*

2. Testing and Measurement Techniques and Procedures 

	Factors in the measurement of radiation or laser energies (frequency, wavelength, power density)
			1. Magnitude of the measured quantity
			2. The uncertainty of the measurment
			3. Damage to the measureing instrument by the radiation or laser
			4. Noise or background competing radiation
			5. Calibration of the measuring instrument
				1. Quartz halogen lamps calibrated by the National Bureau of Standards for spectral irradience between x ranges.
				2. Black body temperature based approach for making a spectral measurement - immerse black body in gold
				3. Electrically calibrated detectors - responds with a know difference to radiatn & electrical heating, the radiant power
					is measured relative to the amount of electrical power dissipated in a heater on the surface of a thermal
					detector

				
			6. Physcical standards for all wavelenghts and for all power levels
				Precision, accuracy, & certainty, Measurement process- stable & well defined
				Power and energy meters that can be electrically calibrated to mak a control 
				chart for an instrument or determine its perfromance characteristics under the
				various conditions in which it may be used.
			7. Errors of spectral measurements - Since radiation is a function of position, direction,
				wavelength, time & polarization, then since the following three measurements depends on
				the above five radiation, environmental, & instrumetnal parameters, there may be large 
				systematic errors: 
					1. The responsivity of the radiometer
					2. The radiation being measured 
					3. The radiation standard spectral distribution
			8. Out of band leakage can be avoide by using a double monochromometer


			9. Measuring instruments

				Servosystem - instruments used to control an entire system.
				Readout devices - accepts voltages or current output signals from other instruments and
					registers or records the signal by writing directly on paper, on magnetic medial, or
					on an oscilloscope. 

				A biomedical instrument enables an investigator to determine and record minute or gross
				environmental changes. Most instruments must almost always convert some physical or
				chemical parameter into an electronic voltage or current signal. The device may monitor
				or alter a physiological parameters.  What effect the experiment has on the instrument
				and vice versa. Instruments have limitations such as range, sensitivity, or frequency
				response. 

			Qualities of an instrument:

				Sufficient but not excessive range and sensitivity, linearity, a high signal to noise ratio,
				complete isolation from the system being measured and from the environment, stability,
				sufficient output that is easily read, adequate but not excessive frequency response, and
				the simplest design necessary to accomplish the purpose of the instrument. 

			Parts of an instrument:
				1. Sensing element or transducer to detect the primary signal. 
					The transducer element converts the magnitude or change in magnitude of the
					parameter to be measured into a useable electronic signal.

				2. A signal modifier or processor which is an amplifier or combination of amplifiers
				3. A device that enables the user to read and record the output signal

			Calibration of an instrument:

				1. Does the instrument, measure only the parameter being measured, affect the parameter
					being measured, have enough range to include all possible quantities of
					parameters, have enough sensitivity throughout the desired range ?
				2. Does the output of the instrument increase linearly with equal increments of the
					desired parameter.?  Determine the sensitivity and linearity of the entire system
					after other components of the system have been tested and calibrated.
				3. Does the instrument provide a sufficient signal to distinguish it from its inherent noise
					or does it have a high eouph signal to noise ratio? The smallest signal that can be
					measured is a function of the signal to noise ratio.

				4. Can the instrument respond fast enough to faithfully reproduce changes in the
					parameter being measured or does it have an adequate frequency response?
					Apply a sinusoidal voltage to the input. As the frequency is increased, the
					amplitude of the output should not decrease.  Ensure that the highest frequency
					component in the data to be measured is not attenuated more than the usual
					allowance of 5 percent.  The higher the frequency response of the equipment, the
					higher the cost of the equipment. 

				5. Determine all the factors that may have some effect on the system. Is current allowed
					to flow through the patient to or from ground. 

				Almost all biomedical parameters are difficult to isolate from their environment. A living
				organism is a bag of salt water as far as biomedical instrumentation is concerned. 

3. Biometrics, Bioinformation, Biocommunication		

	Self regulating system
		Feedback control system
			Biotransmitter > Biocommunication > Biosensors
			
 				Basic energy frequencies in communication competition with one another:
	
				Thermal energy frequencies
				Magnetic energy frequencies
				Electrical energy frequencies


				 

			
				


 


[Top of Document]