Equipment Required: . . DIGIAC 1750 Transducer and Instrumentation Trainer. 4mm Connecting Leads. Digital Multimeter. •

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: Equipment Required Digiac 1750 Transducer And Instrumentation Trainer 4mm Connecting Leads Digital Multimeter 1 (151.98 KiB) Viewed 42 times

Equipment Required: . . DIGIAC 1750 Transducer and Instrumentation Trainer. 4mm Connecting Leads. Digital Multimeter. • Opaque box to cover the clear plastic enclosure. . 1. The PIN Photodiode Objectives: Describe the characteristics of a phototransistor sensor. Fig 1 shows the construction of the PIN photodiode. Light Light Lens Depletion Layers 11 dy 1 Intrinsic (1) Region O Hole • Electron Electron/Hole pairs generated in the I region Contacts Fig 1 construction of the PIN photodiode This differs from a standard PN photodiode by having a layer of intrinsic (pure) silicon, the I region, between the normal P and N regions. The main improvement of the introduction of the I region is a reduction in the capacitance of the junction, resulting in a faster response time which can be as high as 0.5ns. The device can be operated in one of two ways: (a) as a photovoltaic cell, measuring the voltage output, and (b) by amplifying the output current and converting it into a voltage. O/P Sensitivity 0.55A/W Current Characteristic 2856KnA/x Response Time Peak Spectral Response 850nm (IR) 3.5ns OV Characteristics of a BPX65 PIN Diode Fig 2
Fig 2 shows the circuit arrangement and characteristics for the PIN Diode mounted on the DIGIAC 1750 unit. 2. Practical Tasks: Please perform the following tasks: a. Connect the circuit as shown in Fig 3, using the Current Amplifier to measure the current output of the PIN Photodiode. MOVING COIL METER PHOTOVOLTAIC CELL P.I.N. PHOTODIODE O/P 20 O/P OPO . O/P O/P 00 888 & PHOTOCONDUCTIVE CEVI LAMP FILAMENT PHOTOTRANSISTOR IP (но AMPLIFIER #1 CURRENT AMPLIFIER WIRE WOUND TRACK O/P POWER AMPLIFIER 10 IN 3 21 1000 10 10 10kΩ +12V 0-0 OFFSET COSE GAIN FINE ov - Fig 3 b. Use the digital multimeter on the 20V DC range to measure the output voltage of Amplifier #1. Fit the opaque box over the Clear Plastic Enclosure to exclude all ambient light. c. Switch ON the power supply and set the 10k 2 wirewound resistor to minimum for zero output voltage from the power amplifier. d. Set the GAIN COARSE of Amplifier #1 to 10 and set the GAIN FINE to 1.0. Check that the OFFSET is giving zero output for zero input and adjust if necessary. e. Take readings of Amplifier #1 output voltage as indicated on the digital multimeter as the lamp voltage is increased in 1V steps. Record the results in Table 1 in the row labeled PIN Photodiode Current Amp. O/P.
0 1 2 3 7 9 10 Lamp filament voltage (volts) PIN Photodiode Current Amp. O/P PIN Photodiode Output Voltage Table 1 V V V V V V V V V V V V V V V V V V V V V V f. Change the Current Amplifier to the Buffer Amplifier to measure the output voltage of the PIN Photodiode. g. Take readings of PIN Photodiode amplified Output Voltage as the lamp voltage is again increased in 1V steps. Record the results in Table 1 in the row labeled PIN Photodiode Output Voltage. h. Plot the graphs of PIN Photodiode Current Amplifier Output Voltage and Buffered Output Voltage against Lamp filament voltage on the graticule provided. 5.5 5.0 PIN Photodiode 4.5 Output Voltage (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 1 2 3 4 5 6 7 8 9 10 Lamp Filament Voltage (volts) Figure 4
i. From your graph estimate and enter the lamp filament voltage when the circuit output voltage is 2V with the Current Amplifier connected. j. From your graph estimate and enter the lamp filament voltage when the circuit output voltage is 2V with the Buffer Amplifier connected. k. Are the two graphs similar shapes? Yes or No Instructor may ask any questions regarding the construction of the lab/results and to be documented 3. Conclusion (three to four lines only)