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| university:courses:electronics:electronics-lab-breadboard-coupling [04 May 2014 02:28] – [Extra Credit work:] Doug Mercer | university:courses:electronics:electronics-lab-breadboard-coupling [24 Jul 2017 14:58] – change amplitude value to peak-peak Antoniu Miclaus |
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| When there are unintended hidden capacitors in the structure of the circuit being tested, we refer to these as parasitic capacitance. The solder-less breadboard has a lot of these unwanted parasitic capacitances. These stray paths can lead to unwanted coupling between inputs and outputs in the breadboarded circuit. Take the standard single op-amp in an 8 pin DIP package for example. The inverting and non-inverting inputs are right next to each other on pins 2 and 3. Another example would be the standard dual op-amp in an 8 pin DIP where the output of one of the amplifiers is on pin 1 and its inverting input is on the adjacent pin 2. When inserted in the breadboard a small stray capacitance will be present between these two pins which can adversely affect the circuit characteristics at high frequencies. | When there are unintended hidden capacitors in the structure of the circuit being tested, we refer to these as parasitic capacitance. The solder-less breadboard has a lot of these unwanted parasitic capacitances. These stray paths can lead to unwanted coupling between inputs and outputs in the breadboarded circuit. Take the standard single op-amp in an 8 pin DIP package for example. The inverting and non-inverting inputs are right next to each other on pins 2 and 3. Another example would be the standard dual op-amp in an 8 pin DIP where the output of one of the amplifiers is on pin 1 and its inverting input is on the adjacent pin 2. When inserted in the breadboard a small stray capacitance will be present between these two pins which can adversely affect the circuit characteristics at high frequencies. |
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| Schematically we can view the breadboard and our measurement setup as shown in figure 2. In the figure we depict three typical rows of pins on the breadboard. The row to row capacitance, C<sub>row</sub>, is shown. Since all the rows are more or less identical, all the C<sub>row</sub>s have the same value. To measure Crow we will excite one row with the AWG sine source and measure the amount of signal coupled onto another row (an adjacent row in this schematic) using the oscilloscope. We will model the oscilloscope channel as a 1 megaohm resistance, R<sub>m</sub>, to ground in parallel with some as yet unknown capacitance C<sub>m</sub>. The 1 megaohm value for R<sub>m</sub> is only an approximation. If you have a digital ohm meter use it to get the actual R<sub>m</sub> for your Discovery module. The wiring that connects the AWG and Scope inputs to the breadboard also introduce some stray coupling capacitance which is included as C<sub>stray</sub> in the schematic. | Schematically we can view the breadboard and our measurement setup as shown in figure 2. In the figure we depict three typical rows of pins on the breadboard. The row to row capacitance, C<sub>row</sub>, is shown. Since all the rows are more or less identical, all the C<sub>row</sub>s have the same value. To measure Crow we will excite one row with the AWG sine source and measure the amount of signal coupled onto another row (an adjacent row in this schematic) using the oscilloscope. We will model the oscilloscope channel as a 1 megaohm resistance, R<sub>m</sub>, to ground in parallel with some as yet unknown capacitance C<sub>m</sub>. The 1 megaohm value for R<sub>m</sub> is only an approximation. If you have a digital ohm meter use it to get the actual R<sub>m</sub> for your ADALM2000 module. The wiring that connects the AWG and Scope inputs to the breadboard also introduce some stray coupling capacitance which is included as C<sub>stray</sub> in the schematic. |
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| {{ :university:courses:electronics:abc_f2.png?575 |}} | {{ :university:courses:electronics:abc_f2.png?575 |}} |
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| ===== Materials: ===== | ===== Materials: ===== |
| Analog Discovery Lab Module\\ | ADALM2000 Lab Module\\ |
| Solder-less Breadboard\\ | Solder-less Breadboard\\ |
| Fly-Wire connector\\ | Fly-Wire connector\\ |
| ===== Step 1 Directions: ===== | ===== Step 1 Directions: ===== |
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| The first step is to measure just the stray capacitance, C<sub>stray</sub>, between the AWG output and Scope input due to the Fly-Wire connector. Connect the wires from the Discovery module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 3. The two scope minus inputs 1- and 2- are both grounded. Scope channel 1+ input is tied to the AWG 1 output, W1, using one row on breadboard. Scope channel 2+ is inserted into a bread board row at least 10 rows away from the row that the AWG output is inserted in. The row adjacent to scope channel 2+ and towards the AWG1 row is grounded. Because the Fly-Wires are not shielded, try to keep the W1 and 1+ wires as far away from the 2+ wire as possible. | The first step is to measure just the stray capacitance, C<sub>stray</sub>, between the AWG output and Scope input due to the Fly-Wire connector. Connect the wires from the ADALM2000 module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 3. The two scope minus inputs 1- and 2- are both grounded. Scope channel 1+ input is tied to the AWG 1 output, W1, using one row on breadboard. Scope channel 2+ is inserted into a bread board row at least 10 rows away from the row that the AWG output is inserted in. The row adjacent to scope channel 2+ and towards the AWG1 row is grounded. Because the Fly-Wires are not shielded, try to keep the W1 and 1+ wires as far away from the 2+ wire as possible. |
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| {{ :university:courses:electronics:abc_bb1.png?600 |}} | {{ :university:courses:electronics:abc_bb1.png?600 |}} |
| ===== Hardware Setup: ===== | ===== Hardware Setup: ===== |
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| Using the Network Analyzer instrument in the Waveforms software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz. Scope channel 1 is the "filter" input and scope channel 2 is the "filter" output. Set AWG offset to 0 and the Amplitude to 1V with the Max-Gain set to 0.1X. Set the vertical scale to start at 1dB with an 80 dB range. Run a single sweep and export the data to a .csv file. | Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz. Scope channel 1 is the "filter" input and scope channel 2 is the "filter" output. Set AWG offset to 0 and the Amplitude to 2V with the Max-Gain set to 0.1X. Set the vertical scale to start at 1dB with an 80 dB range. Run a single sweep and export the data to a .csv file. |
