Glossary of 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?
what are 3 types of emission photometry?
flame 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
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
What can be used as a readout device?
-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?

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