Getting started with Mobile Studio.

Transcription

1 Getting started with Mobile Studio. IMPORTANT!!! DO NOT PLUG THE MOBILE STUDIO BOARD INTO THE USB PORT YET. First Lab: For the first lab experiment you will essentially play with the Mobile Studio Board and Software. Since this lab is fairly new to the ECE curriculum we will go over installation and use of a new USB based hardware platform. In future semesters this will be done in an earlier lab course. Note all the files linked from this document are also stored locally in the Mobile Studio Board Files folder on the ECOW2 website for this lab. Documentation files are also in this folder. You should use the ECOW2 site for download because it is faster. Procedure 1. Installing mobile studio desktop. IMPORTANT!! Install the software before connecting the board to the computer. The files are available on the ECOW2 ECE270 website. Use ECOW2 because it is faster. The files you need are in the folder named Mobile Studio Board Files. This is the original source for the Mobile Studio desktop software Calibrate the Mobile Studio: Why? For most measurements we want to know what the real voltage is. An A/D converter simply compares the voltage to be measured to a known voltage. Usually the known voltage is only accurate to about 1%. It can be more accurate but the cost goes way up so we don t usually find accurate DC references on inexpensive measurement systems. To allow measurements more accurate than 1% we can adjust the parameters of the measurement system to give the correct answer based on a real accurate measurement device. A 6 digit multi-meter is a good choice as this measurement standard. You can use an HP34401A Multi-meter to calibrate your much lower cost measurement system. You can also use the Mini DVM in your kit. There is a word and PDF document called Calibration technique for the Mobile Studio Red 2 board in the same folder that contains the Mobile studio software. 3. Setup op a quick measurement using Mobile Studio Desktop: Start up the Mobile Studio Desktop application. Click on the Oscilloscope Icon. The entire screen should look like a scope display with changeable input below the scope display region and adjustable time base and triggering settings to the right of the scope display region. I strongly suggest you right click on the Bar at the top of the Oscilloscope app and choose Auto-Hide. This will cause the window to hide. Place the mouse pointer over the smaller Oscilloscope bar. The app should drop down. Grab the bottom of the app window and drag it down to the bottom of the screen. Do this for all of the apps you open. It allows you to easily switch between apps while maintaining a large window size. Select 500mV/Div, DC coupling, A1 SE and Enable Channel for channel 1. Select 500mV/Div, DC coupling, and Enable Channel for channel 2.

2 Click on the Mobile Studio Desktop Function Generator Icon. It is just above the Oscilloscope Icon. The function Generator Control panel will show up below the Oscilloscope panel. Go ahead and Auto-Hide this app as you did before. Set the Frequency of Ch 1 to 1.000KHz with 0 Phase and 0V DC offset. Use the Sine waveform and 3.000V Pk-Pk output. Don t worry about Ch2. Enable the Oscilloscope Measurements Window as shown to the right. Set the Measurements to Ch1 and Ch2 to Peak-Peak. Set the Time/Div to 500uS and the Mode to Y-T. Connect the output to a 1.00K resistor. Connect the other end of the resistor to. Connect A1+ to the output at the resistor and A1- to. Click on the scope Start button. If the calibration is set correctly you should see one sine wave on top of the other. With Ch1 and Ch2 equal to 3.00 Vpp. If the calibration isn t correct you should see 2 sine waves in phase with the amplitude of Ch1 different from Ch 2. Re-calibrate if there is a significant voltage difference. 1% accuracy is good enough. Measurement using the Mobile Studio board. You may have noticed the choices for the Ch1 input to the scope were A1 SE, A1 DIF, and AWG2. A brief description of what this means is in order. First and AWG2: select the signal generator outputs using an on board connection. This is an easy way to look at the sig gen output without having to use any wires. The input circuitry to the Mobile Studio board is made up of op-amps and mostly resistors. The configuration of these components is controlled by your selection of A1 SE or A1 DIF. You don t need to adjust any resistances yourself. I will explain what you get when you make a selection. A1 SE means you are going to measure using Ch1 and the measurement will be a single ended measurement. Single ended means the voltage present at A1+ will be measured with respect to. There is an input called A1- and this input can be left unconnected or connected to. The input between A1- and A1+ should be connected to the circuit ground. If you are using the or AWG2 signal source then the is already connected to the signal source on the Mobile Studio Board. In fact all terminals are connected on the board. A1 DIF means you are going to measure using Ch1 and the measurement will be a differential measurement. Differential means that the signal on A1- is subtracted from the signal on A1+. This difference is presented to the input of the scope and measured. The input between A1- and A1+ should be connected to the circuit ground. If you are

