Engineering 1620 – Spring 2012 Laboratory Hints and Corrections
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1. Engineering 1620 Spring 2012 Laboratory Hints and Corrections Here are some hints about the labs and some additions to instructions and questions that I have put together because of changes after the manual was written I am putting actual corrections into the on line lab manual as I find them This list is organized by lab number and I hope to update it throughout the semester Lab 1 1 We have new Agilent DSOX2012A oscilloscopes Two of them are set up on the back bench with the function generators for Lab 1 The full user manual for this scope is now on the computers in the lab under the start menu at Start All Programs Agilent Intuilink 2000_Series User Manual It is also posted as a handout on the ENGN1630 class website These machines have the ability to capture screen data in any of several file formats on a USB flash drive To use this capability after you have the measurement displayed on the screen e Insert a flash drive into the USB connector at the bottom center of the front panel e Hit the File Save button at the bottom of the Measure group of controls e The screen will show new labels above the buttons at the bottom of the screen Hit the Save button to open some additional softbutton choices o Select the CSV Comma Separated Values data format o Select Filename and enter the name you want to use to store the image o Hit Save to store the screen data to the drive Remember the TAs ha2. g hpg There is usually not a very large difference between the differential and B whole ratios but at very low and very high currents they can differ by as much as a factor of 2 which is why the distinction is made As a reminder B h and Io Br 20 Ip 1 p a Determining the Early voltage from the IC vs VCE data is a bit tricky because the fit is inexact The intercept of the extended IC vs VCE line is actually a function of the EGN1620 Lab Hints and Corrections Spring 2012 collector current rather than an exact constant I have found that the intercept is reasonably constant for currents in the range of 1 10 mA and collector voltages of 2 to 15 volts Here is a plot of some data showing that range IC vs VCE for 2N222A with Fit of Early Effect with Fixed Early Voltage 2 00E 02 1 50E 02 a A gt Z 3o 1 00E 02 G w m Eua 5 00E 03 p U wv w 0 00E 00 0 0 5 0 10 0 15 0 20 0 VCE volts Labs 4 5 The Bode plotter is easy to use with these instructions 25 0 B 10u B 20u B 30u B 40u B 50u B 60u B 70u fit IB 10u fit IB 20u Fit IB 30u Fit IB 40u Fit IB 50u Fit IB 60u Fit IB 70u 1 Set your lab up to operate with the power supply that is on the shelf above the Bode plotter and get it runnin
3. g 2 Turn on both the function generator and the gain phase meter Please do not tinker with the cables Note that cabling is different for the two experiments The settings on the gain phase meter are Both inputs set for 2mV 20V Phase set to A Frequency range 10 100 KHz Function B A EGN1620 Lab Hints and Corrections Spring 2012 3 In Windows Explorer go to D TestSoftware en162 en162bodeplotter and run Exp4 bat or Exp5 bat as appropriate Enter your protoboard serial number and let the program run to completion 4 Microsoft EXCEL will open with data from the last user when the measurements finish The spreadsheet has a macro to import and display your data that has to be enabled with the Options button 5 Select the sheet with the data the tab is temp_bode Hit the Import Data softbutton Your data will be imported and you can then save this spreadsheet to the U drive for the lab writeup 6 Have a TA give you the magic number for this run
4. rement points near zero by connecting a 1 0 K resistor across the multimeter attached to the back terminals Without the resistor the measurement range is zero to 120 volts and with it the range is zero to 6 volts There is a 21 K resistance in series with the power supply I have put a mounted resistor on the meter leads that can be plugged and unplugged depending on what voltage range you need Please do not lose that little piece The software to run the HP4145B parameter analyzer is on the D drive of the computer next to the analyzer To find it browse to D Test Software En162 and double click on par_analyze exe To find ideality constants from the Gummel plot you will need the junction temperature Please be sure to record the temperature of the environment at the time you do your tests There is a digital thermometer on the shelf over the analyzer I know that such toys are attractive but please don t steal it ve had that happen twice and it is really unfair to other people and a nuisance for me The accepted value of y is 86 17 microvolts per degree K and 0 degrees C is 273 15 degrees K A brief word about the subscripts on alpha beta and hg or hre Lowercase subscripts I gt Al indicate differential quantities e g h Be Sla These are usually measured by dI Al measuring the change in quantity for a relatively small change 20 to 40 in the denominator quantity Uppercase subscripts mean whole quantity ratios as e
5. ve to see you do at least one such operation to give you your magic number When you are trying to determine the output impedance of the voltage source you do not want the complication of the waveform changing shape as you change the load on the source Applying a simple voltage divider relation to the signal only makes sense if its spectrum does not change as the divider is formed The 10X probe does not load the circuit with sufficient capacitance to affect the waveform seriously Use the 10X probe when doing that part of the experiment NOT the 1X probe When you use the 1X probe the waveshape changes dramatically as you connect a load resistor Why EGN1620 Lab Hints and Corrections Spring 2012 Lab 2 1 There is one high voltage power supply 120 VDC max wired to the bias terminals of the capacitance meter through a resistor and zener diode network mounted on the back of the meter to protect the meter and the supplies Please do NOT remove that circuit We also have a multimeter connected to the back terminals of the capacitance meter to make voltage measurements easier You may use a second meter to check polarity on the front terminals but please leave the main meter alone The relatively high voltage power supply 120 VDC on the capacitance meter is not easily adjusted to produce low test voltages Because of the safety network on the back of the analyzer you can get a much lower effective supply voltage for the measu
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