National Instruments Analog-to-Digital (NI A2D) Module Manual

Transcription

1 Particle Analysis and Display System (PADS): National Instruments Analog-to-Digital (NI A2D) Module Manual DOC-0292 Rev A PADS 3.5, NI A2D Module Central Avenue Boulder, CO USA C O P Y R I G H T D R O P L E T M E A S U R E M E N T T E C H N O L O G I E S, I N C

2 Copyright 2011 Droplet Measurement Technologies, Inc CENTRAL AVENUE BOULDER, COLORADO, USA TEL: +1 (303) FAX: +1 (303) All rights reserved. DMT licenses PADS software only upon the condition that you accept all of the terms contained in this license agreement. Each PADS license you purchase allows you to acquire data on one computer only. Data can be viewed in playback mode on an unlimited number of computers. This software is provided by DMT as is and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. Under no circumstances and under no legal theory, whether in tort, contract, or otherwise, shall DMT or its developers be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including damages for work stoppage; computer failure or malfunction; loss of goodwill; loss of use, data or profits; or for any and all other damages and losses). Some states do not allow the limitation or exclusion of implied warranties and you may be entitled to additional rights in those states. Trademark Information All Droplet Measurement Technologies, Inc. product names and the Droplet Measurement Technologies, Inc. logo are trademarks of Droplet Measurement Technologies, Inc. All other brands and product names are trademarks of their respective owners. Risks of Installing Additional Software Instrument computers from DMT are configured to acquire data in a reliable, robust manner. Typically, such instruments are either not connected to a network or are connected to a small, local network that is isolated from the internet, reducing the risk of viruses. Since anti-virus programs can cause erratic behavior when run in the background on data acquisition computers, DMT does not install anti-virus, anti-spam, or anti-malware programs. If you choose to install these programs, you accept the risk associated with them in terms of potential performance degradation of the software installed by DMT. For similar reasons, DMT recommends that you do not install or run other software on the dedicated instrument computer. Although the installation of some software may be unavoidable, it is particularly important not to run other software while the computer is acquiring data. DOC-0292 Rev A II

3 C O N T E N T S 1.0 Introduction Requirements Configuration Configuring the NI A2D NI A2D Param. Box Shared Settings Box Manual Channels Channels Table Configuring the NI A2D Display The NI A2D Window NI A2D Plots and Numeric Displays Tab NI A2D Channels Tab Appendix A: NI A2D Channels Appendix B: Revisions to Manual L i s t o f F i g u r e s Figure 1: NI A2D Configuration Editor Window... 5 Figure 2: National Instruments Measurement and Automation Explorer... 6 Figure 3: Example Channel Specifications in the NI A2D Config Editor Window 9 Figure 4: NI A2D Display Editor Window Figure 5: NI A2D Window DOC-0292 Rev A I I I

4 1.0 Introduction The Particle Analysis and Display System (PADS) is a software package that interfaces with instruments produced by Droplet Measurement Technologies (DMT) and other leading instruments used in the atmospheric sciences. This manual describes the PADS National Instruments Analog-to-Digital hardware (NI A2D) module version For an explanation of the basic PADS setup and instructions on how to acquire data using PADS, consult the PADS Overview Manual, DOC Definitions and calculations used in the NI A2D module are also described in the PADS Overview Manual. The section below describes the requirements for making your NI device interface with PADS. The next sections describe how to configure your NI A2D and the NI A2D display in PADS. 1.1 Requirements The PADS NI A2D module will work with most National Instruments data acquisition devices, including E-Series plug-in boards, M-Series plug-in boards, and USB devices such as USB However, PADS does not support older NI devices with traditional NI-DAQ software drivers. Devices must use NI-DAQmx drivers. Each NI device requires its own PADS tab. 2.0 Configuration 2.1 Configuring the NI A2D Before configuring your NI A2D device in PADS, you may want to test that the device is working properly by itself. You can find many useful diagnostics for testing your device in the National Instruments Measurement and Automation Explorer (MAX). To get to the Explorer, select Start > Programs > National Instruments > Measurement & Automation. See National Instruments documentation for instructions on using MAX. To configure the NI device from within PADS, follow the steps below. DOC-0292 Rev A 4

