Unihedron SQM-LU-DL-V, Operator'S Manual

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14 Glossary
Table 14.1: Glossary of terms
ADC A nalog to D igital C onverter. A device usde to convert an analog signal into a digital value.
CCD C harge c oupled d evice is a type if image sensor.
EEPROM E lectrically E rasable P rogrammable R ead O nly M emory is a type of memory that retains its
contents after the power has been removed. This type of memory has a limited write/erase cycle
as well as a lifetime for data retention. In the SQM-LU-DL-V, the parameters in the micro-
controller can be written 1 million times and last for 100 years.
Firmware The program that resides inside the device. In the case of the Unihedron SQM products, it is
the software runs the device including reading and reporting the light values.
FITS F lexible I mage T ransport S ystem is an open standard defining a digital file format useful for
storage, transmission and processing of scientific and other images.
FTDI F uture T echnology D evices I nternational is the manufacturer of the USB module inside the
SQM-LU-DL-V. FTDI also supplies the VCP software driver for the computer operating system
so that the SQM-LU-DL-V can communicate with the computer.
GPS G lobal P ositioning S ystem. A GPS receiver may be connected to a computer to allow UDM to
integrate the location information into the logged data. See UDM for mode details.
mpsas M agnitudes p er s quare a rcsecond. The unit of measurement reported by the SQM.
NMEA N ational M arine E lectronics A ssociation data format that the GPS receiver produces.
RAM R andom A ccess M emory. Temporary memory that only retains data while power is applied.
RTC R eal T ime C lock. A circuit that is used to keep “real time” data like date/time. Computations
for leap year and weekday are performed in this circuit.
SQM-LU-DL-V S ky Q uality M eter with L ens and U SB connectivity, and with d ata l ogging capabilities, and
with the V etcor measurements Altitude (inclinometer) and Azimuth (compass).
Supercap A very large capacitor in the order of Farads. The SQM-LU-DL-V uses a supercap to keep the
RTC running when the meter is not connected to any external power supply. The advantage of
this component no internal battery must be regularly replaced.
The disadvantage is that the capacitor must be occassionally charged up before using the meter
for external battery assisted datalogging. When fully charged (a few hours), the capacitor will
last for weeks.
UDM U nihedron D evice M anager is software used to access the SQM series of meters.
USB U niversal S erial B us
UTC Coordinated Universal Time is the primary time standard by which the world regulates clocks
and time.
VCP V irtual C OM p ort (VCP) drivers cause the USB device to appear as an additional COM port
available to the PC. Application software can access the USB device in the same way as it would
access a standard COM port. The SQM-LU-DL-V requires the FTDI VCP driver be installed
on the computer operating system so that communications can be done with the meter.
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