the data were acquired with a dedicated Intel
386 computer. The FTIR scanned 64 times and produced average signals from the scans every
20 seconds. Initially, FTIR data were taken in the absorbance mode, but problems with data
collection in this mode necessitated switching to collection of data in the single-beam mode which
was then converted to the absorbance mode after each test using the data processing routines
within the FTIR software.
2.3.2 Data Reduction
The reduction of data was acmmplished with the WID software which was developed
at NIST especially for fire tests. 7 RAPD consists of a set of FORm subroutines that convert
voltages from instrumentation and thermocouples into meaningful physical values. Subroutines
are also available to further convert and combine basic variables into more useful forms. The
main subroutines used for these experiments were TC to convert thermocouple voltages to
temperatures, VELOCITY to convert the pressure transducer voltage into velocity, CONIIWTE
which combines any other channels arithmetically as desired, and SMOOTH which is described
in Section 2.3.3.
Instrument descriptions and calibrations are entered and the subroutines are accessed
through a control file with extension “.ctl”. A sample control file is included in Appendix D.
The control file specifies the treatment of the raw data and the output format. Each data file
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