5 1. Click on the NI A2D tab. 2. From the Configure menu, select Configure Instrument. You will see the following window. Figure 1: NI A2D Configuration Editor Window 3. Now you can configure the instrument parameters to your desired specifications. You will find definitions of these parameters below. If at any time you would like to revert to the previously saved values for the NI A2D parameters, press Cancel to exit the window without saving changes. 4. When you are done configuring the NI A2D parameters, press Save at the top of the Config editor window. (If you would instead like to revert to the previously saved values, click Cancel.) Then press the green Reset Program button for the new configuration to take effect. Note that pressing the Reset Program button will clear any data currently being displayed. DOC-0292 Rev A 5

6 The NI A2D configuration editor screen allows you to specify the parameters listed below. Instrument #: This lists the number corresponding to the instrument you are viewing, in this case the NI A2D. If your NI A2D has been assigned instrument number one, you will see 1 in this field. You should not need to modify the instrument number, and in fact you are unable to do so from within PADS NI A2D Param. Box The NI Device # indicates the National Instruments device number. If you have multiple NI devices, this number helps PADS distinguish inputs from the different devices. You must have a separate PADS tab for each NI Device. If you do not know the NI device number, you can find it by going to Start > Programs > National Instruments > Measurement & Automation. This will bring up the screen shown in Figure 2. In the left window, go to My System > Devices and Interfaces. (If you cannot see these headings, click on the + signs to expand subheadings as necessary.) Your device and the device number should be listed. In Figure 2, for instance, the NI device is a USB-6008 and the device number is 2. The device number listed here must match that listed on the NI A2D Configuration Editor screen. Figure 2: National Instruments Measurement and Automation Explorer DOC-0292 Rev A 6

7 NI-DAQmx is the software driver that the device uses. Note that PADS can only support NI A2D devices that use NI-DAQmx drivers. Devices that are listed under Traditional NI- DAQ are not supported. At Startup Enabled / Disabled: If you want the NI A2D to acquire data when PADS begins sampling, make sure this parameter is in the Enabled mode. In some cases, such as if the NI A2D is inoperative, you may want to use this control to disable the probe. Disabling the NI A2D allows data to transmit from other instruments without interference. Data will still be written to the disabled instrument s output file, but PADS will write NaN to all fields. Differential / Single-Ended Switch: This control tells PADS whether the NI-DAQ device will be used in single-ended mode or differential mode. PADS expects all output channels to be in the same category; you cannot have some channels with a single-ended setup and others with a differential setup. A differential wiring scheme will yield only half the number of input channels of a single-ended setup, but readings may be more accurate. For more information, consult the NI device s hardware manual. Samples per Period: This is the number of samples the NI A2D will take during the time interval specified by Sample Time. For instance, if you have Sample Time set to 1 second, and Samples per Period set to 2,000, the NI A2D will sample 2,000 times per second. If you set Sample Time to 2 sec and Samples per Period to 4,000, the NI A2D will still sample 2,000 times per second, but data will only get relayed to the computer once every two seconds. Sample Time: This parameter shows the time interval you'd like between samples. You can have the probe sample at intervals between 0.04 and 20 sec (25 to 0.05 Hz). Note: Sample Time is most often set to 1 Sec. Higher sample rates may or may not work on a given data system, depending on the capabilities of the NI hardware being used. GPS Source: This control allows the user to specify the source for GPS time, if one is available. If no GPS sources are available, this control will not appear Shared Settings Box On the right side of the Config Editor screen are controls that allow the user to specify if the NI A2D device measures the shared variables Probe Air Speed (PAS), pressure, temperature, and hotwire voltages. Clicking the Available button indicates that the NI DOC-0292 Rev A 7

