Lab #4 The Data Acquisition (DAQ) Card. Read Before Coming to Lab: The Data Acquisition (DAQ) Card (from Appendix A)

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1 The Data Acquisition (DAQ) Card Read Before Coming to Lab: The Data Acquisition (DAQ) Card (from Appendix A) Cards can be inserted into slots in computer mother boards to perform a variety of functions from low speed temperature measurement to high speed digital video capture. There are many data acquisition (DAQ) cards on the market. Here you will use the popular PCI-1200 card manufactured by National Instruments. This card is a PCI device and is useable with any computer with a PCI slot. It was designed primarily for low-cost data acquisition and control. Exercise 0. A First Look The DAQ card, though regarded as an instrument in this course, is different from the standalone instruments you have used thus far in that it is inside your computer and therefore not visible. You will begin by examining what you can see. You will be using a small set of the card s many features so we shall restrict our description to them. Check List Locate the new equipment that was placed at your workstation for this lab. If any of the following items are missing alert your instructor: One UTSC-built breakout box with 50 sockets; the one with the varsity blue cover. A 4 DIN socket adapter for the breakout box A box of components including at least three 10 kω resistors and a number of shorting bars A box with four banana plug tie points for your convenience in wiring circuits A chemical cell mounted on a box for easy connection and an AD595 thermometer with thermocouple. An AC switch and hotplate Banana and coaxial cables hanging up in the lab; you will have to forage for what you need. The Breakout Box The functionality of the DAQ card should be obvious from a study of the breakout box. To get yourself oriented... 1 Identify the 50-conductor ribbon cable emerging from your computer s left rear side. This cable originates from the DAQ card in your computer. The end of the cable nearest you is connected to the breakout box with its 50 numbered sockets. Each conductor in the cable terminates at one of the sockets. This box was designed to make it possible to attach signal sources, devices to be controlled, etc., to the lines of your DAQ. ➁ The pinout of the PCI-1200 connector is reproduced in Figure L4-1. You should be able to relate Figure L4-1 with the box s design in that the sockets are arranged into three parallel groupings. There are analog lines (or channels) colored red and black, digital lines in green and other lines in yellow. 3 You needn t be concerned with all the lines just yet. However, you should be able to identify the 8 analog input lines (ACH0-ACH7), the analog ground (AGND), the two 12-bit DACs with voltage outputs (DAC0OUT, DAC1OUT) and the PA0 and PB0 lines which are, respectively, the single digital input and single digital output lines preconfigured for this lab. We examine these lines in detail in the next section. Configuring the Channels In this lab you will use the four channel types supported by the card: analog input/output and digital input/output. These channels have been preconfigured on your computer by software. Though you don t have to do this yourself, it is useful to understand how the configuration is done. L4-1

2 Analog Lines (red/black) Analog Output Channels The analog output channels (DAC0OUT, DAC1OUT) are configured as single-ended channels with a common ground AGND. Analog outputs thus appear between pins 10 and 11, and between pins 12 and 11. Digital Lines (green) Digital Lines (green) Digital Channels There are 24 digital channels in total. To keep things simple for this course, only 1 digital input channel and 1 digital output channel have been preconfigured on your computer. These are labelled PA0 and PB0 on the pinout, pins 14 and 22, respectively. Pin 13 is their common ground line. Using DAQ Channel Wizard An application called DAQ Channel Wizard is provided by National Instruments for the purpose of simplifying the job of configuring the channels. DAQ Channel Wizard has already been run on the computers in the physics lab. If you wish to see how it works do the following: Other Lines (yellow) Figure L4-1. Pinout of the PCI-1200 DAQ card. The breakout box shows the different lines in parallel groupings and terminating in different colored sockets. 1 Navigate from the desktop through Physics >> PSCB01S >> LabVIEW Demos >> Lab #4 and double-click the alias for DAQ Channel Wizard. The program should run. Wait a few moments for it to search out the configuration and display its findings (Figure L4-2). The 8 input channels can be configured as 8 singleended or as 4 differential inputs according to which input mode is chosen. There are three modes called RSE Input, NRSE Input and Diff Input. You can read about the first two modes in Appendix A. We have made the decision to use Diff mode here so we will concentrate on describing it. Diff Input (Four Channels) Diff input means that each input signal is applied between a signal line and its own special reference line independent of ground. It is the voltage difference between these lines that is measured. Each signal and reference line constitute one input channel. The PCI can monitor 8/2 = 4 such differential analog input signals. In each case, the signal return path is through the input amplifier s inverting ( ) terminal, i.e., through channel 1, 3, 5 or 7, depending on which channel pair is selected. Figure L4-2. DAQ Channel Wizard on bootup shows the configuration prepared on your computer. ➁ When entries appear in the window confirm that the channels have been configured as shown in Figures L4-2 and L4-3. You should see Input Channels numbered 0, 2, 4, and 6, Output L4-2

