Instrument Systems

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what are the components in an instrument system?: -Input transducer
-Signal modifier
-Output 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
2. Recorder
3. Chart
4. Galvanometer
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
4. Integrator
5. Waveshaping
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
2. Emission
3. Reflectance
4. Nephelometry
what type of measurement is spectrophotometry and atomic absorption?: absorption
what are 3 types of emission photometry?: luminescence
flame photometry
fluorescence
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.. Visible: 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=abc
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
3. Monochromator
4. Cuvette
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
3. Filter
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
2. Transmission
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 -Visible spectrum -UV light: Vis = glass
UV = Quartz or plastic
What can be used as the input transducer in a spec?: -Photovoltaic cell
-Phototube
-PMT
-Phototransistor
What can be used as a readout device?: -Galvanometer
-Meter
-Null balance (wheatstone)
What are the types of spectrophotometers?: 1. Single beam
2. Double beam
-in time
-in space
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
-Pulse oximeter
-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
2. Refractometer
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
2. Laser
what are 3 applications of nephelometry?: Amylase Lipase analysis
Immunoglobulin determination
Hematology counters
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
-Specific gravity
-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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