Glossary of Instrument Systems
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- what are the components in an instrument system?
- -Input transducer
- what is a transducer?
- device to convert energy or info from one form to another.
- What does an Input transducer do?
- detects the magnitude of the quantity being measured.
- What are 3 examples of input transducers?
- 1. Photovoltaic cell (light energy to electrical)
2. Electrode (chem to electrical energy
3. Thermistor (thermal energy to electrical)
- What is an output transducer?
- the component that recieves the signal from the input transducer and displays the measurement.
- what are 2 examples of output transducers?
- 1. Meter
- What is a signal modifier?
- Device that recieves input transducer data and changes it to a form suitable for the output transducer.
- what are 5 examples of signal modifiers?
- 1. amplifier
2. log to linear convertor
3. Analog to digital converter
- what are the two things used to calibrate an instrument system?
- 1. Zero control
2. Amplifier gain
- what is zero control for?
- getting rid of dark current.
- What is photometry?
- the measurement of light
- what are 4 ways to measure light with photometry?
- 1. Absorption
- what type of measurement is spectrophotometry and atomic absorption?
- what are 3 types of emission photometry?
- what is the principle of reflectance photometry?
- Sample gets adsorbed to a reflective surface, amount of liht reflected is 1/Conc of the sample.
- What is nephelometry?
- the measurement of light scattered by particles in a solution.
- what is light?
- segment in the spectrum of electromagnetic radiation that may or may not be visible to us.
- what is the range..
- IR = 700-2000 nm
Vis = 400-700 nm
UV = 180-400 nm
- what are longer waves, Red or Violet?
- Violet = short waves, hi energy
Red = long waves, low energy
- What is color?
- the wavelength of light NOT absorbed bysomething, but transmitted
- What is the principle of absorptivity?
- Incident light passes through a sample; the light NOT absorbed gets TRANSMITTED.
- What is a transmittance curve, and what does it show?
- Curve that shows the specificity and sensitivity of a particular wavelength for a sample.
- How do you use a %T curve?
- by scanning the wavelengths, then selecting the highest %T because that gives the optimal sensitivity and specificity.
- What are the variables in beer's law?
A = absorption
a = absorptivity constant
b = sample path - cuvette width
c = analyte concentration
- what are the components in a spectrophotometer?
- 1. Power supply
2. Light source
5. Photodetector - Input Trans
6. Amplifier/Signal modifier
7. Readout device - output transducer
- What are some requirements for the power supply?
- -voltage has to be DC, not AC
-Has to be divided.
-Constant and well regulated.
- What are some requirements for the light source?
- -Intense light source
-Steady, cool, easily colimated
-Directs at sample w/ lens
- What are 3 types of light sources?
- 1. Visible - Tungsten
2. UV - Gas
3. IR - Scanning laser diode
- what is a monochromator?
- it isolates light of a single color from an impure source.
- what are 3 types of monochromators?
- 1. prism
2. Diffraction grating
- what are 3 types of prisms, what are they for?
- Glass - visible light
Quartz - UV
Fused silica - UV
- How does a diffraction grating act as a monochromator?
- it bends light as it passes through a tiny slit.
- what are 2 types of diffraction gratings?
- 1. Reflectance
- what are 2 types of filters?
What are filters used for?
- 1. Absorption - it absorbs unwanted wavelengths.
2. Interference - it uses CONSTRUCTIVE interference to produce the desired wavlngth.
Typically used for colorimeters
- What is the bandpass?
- the range of wavelengths at which %T is one half its max.
- What does bandpass tell?
- the quality of diffraction grating - the quality of light passing through the sample.
- What types of cuvettes are used for
- Vis = glass
UV = Quartz or plastic
- What can be used as the input transducer in a spec?
- -Photovoltaic cell
- What can be used as a readout device?
-Null balance (wheatstone)
- What are the types of spectrophotometers?
- 1. Single beam
2. Double beam
- what wavelength does IR spectroscopy measure at?
- 690-1000 nm
- what is IR spectroscp?
- IR light makes molecules vibrate, transmitting very characteristic light.
- what are some clinical applications of IR spec?
- -Msr through thick tissue - blood glucose for diabetics
-Blood CO2 cultures
- what is an agricultural use of IR spec?
- Measuring maturty of apples
- what are 4 types of light measurement other than spectrophotometric?
- 1. Nephelometry
3. Reflectance photometer
4. Fiber optics
- what's different about the construction of the nephelometer?
- the light detector (input transducor) is at an angle that is NOT 180 degrees from the sample.
- What two types of light sources are used in nephelometry?
- 1. Tungsten
- what are 3 applications of nephelometry?
- Amylase Lipase analysis
- What is a refractometer?
- an instrument that measures the refractive index of a solution
- what is the refractive index?
- a number related to the quantity, charge, and mass of vibrating particles in a solution.
- What are 3 applications of refractometry?
- -Grams protein
-Electrophoreis - need to know total protein in serum.
-Dipsticks for urine.
- What is reflectance photometry?
- dry slide technology that measures light reflected from a reflective surface w/ sample adsorbed onto it.
- how do you figure out concentration of sample from reflectance photometry?
- Light reflected = 1/conc.
- What is a clinical application of reflectance photometry?
- the dipstick reader to eliminate variation between techs.
- what's the name of that reflectance photometer?
- the VITROS
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