3 Channels 0 and 1, Digital Input Channel 0 and Digital Output Channel 0. If necessary, you can scroll the window horizontally to get a better view of all entries. If you see anything different alert your instructor. ➂ Channels have a number and a name. Recall that the 8 analog input channels have been paired. Pairs 1 through 4 named AIPair 1, through AIPair 4 are (unhappily) numbered by Lab- VIEW Channels 0, 2, 4 and 6. A Diff channel takes its number from the number of the input signal line of each pair. 4 The 2 analog output channels have been given the names AOOut 1 and AOOut 2. LabVIEW numbers these channels 0 and 1 respectively. 5 The digital input and digital output channels are named DigIn 1 and DigOut 1 respectively. You will see in what follows that sometimes it is more convenient to refer to a channel by name than by number. Lab #4 Figure L4-3. A closeup of a section of DAQ Channel Wizard making the configuration details more visible. 6 If you wish you can click on the Edit button to see a channel s configuration in greater detail (via a dialog box as shown in Figure L4-4). But don t change anything. Figure L4-4. The Edit dialog of DAQ Channel Wizard showing the configuration settings for analog input channel 0, also named AIPair 1. L4-3

4 Notice in the figure that the range for AIPair 1 is 5 volts to +5 volts. This is the default range, meaning that if you leave the controls upper limit and lower limit unwired in your VI, LabVIEW will assume this range (there will be more on the subject of range in the following section). You can change this range as you wish. The scaling is set to No Scaling, so a voltage will be returned exactly as read. AIPair 1 (and AIPair 2 etc) is also set to Differential Mode, as has already been explained. When you have finished studying the configuration, click the Return button and then select Exit to leave DAQ Channel Wizard in the state in which you found it. You are now ready to take your first measurement. Exercise 1. Analog Input The most basic measurement to make with a DAQ card is a single measurement of voltage. With the way your card is configured, you can take four types of analog input measurement: (1) one measurement from one channel, (2) one measurement from multiple channels, (3) multiple measurements from one channel, and (4) multiple measurements from multiple channels. A number of easy DAQ VIs are available for some of these tasks. To keep things simple we shall employ a single sub-vi utilizing intermediate VIs. This sub-vi will then be useable in subsequent activities. This sub-vi is called ReadaScan.vi. Setting Up and Deciphering ReadaScan For your first activity you will take a single measurement of voltage. The most obvious source is your chemical cell. LabVIEW calls this kind of measurement a single-channel, single-point analog input. It is also described as an immediate, non-buffered operation, meaning that the software will read one value from an input channel and immediately return that value to you without buffering or saving it. This operation does not require any buffering or special timing (as might be needed if you wanted to do this repetitively and at high speed). Note from Figure L4-1 that the channel pair named AIPair 1 (Channel 0) terminates in sockets 1 and 2 on the breakout box (labelled ACH0 and ACH1!). Thus you must: maximum of five controls: input limits (no change), device (1), channels (0), buffer size (0) and error in. 1 Plug the box containing your chemical cell into sockets 1 and 2 of the breakout box. Ensure that the positive terminal of the chemical cell goes to socket 1. ➁ Navigate to the folder Lab #4 as you did earlier and load ReadaScan.vi. Its Panel and Diagram are reproduced in Figures L4-5a and b. As can be seen in Figure L4-5b, ReadaScan.vi is built from two intermediate DAQ VIs: AI Config.vi and AI Single Scan.vi. AI Config.vi configures, or sets up, the analog input channels and returns a task ID; it takes a Figure L4-5a. The Panel of ReadaScan.vi. L4-4