3 using the or AWG2 signal source then the is already connected to the signal source on the Mobile Studio Board. Ch2 inputs are the same as Ch1 inputs with the exception that each input signal has a 2 instead of a 1. A2+ and A2-. Math inputs are composed of different combinations of Ch1 and Ch2. You can add, subtract, multiply or divide Ch1 and Ch2 in all combinations. This means you can use math to make a differential measurement. If Ch1 and Ch2 are both SE then the Math function Ch1-Ch2 gives an A1DIF measurement through calculation. It is usually better to measure with A1 DIF compared to (A1 SE A2 SE). 4. Explore the measurement choices. Set the Frequency of Ch 1 of the Function Generator to 1.000KHz with 0 Phase and 0V DC offset. Use the Sine waveform and VPk-Pk output. Build the 2 resistor circuit shown in Fig.1. Calculate the theoretical voltage drop across R1and R2. V R1 V R2 (Vpp) A1+ A1- R1 1.00K VR2 A KHz 3.000Vpp R2 100K A2- Figure 1. Connect the output to R1 and as shown. Connect A1+ and A1- across R1. Connect the between A1+ and A1- to on the breadboard. Set Ch1 to 10mV/Div, DC coupling, A1 DIF and Enable Channel. Connect A2+ and A2- across R2. Note one end of R2 is connected to. Connect the between A2+ and A2- to on the breadboard. Set Ch2 to 500mV/Div, DC coupling, A2 DIF and Enable Channel. Set the Horizontal Time/Div to 500uS. Measure V R1 and V R2. V R1 V R2 (Vpp) 5. Measure the same voltages using 1V/Div: on Ch2. Change the Ch2 Volts/Div. to 1 V. Adjust the Ch1 Volts/Div: to get the large waveform on screen. Don t change Ch2. Measure V R1 and V R2 again. V R1 V R2 (Vpp) Are the observed voltages the same after you changed the Volts/Div: to 1?

4 What happened? Notice the small text message to the right of Ch1 Volts/Div and Ch2 Volts/Div. Ch1 says 10MΩ input resistance and Ch2 says 5990Ω input resistance. Note at 500mV/Div the input resistance of the Mobile Studio hardware is 10MΩ. It falls to 5990Ω when you switch from 500mV to any value greater. 1, 2, 5,10 or 20 Volts/Div. Why do the measured voltages change so much? Use equations. It should take at least several sentences to explain this. (Consider the input impedance of the measurement channel is in parallel with the nodes in the circuit you are measuring). Which set of measurements represent the actual voltages in the circuit? Step 4 Step 5. Why? 6. Measure the voltage V R1 using the MATH function and V R2 using A2 SE. Set Ch1 to 500mV/Div, DC coupling, A1 SE and Enable Channel. Set Ch2 to 500mV/Div, DC coupling, A2 SE and Enable Channel. Move the A1- input wire to. Enable the Math Channel and select Ch1-Ch2. Measure V = V Ch1, V R2 = V Ch2 and V R1 = V MATH. V Ch1, V Ch2, V MATH (Vpp) How well do these measurements, V R1 and V R2, match the measurements from 4 above? Which measurement is less noisy? Which measurement do you trust more? 7. Measure the voltage V R1 using the MATH function and V R2 using A2 SE and 200uS. Set the Horizontal Time/Div to 200uS. Set Ch1 to 500mV/Div, DC coupling, A1 SE and Enable Channel. Set Ch2 to 500mV/Div, DC coupling, A2 SE and Enable Channel. Move the A1- input wire to. Enable the Math Channel and select Ch1-Ch2. Measure V =V Ch1, V R2 =V Ch2 and V R1 =V MATH. V Ch1, V Ch2, V MATH (Vpp) How well do these measurements, V R1 and V R2, match the measurements from 6 above?

5 Comment: It seems that the data based on Math in the measurement window needs at least 5 cycles of the waveform to be accurate. Turn in this document with your answers to the questions and the measured results entered into the provided spots.