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| ===== Procedure: ===== | ===== Procedure: ===== |
| ===== Step 2 Directions: ===== | ===== Step 2 Directions: ===== |
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| The second step is to measure just the single row capacitance, C<sub>row</sub>, between adjacent rows with the second adjacent row floating. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the Discovery module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 4. Starting from the figure 3 configuration all you need to do is move the blue 2+ scope input wire to the row next to where AWG1 and scope 1+ wires are connected. The second black ground wire can be connected with the rest of the grounds tied to the bus strip. | The second step is to measure just the single row capacitance, C<sub>row</sub>, between adjacent rows with the second adjacent row floating. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the ADALM2000 module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 4. Starting from the figure 3 configuration all you need to do is move the blue 2+ scope input wire to the row next to where AWG1 and scope 1+ wires are connected. The second black ground wire can be connected with the rest of the grounds tied to the bus strip. |
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| {{ :university:courses:electronics:abc_bb2.png?600 |}} | {{ :university:courses:electronics:abc_bb2.png?600 |}} |
| ===== Hardware Setup: ===== | ===== Hardware Setup: ===== |
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| Leave all the settings the same as in step 1. Using the Network Analyzer instrument in the Waveforms software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a second .csv file with a different name. | Leave all the settings the same as in step 1. Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a second .csv file with a different name. |
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| ===== Procedure: ===== | ===== Procedure: ===== |
| ===== Step 3 Directions: ===== | ===== Step 3 Directions: ===== |
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| The third step is to measure the single row capacitance, C<sub>row</sub>, between adjacent rows with the second adjacent row grounded. This places a C<sub>row</sub> in parallel with C<sub>m</sub>. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the Discovery module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 5. Starting from the figure 4 configuration all you need to do is move the second black ground wire from the ground bus to the row to the left (opposite side) of the row that the blue 2+ scope wire is plugged into. | The third step is to measure the single row capacitance, C<sub>row</sub>, between adjacent rows with the second adjacent row grounded. This places a C<sub>row</sub> in parallel with C<sub>m</sub>. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the ADALM2000 module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 5. Starting from the figure 4 configuration all you need to do is move the second black ground wire from the ground bus to the row to the left (opposite side) of the row that the blue 2+ scope wire is plugged into. |
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| {{ :university:courses:electronics:abc_bb3.png?600 |}} | {{ :university:courses:electronics:abc_bb3.png?600 |}} |
| ===== Hardware Setup: ===== | ===== Hardware Setup: ===== |
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| Leave all the settings the same as in steps 1,2. Using the Network Analyzer instrument in the Waveforms software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a third .csv file with a different name. | Leave all the settings the same as in steps 1,2. Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a third .csv file with a different name. |
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| ===== Procedure: ===== | ===== Procedure: ===== |
| ===== Step 4 Directions: ===== | ===== Step 4 Directions: ===== |
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| The fourth step is to measure the combined capacitance, C<sub>row</sub>, with adjacent rows on both sides of a row driven by AWG1. This places two C<sub>row</sub> in parallel so the coupling capacitance is now 2C<sub>row</sub>. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the Discovery module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 6. Starting from the figure 5 configuration all you need to do is to remove the second black ground wire and return it to the ground bus and add a short jumper wire from the row to the left of the row that the blue 2+ scope wire is plugged into to the row that AWG1 and Scope 1+ are connected. | The fourth step is to measure the combined capacitance, C<sub>row</sub>, with adjacent rows on both sides of a row driven by AWG1. This places two C<sub>row</sub> in parallel so the coupling capacitance is now 2C<sub>row</sub>. Remember that C<sub>stray</sub> is still present in this measurement. Connect the wires from the ADALM2000 module to your solder-less breadboard using the fly-wire connector that came with the Kit as shown in figure 6. Starting from the figure 5 configuration all you need to do is to remove the second black ground wire and return it to the ground bus and add a short jumper wire from the row to the left of the row that the blue 2+ scope wire is plugged into to the row that AWG1 and Scope 1+ are connected. |
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| {{ :university:courses:electronics:abc_bb4.png?600 |}} | {{ :university:courses:electronics:abc_bb4.png?600 |}} |
| ===== Hardware Setup: ===== | ===== Hardware Setup: ===== |
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| Leave all the settings the same as in steps 1,2,3. Using the Network Analyzer instrument in the Waveforms software obtain a gain ( attenuation ) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a fourth .csv file with a different name. | Leave all the settings the same as in steps 1,2,3. Using the Network Analyzer instrument in the Scopy software obtain a gain ( attenuation ) vs. frequency plot from 10 Hz to 10 MHz by running a single sweep and export the data to a fourth .csv file with a different name. |
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| ===== Procedure: ===== | ===== Procedure: ===== |