5 for channel 0 this is AIPair 1 ). LabVIEW seems to accept only one channel name at a time. (Since you won t be changing them, the controls device (1) and channels (0) could be replaced by constants.) Figure L4-5b. The Diagram of ReadaScan.vi. If you leave input limits unwired, no change is taken by default. The control device (0) is set to 1 by default (your DAQ board is device 1). The control channels (0) is set to 0 by default, which is correct if you have connected your chemical cell to AIPair 1. The control buffer size (0) is set to 0 by default so no buffer is allocated. The code is placed inside a While loop which executes only once each time it is called. A shift register records the task ID on subsequent calls to the VI. The first time it executes, AI Config.vi passes a task ID to AI Single Scan.vi which scans the channels listed in the control channels (0) and returns the voltage values in the indicator voltage read. AI Config.vi is placed inside a Case structure that executes only on a first (zeroth) iteration of the control iteration. This prevents an unnecessary configuration from being performed on subsequent calls to ReadaScan.vi. (To be specific, case 1 and subsequent iterations passes task ID and error in straight through.) As we have stated, ReadaScan.vi is a sub-vi that figures in the actual VI you will use to read the voltage of your chemical cell. If you feel confident you understand how it works then you can ➂ Quit ReadaScan.vi, navigate to the folder Lab #4 and load Read1Pt1Ch.vi. Its Panel and Diagram are reproduced in Figures L4-6. As its name implies this VI is designed to take a single measurement from a single channel. You can spot ReadaScan.vi in the Diagram. The control buffer size (0) is left unwired so no buffer is allocated. Read1Pt1Ch.vi takes a maximum of three controls: input limits (no change), device (1) and channels (0). The control device takes the value 1 as before. As for channels, you have the option of typing in 6, 4, 2 or 0 (or all of them separated by commas) into the control channels (0), or typing in the channel name (recall that Figure L4-6a. The Panel of Read1Pt1Ch.vi. Figure L4-6b. The Diagram of Read1Pt1Ch.vi. With your chemical cell connected to AIPair Run the VI. You should see a measurement number pop into the indicator Voltage Read (Figure L4-6a). Read1Pt1Ch.vi initiated an A/D conversion on the AIPair 1 lines and returned the scaled voltage value as an output. See how quickly you have learned how to turn your computer into a voltmeter! 5 Enter the name AIPair 1 in the control channels (0) and rerun.the VI should work as well as before. Enter your results on the Results Page. L4-5

6 Uncertainty in the Measurement When using a DAQ card you should keep track of the uncertainty in the measurement just as you do when using a DMM. However, the accuracy of the PCI-1200 is described in the NI manual in various ways that might prove confusing. We therefore propose a working accuracy. Since the PCI-1200 is a 12-bit device, it resolves a voltage between the minimum and maximum limits (between 0 and 10 volts for example, or between ±5 volts) to 1 part in 4096, or to about volts. If we add to this number a small contribution in the least significant bit (LSB), say we get a reasonable estimate of accuracy of about ±0.003 volts. This means that the output array indicator should be set to a precision of no more than 3 decimal places. 2 One Measurement from Multiple Channels A single measurement can be taken from a number of channels more-or-less at the same time. This would be necessary if you are studying an effect with four thermocouples, say, one thermocouple connected to its own channel on the DAQ card. Or you might want to carry out the little experiment we shall describe in a moment. Modifying Read1Pt1Ch.vi to read one measurement from the four Diff channels simultaneously is easy to do since we have taken the time to build the sub-vi ReadaScan.vi. Do the following: 1 Quit Read1Pt1Ch.vi and navigate to the folder Lab #4 and load Read1PtMultCh.vi (Figures L4-7). If you compare Figure L4-6b with Figure L4-7b, you should see that the two VIs are almost identical. In the latter the function Index Array has been removed and the array voltages read has been enlarged to show the other array elements, i.e., the measurements from the other channels. The control channels (0) now contains the string 6,4,2,0. Oddly, LabVIEW requires that the channel numbers be entered in decreasing order. This is because the ADC on the PCI-1200 scans downward from the higest-numbered specified channel to the lowest. To run the VI meaningfully you need four voltages to measure. We suggest you set up your chemical cell and three 10 kω resistors on the tie-point box as shown in Figure L4-8. You can run banana cables from the tie points to the four Diff inputs. To make the numbers come out as you expect observe the polarity L4-6 shown. Figure L4-7a. The Panel of Read1PtMultCh.vi. In this case the sum of the voltages at channels 6, 4 and 2 equals the voltage on channel 0. Figure L4-7b. The Diagram of Read1PtMultCh.vi. Chemical cell Channel Channel 2 10 kω 10 kω 10 kω Channel Channel 4 Figure L4-8. A voltage divider circuit. Pin numbers are shown. ➁ Run the VI. You should see four numbers pop into the array voltages read. The first three entries

