BME 153 lab 8 Transformes and Diodes _Nigel

# BME 153 lab 8 Transformes and Diodes _Nigel - BME 153 Lab 8...

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BME 153 Lab 8 Lab 8 – Transformers and Diodes Nigel Chou Shijie Lab Partner: Tim Liu Section 1 December 5, 2007 I have adhered to the Duke Community Standard in completing this assignment. Objectives The objective of this lab is to learn to build clamping and clipping circuits using diodes and observe their properties. We will also construct a simple transformer out of wire and a metal core and learn to convert AC voltage to DC voltage using a rectifier circuit which contains both transformers and diodes. Apparatus LCR Meter Fluke 45 Dual Display Digital Multimeter (DMM) Tektronic TDS 1012 Digital Storage Oscilloscope TGS 50 Signal generator Resistors, capacitors and inductors Solderless breadboard Procedure The procedure listed in the lab manual was followed with slight deviations. For section 3.1, the threshold voltage was obtained in two ways. With the circuit of Figure 4, the voltage difference between the time-axis of the oscilloscope and the constant voltage part of the output signal is measured using the horizontal cursors. With the circuit of Figure 5, the same thing is done for both the positive and negative constant voltage parts of the output signal. This voltage difference is then divided by 2 to obtain the threshold voltage. For section 3.2, the current through the diode is found be measuring the voltage across R1 and dividing by R. For small currents, this is more accurate than using an ammeter to measure current directly. For section 3.3 parts 1 to 4, due to problems with the circuit and the transformer, we had to use a frequency of 5MHz instead of 1MHz, since the voltage across R 1 was not in phase at the lower frequency. For part 4, instead of rewinding the circuit, we switched the leads to the primary coil , thus effectively making the current go through the coil in the opposite direction, which is effectively the same as rewinding the coil in the opposite direction. Data and Calculations 3.2 Diode clamping circuit The current across the diode is calculated by: A 00 . 0 5049 00 . 0 1 1 = = = R V I R D The ratio of secondary to primary voltage is calculated by: 686 . 1 60 . 5 44 . 9 pk) (pk pk) (pk = = - - p s V V The % difference between measured and theoretical voltage ratios: % 7 . 15 % 100 2 2 .686 1 diff % - = × - = 1

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BME 153 Lab 8 The AC currents are calculated as follows: A 10 89 . 30 36 . 50 2 2 60 . 5 10 ) RMS ( 3 1 1 - × = - = = R V I R P A 10 314 . 3 1007 2 2 44 . 9 ) RMS ( 3 2 - × = = = R V I S S Power in primary coil: W 10 16 . 61 ) 10 89 . 30 )( 980
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## This lab report was uploaded on 04/09/2008 for the course BME 153 taught by Professor Malkin during the Fall '07 term at Duke.

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BME 153 lab 8 Transformes and Diodes _Nigel - BME 153 Lab 8...

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