accuracy
absence of bias

Beer Lambert Law
The light transmitted through a solution changes in an inverse logarithmic relationship to the sample concentration.

Colorimetric measurement
Measurement is made using a light source which has a known wavelength. This incident light then passes through a cuvette containing a chemical compound in solution. The intensity of the light leaving the sample will be less than the light entering the cuvette. The loss of light or absorption is proportional to the concentration of the compound.

data compression
Storing data in a format that requires less space than usual. Data compression is particularly useful in communications because it enables devices to transmit or store the same amount of data in fewer bits. There are a variety of data compression techniques, but only a few have been standardized. The CCITT has defined a standard data compression technique for transmitting faxes (Group 3 standard) and a compression standard for data communications through modems (CCITT V.42bis). In addition, there are file compression formats, such as ARC and ZIP.

detector
The detector determines how much light was transmitted through the sample for correlation to concentration.

dose
stimulus

EXE file
Pronounced ee-ex-ee file. In DOS and Windows systems, an EXE file is an executable file with an .EXE extension.

executable file
A file in a format that the computer can directly execute. Unlike source files, executable files cannot be read by humans. To transform a source file into an executable file, you need to pass it through a compiler or assembler. In DOS systems, executable files have either a.COM or.EXE extension and are called COM files and EXE files, respectively.

extension
In DOS and some other operating systems, one or several letters at the end of a filename. Filename extensions usually follow a period (dot) and indicate the type of information stored in the file. For example, in the filename EDIT.COM, the extension is COM, which indicates that the file is a command file.

filter
The filter removes all light except the wavelengths used for the analysis.

LED
Light Emitting Diodes

light source
Light Emitting Diodes (LED's). The advantage of using LED's as a light source is longer battery life and its temperature stability which does not shift wavelength with changes in temperature.

OD
Optical density units also known as absorbance (A). Optical density (absorbance) is used for colorimetric analysis so that readings relate directly to concentration.

precision
The statistical error in the dose measurement.

RS-232C
Short for recommended standard-232C, a standard interface approved by the Electronic Industries Alliance (EIA) for connecting serial devices. In 1987, the EIA released a new version of the standard and changed the name to EIA-232-D. And in 1991, the EIA teamed up with Telecommunications Industry association (TIA) and issued a new version of the standard called EIA/TIA-232-E. Many people, however, still refer to the standard as RS-232C, or just RS-232. Almost all modems conform to the EIA-232 standard and most personal computers have an EIA-232 port for connecting a modem or other device. In addition to modems, many display screens, mice, and serial printers are designed to connect to a EIA-232 port. In EIA-232 parlance, the device that connects to the interface is called a Data Communications Equipment (DCE) and the device to which it connects (e.g., the computer) is called a Data Terminal Equipment (DTE). The EIA-232 standard supports two types of connectors -- a 25-pin D-type connector (DB-25) and a 9-pin D-type connector (DB-9). The type of serial communications used by PCs requires only 9 pins so either type of connector will work equally well.

Sensitivity
The minimal detectable concentration or the slope of the dose–response standard curve or the ratio of the response of a device to the stimulus.

Transmittance (T)
The transmission of light and its absorbance have very specific meanings. These are: Transmittance (T) = Light transmitted (I)/Incident light (I0) Absorbance = Log (1/T) = abc "a" is a constant - the ability of a given molecule to absorb a particular wavelength of light. "b" is the path length - the longer the path, the less light gets through. "c" is the concentration - the more molecules in the solution, the more light is absorbed. To get a straight line calibration curve, absorbance VS. concentration needs to be plotted. The equation of colorimetry used for the calibration curve is Beer's Law. where: Beer's Law is the Transmitted light = Initial light x 10(-abc)

Turbidity
Turbidity is the interaction between light and suspended particles in water. It is a qualitative measurement because the reflection and scattering of light from particles depends on the nature of the particular particles. Particle size and shape affect the direction and intensity of the scattered light, as will its color, and how transparent or reflective it is. The scattering intensity and direction of scatter also changes with the wavelength of the incident light. In general, the greater the intensity of scattered light, the higher the turbidity, it is not possible to quantitatively estimate particle concentration unless the particles are uniform and reproducible. Turbidity is measured in units of NTU (Nephelometric Turbidity Units), or in units of FTU (Formazine Turbidity Units), depending on the calibration standard used.

zero
Sample blanks and zeros correct for stray light, sample color or turbidity, or absorption of the measured wavelength by some constituent of the sample, and to correct for internal reflection of light by container walls.

ZIP file
A popular data compression format. Files that have been compressed with the ZIP format are called ZIP files and usually end with a.ZIP extension.