7 come from channels 6, 4, and 2. The fourth number from Channel 0 is the voltage output from the chemical cell. Thus the sum of the first three numbers should equal the fourth number. Is this true in your case? If you get some negative numbers you probably did not observe the polarities suggested. Enter the results requested on the Results Page. 2 With your chemical cell connected as before, Run the VI. You should see on the screen the measurements of voltage produced at the rate of about 1 each second. With a chemical cell as a source of data you should see a continuous more-or-less horizontal line running across the chart. You can appreciate the fact that if the source were the type to produce a varying voltage then you would end up with a useful time-representation of the effect. Take a few moments to investigate the effect of input limits. The low/high limits are set to 0/2 volt. WARNING: When scanning over all four Diff channels be sure to use a shorting bar on any analog input channel to which a signal is not actually connected. Unpredictable results can sometimes result from scans over unconnected inputs, especially if the lab is electrically noisy. If you are not actually using a channel then just omit it from the control channels (0). 3 Multiple Measurements from One Channel Often one wishes to take measurements repeatedly from a single channel for example, to graph the temperature of a quantity of water or the voltage on a capacitor as a function of time. It is relatively easy to modify our earlier work to do this: 1 Quit Read1PtMultCh.vi and navigate to Lab #4 and load R&GMultPt1Ch.vi (Figures L4-9). R&GMultPt1Ch.vi, as its name implies (?), is designed to read and graph a number of points from one channel. It is in essence a modification of Read1Pt1Ch.vi. A While loop and a stop button have been added to enable measurements from a single channel to be obtained repetitively. The While loop is wired to terminate if the stop button is pressed or if an error occurs. The function Wait Until Next Ms times the spacing between iterations. With the Interval set to 1 the sample rate is approximately 1 Hz. The zeroth element of the returned array is indexed and fed to a waveform chart. Here the controls low limit and high limit are set to 0 volts and 5 volts, respectively, appropriate for the voltage to be expected from your chemical cell. You can change this if you wish. To continue Figure L4-9a. The Panel of R&GMultPt1Ch.vi. Figure L4-9b. The Diagram of R&GMultPt1Ch.vi. L4-7

8 ➂ When you have had enough stop the VI. 4 If you wish to rerun the VI make sure you start with a clean graph. Print the Panel of your VI on the laserwriter printer as proof of your work 4 Multiple Measurements from Multiple Channels In the sciences it is often desireable to obtain multiple measurements from more than one channel. To take an example, in a heat diffusion experiment a bar of material might be fitted with several thermocouples embedded along its length. Heat is then applied to one end of the bar and the thermocouples are read at more-or-less the same time at equal intervals of time. The temperature profile of the material could then be determined. It is just a small step to modify R&GMultPt1Ch.vi to record multiple measurements from multiple channels. A VI has already been prepared for you. Do the following 1 Quit R&GMultPt1Ch.vi and navigate to Lab #4 and load R&GMultPtMultCh.vi (Figures L4-10). This VI is in essence identical to R&GMultPt1Ch.vi, except that the array voltages read has been enlarged to show the measurements from the other channels and the string 6,4,2,0 has been entered into the control channels (0). The function Build Array has been added and the array for Waveform Chart has been transposed. The data from all four channels are plotted on the same graph. The control input limits (no change) has been left as before. The VI, once begun, will stop if the stop button is pressed or if an error occurs in the sub- VI ReadaScan.vi. Figure L4-10a. The Panel of R&GMultPtMultCh.vi. With your chemical cell still connected to AIPair 1 do the following: Figure L4-10b. The Diagram of R&GMultPtMultCh.vi. 1 Run the VI. You should see four measurements in the array voltages read updated at the rate of about one every second and horizontal lines of data drawn on Waveform Chart. ➁ When you have had enough stop the VI. Print the Panel of your VI on the laserwriter printer as proof of your work This concludes our study of VIs for analog input measurements. Feel free to adapt these VIs for use in your term project. We continue in the next exercise with the task of generating a voltage on an analog output channel. L4-8

9 Exercise 2. Analog Output One of the major facts to realize about generating a voltage on an analog output channel is that DAQ cards typically cannot supply a current in excess of about 2 ma. In other words, you cannot use an analog output channel as a supply of power (like the Agilent programmable power supply). Arguably, the most useful application of an analog output channel is to serve as an AC voltage source feeding into a high impedance load outputting an AC signal to a digital oscilloscope for example. Here we consider an example taken from an actual application in the Intermediate Physics Lab, the production of the retarding voltage for a photoelectric apparatus. In this example, the DAQ card is called upon to supply a voltage and only a very small current. Lab #4 1 Outputting a Constant Voltage The first step towards mastering analog output is to produce a constant voltage on a single analog output line. You will generate an output voltage on DAC0 OUT, that is, between sockets 10 and 11. For this purpose we shall take advantage of what LabVIEW calls a Utility VI. To get yourself going do the following: 1 Connect your DMM between sockets 10 and 11. This will enable you to confirm the voltage you output. ➁ Navigate to the folder Lab #4 and load Write1Pt1Ch.vi (Figures L4-11). (0), datum to write, and error in (no error). Figure L4-11b. The Diagram of Write1Pt1Ch.vi. As before, the device number remains at 1 and the control channels at 0. The datum to write you can set anywhere in the range: 5 volts to +5 volts. Two volts will do nicely. To continue ➂ Run the VI. Do you see the output you expect on your DMM? Enter the results requested on the Results Page. 4 Change the datum to write to 0 and rerun the VI. How much time do you reckon the output voltage takes to stabilize? Continue with other data to write until you are satisfied the VI is functioning as intended. 5 Quit the VI and then quit LabVIEW. At this stage what happens to the output voltage? Figure L4-11a. The Panel of Write1Pt1Ch.vi. We now continue in the next activity with outputting voltages repetitively. As can be seen in the Diagram, Write1Pt1Ch.vi is built around the utility VI called AO Write One Update.vi. It takes a maximum of four controls: device (1), channels L4-9

10 2 Outputting a Variable Voltage It is often of gtreat use to be able to output a voltage that can be made to vary over some range. One such case might be to vary the stopping potential for a photoelectric apparatus. It is commonly desireable to vary the voltage uniformly with time. One way of doing this is to enclose the VI of the previous section in a While loop and to wire an array with the values to write from outside the loop. Do the following. Figure L4-12b. The Diagram of WriteMultPt1Ch.vi. 1 Connect your DMM between sockets 10 and 11 if you have removed it after the previous exercise. ➁ Navigate to the folder Lab #4 and load WriteMultPt1Ch.vi (Figures L4-12). You can see from the Diagram that the utility VI is enclosed in a While loop. The four controls are wired from outside the loop (meaning they get read once before the loop is entered). The array data to write is indexed at the While loop boundary. The value indexed is then used to build an array and then passed to AO Write One Update.vi. ( AO Write One Update.vi requires an array input.) Provision has been made to have the While loop terminate when all the elements in the array data to write have been written or when an error occurs. Values get written at the rate of one every 8 seconds, approximately. This interval is set by the function Wait Until Next Ms, and can be changed. To continue ➂ Run the VI. How accurately do the DMM readings reflect the values written? Enter the results requested on the Results Page. Figure L4-12a. The Panel of WriteMultPt1Ch.vi. You may find it useful to output values that do not originate in an array. You can easily modify this VI to include controls to set the minimum and maximum values to write and the increment in the values. This concludes our look at analog output. We continue with digital output in the next exercise. L4-10

11 Exercise 3. Digital Output Digital output is often used in the control of an external device. For example, an output line might be used to provide the logic signal for a signal controlled rectfier to close or open the AC line leading to a device, thereby turning the device on or off. In this exercise we consider this very task. Lab #4 Objective Here you will use the digital output channel DigOut 1 (consisting of the line PB0, or socket 22 and digital ground (DGND, socket 13) to control an AC hotplate. The control will be achieved with an AC switch in the circuit sketched in Figure L4-13. The switch is a signal controlled rectifier or SCR that we have briefly described in Chapter 2. If the PB0 line is HIGH then the AC switch is HIGH or open; if it is LOW, then the switch is closed. In using an AC switch of this nature we need to be certain that the hotplate is not drawing an amount of electrical current that exceeds the current limit of the switch. wired from outside the While loop so they get read only once when the VI begins. port width (8) can be left unchanged. The device number is 1. The channel name is DigOut 1, and the line number is 0, for PB0 or pin 22. Since you will not be changing the first four controls, they could in fact be replaced with constants. AC in PB0 22 DGND AC SWITCH AC out Hotplate 13 Figure L4-13. Circuit used to control an AC hotplate. For the circuit diagram of the AC switch see Figure 3-. Figure L4-14a. The Panel of DigOut.vi. DigOut.vi To get yourself started 1 Complete the connection of the switch to sockets 22 and 13 of your DAQ board as illustrated in Figure L4-13. The hotplate is supplied with the standard AC mains plug which plugs into the AC switch. ➁ Navigate to the folder Lab #4 and load DigOut.vi (Figures L4-14). Figure L4-14b. The Diagram of DigOut.vi. It can be seen from the Diagram that DigOut.vi is built from Write to Digital Line.vi. This VI takes a maximum of five controls: port width (8), device, digital channel, line, and line state. The first four controls mentioned are To continue L4-11

12 ➂ Run the VI and toggle line state to True (or ON). Do you see the red LED next to socket 22 come on? 4 After a few moments place your hand above the hotplate. Is it warming up? 5 Toggle line state ON and OFF. Does the LED respond as expected? 6 When you are confident the VI is working as intended, toggle line state OFF and then quit the VI. A well-written VI would have provision to set line state OFF when the While loop terminates, thus preventing the hotplate from staying on permanently. In fact, LabVIEW does this automatically when it quits. Enter the results requested on the Results Page. We shall now look at digital input. Exercise 4. Digital Input One example of an application using digital input that comes to mind from the Life Sciences is proximity detection. An animal comes to drink at a water bowl and triggers a switch detector. The investigator wishes to record the date and time this happens. We are going to simulate this event with a simple magnetic switch. Magnetic Switch A kind of proximity detector has been prepared for you. This detector is a magnetic switch of a kind that was briefly described in Chapter 6. When the magnet comes into contact with the switch, the switch either opens or closes. The logic of the line can be read via a digital input line (PA0). To examine this VI do the following 1 Complete the connection of the switch to sockets 14 and 13 of your DAQ board. ➁ Navigate to the folder Lab #4 and run DigIn.vi (Figures L4-15). Notice from the Diagram that this VI uses the easy DAQ VI Read from Digital Line.vi. The controls are the same as in DigOut.vi except that the control digital channel here contains the name DigIn 1. Figure L4-15a. The Panel of DigIn.vi. To continue ➂ Run the VI and toggle the switch ON and OFF. When your switch is ON do you see the red LED next to socket 14 come on? Do you see the LED indicator on the VI Panel come on? 4 When you have had enough, quit the VI. Enter the results requested on the Results Page. Figure L4-15b. The Diagram of DigIn.vi. L4-12

13 Exercise 5. Combo Operations The examples we have considered thus far are single concept examples in the sense that they are designed to deal with analog input or analog output, digital input or digital output, but not two or more operations together. But in the real world there are millions of tasks in which combined operations are desired. One example might be to heat a hotplate to bring a quantity of water to a certain temperature, and then to turn the hotplate off when that temperature is reached. We can imagine that the digital output line is used to turn an AC switch ON or OFF through which the hotplate is connected. An analog input line is used to measure the output from a thermocouple or equivalent temperature sensor placed in the water. The VI starts by closing the AC switch. The temperature is then read continuously until it reaches a certain value, at which time the digital output line switches the AC line OFF. Lab #4 AnIn&DigOut.vi A VI to perform the functions just described has been prepared as an example. Do the following 1 Navigate to the folder Lab #4 and load AnIn& DigOut.vi (Figures L4-16). This VI combines the VIs R&GMultPt1Ch.vi and Dig Out.vi. This VI was run with the AD595 temperature sensor (Chapter 6) connected to Diff input 0 so the multiplication or Cal factor was set at 100. The toggle control toggles the digital output line ON or OFF. Delay refers to the time, in seconds, between updates. Other features of the Panel should be familiar enough to you not to warrant much comment. We shall concentrate our attention here on the Diagram. Figure L4-16a. The Panel of AnIn&DigOut.vi shown after about 20 minutes running time heating the AC oven. You should be able to spot on the Diagram the Digital Output Area and the Analog Input Area. The same iteration counter is wired to Write to Digital Line.vi and to ReadaScan.vi. The inputs to Write to Digital Line.vi which were controls in previous VIs have been replaced here with constants. L4-13

14 To continue... ➁ Setup a quantity of water in a beaker on the hotplate. ➂ Plug your AD595 sensor into Diff input 0 on the DAQ braekout box and run the thermocouple to water in the beaker. 4 The AD595 device needs to be powered so run a banana cable from the (+) red socket on the device to the +5 volts (socket 49) on the box. Run a banana cable from the black (GND) socket on the device to AGND (socket 11) on the box. 5 Run the VI. Toggle the output line ON. After a few minutes do you observe the temperature increasing? Notice that the VI employs a waveform chart. This means that the data gets plotted on the chart one point at a time. When the plot reaches the right-hand edge of the chart, the chart scrolls. 6 When your chart begins to scroll, stop the VI. It should resemble Figure L4-16a. Print the Panel of your VI on the laserwriter printer as proof of your work Figure L4-16b. The Diagram of AnIn&DigOut.vi. L4-14

15 Exercise 6. Using Vernier Sensors with the DAQ Card Chapter 6 was devoted to descriptions of a large number of sensors, many of which are produced by Vernier Software. In this exercise, which is a return to analog input, we examine in detail how Vernier Software sensors can be used with the DAQ card. Of course, any sensor that produces an analog output can be used with the card. We concentrate here on Vernier Software sensors only because we have an ample supply of them. Lab #4 The Four Sensor Adapter An adapter is provided to enable you to use up to 4 Vernier Software sensors with your DAQ card. Locate this adapter at your workstation and plug it into the four analog input sockets. The adapter has red and black banana sockets for the supply of the power the sensors require. Connect the red socket to the +5V socket on the breakout box (socket 49) and the black (ground) socket to analog ground (socket 11). L4-15

16 Results Page Name: Student #: Exercise 1 Analog Input measured voltage 1 Read1Pt1Ch.vi 2 Read1PtMultCh.vi 1 st voltage read 2 nd voltage read 3 rd voltage read 4 th voltage read sum of voltages R&GMultPt1Ch.vi Printout of Panel 4 R&GMultPtMultCh.vi Printout of Panel Exercise 2. Analog Output Voltage specified in datum to write Voltage Measured on DMM 1 Write1Pt1Ch.vi Typical Voltage specified in datum to write Voltage Measured on DMM 2 WriteMultPt1Ch.vi L4-16

17 Exercise 3. Digital Output Lab #4 LEDs indicate as expected? Y/N Hotplate warmed up? Y/N DigOut.vi LEDs indicate as expected? Y/N Exercise 4. Digital Input Digin.vi Exercise 5. Combo Operations Anin&DigOut.vi Printout of Panel Exercise 6. Using Vernier Sensors with a DAQ Card L4-17