8 A2D device is acquiring the variable in question, while the Channel control specifies which channel number will is acquiring this data. Setting these controls properly insures that if the NI A2D device is providing these variables, other instruments will be able to specify the device as a source. Thus the CDP, for instance, could use the NI A2D s temperature reading as its own temperature. Note that if a Hotwire voltage channel is specified, a HW Slave channel must also be specified. Note that specifying channels using the Shared Settings controls does not, by itself, cause these channels to be written to the output file. They must also be entered in the Channels Table, along with any necessary numeric values Manual Channels The boxed Manual Channels control allows users to designate manual channels that will be included in the NI A2D device s output data file. These channels will not be read in from the device, but rather will store the data entered manually by the operator. These manual values can be changed by the operator on the NI A2D Channels tab, and their initial values are those listed in the Value field of the configuration screen. For instance, if you wanted to record a flying altitude of 15,000 feet, you could define a manual channel named Altitude (ft) and set the Value to (Figure 1). In the output file, manual channels appear after channels read from the NI A2D device Channels Table The bottom half of the NI A2D Config Editor screen lists the configurable channel information, as shown in Figures 1 and 3. You can use the channels table to add and delete channels from the instrument. Every channel listed in the Config Editor screen will be listed in the instrument s output file. The raw values returned by the instrument s channels can be turned into other, more meaningful units (e.g., mbar or C) by using a conversion equation. You can specify this equation in the channels table. The channels table allows you to set the parameters listed below. Note: All channels MUST be listed in the channels table for them to appear in the output file. Simply clicking on PAS Available, for instance, will not result in meaningful PAS values being written to the output file. If no channels are currently listed in the table, you must click on a button in the Insert column before you can specify channel parameters. Clicking on a button in the Delete column deletes the channel listed in that row. DOC-0292 Rev A 8

9 Channel Name: The first column in the table specifies the channel s name as it will appear in PADS and in the data file. Scaling: The second column in the table indicates the type of equation that PADS should use linear, polynomial, or none. ( Thermister D and Thermister G are complicated, preset equations used by some instruments, while the Custom options are reserved for future use. You should not need to select these options.) Linear indicates a linear equation, while 4 th Order Poly indicates a higher order polynomial equation with up to five terms. None means the measured voltage will be returned without any scaling. Scaling Coefficients: The columns marked 0 th through 4 th Order in the channels table indicate the coefficients to be used in the conversion equation. Figure 3 shows the setup for a hypothetical channel with a linear conversion equation, as follows: 1 TC0 = x where x is the digitized analog value returned by the A/D converter. Figure 3: Example Channel Specifications in the NI A2D Config Editor Window The number of coefficients that PADS uses depends on the equation type. None does not use any coefficients. Linear uses the coefficients listed in the columns marked 0 th and 1 st order. 4 th Order Poly can use any of the coefficients listed in the columns marked 0 th 4 th order. In cases where there are non-zero numbers in cells that are not used in the function, PADS ignores these numbers. For instance, if you specify Linear as your function and have.32 in the 4 th order column, the program will just ignore this value. Chan. Number: This field indicates the input channel on the NI A2D device. The number on the NI hardware must correspond to the number specified in PADS. For more information on which channels correspond to which connection pins, consult the NI device s hardware manual or the Measurement and Automation Explorer. Range: This field indicates the minimum and maximum voltage inputs for the NI A2D device. These values will depend on the sensor that is feeding the device data. For the range 1 This channel is for a temperature (ºC) reading. However, it is quite unusual to be able to scale a temperature sensor s reading linearly, as in this example. In this case extra hardware was added to the original temperature sensor in order to make the output linear. DOC-0292 Rev A 9

10 parameter in PADS, you want to select the values that most closely match the voltage range of the sensor. Choosing a significantly larger range will lower the data resolution. You also want to make sure the range listed in the Range field completely encompasses the actual spectrum of data, however, since otherwise data can be lost. (Note that NI device s range should also encompass that of the sensor, or otherwise the device itself may lose data before it ever gets relayed to PADS.) Finally, note that not all NI devices support all the listed ranges. Consult the NI device hardware manual for more information. In general, if a Range is selected that is not supported by the device, the device will acquire data using the next largest available range. For best results, however, Range should be set to values that are valid for the NI device being used. Pressing Reset Parameters resets all configuration parameters to their default values. Pressing Reset Default Channels resets all the channels in the Channels table to their default values. After making changes in the instrument configuration window, you will need to press the Save button and then click the green Reset Program to activate these changes. Note that clicking Reset Program will clear any data PADS is currently displaying. 2.2 Configuring the NI A2D Display To configure the NI A2D display, click on the NI A2D tab if you have not already done so. Then select Configure from the menu bar and click on Configure Display. This will bring up the following window. DOC-0292 Rev A 10

11 Figure 4: NI A2D Display Editor Window Display # or Instrument # cannot be modified. Changing the Refresh Time allows you to set the time intervals for data display during acquisition mode; you can choose any time that is equal to or greater than the sample time. (Choosing a time less than the sample time is not useful, since the same data will be displayed multiple times.) The four graph fields at the bottom of the NI A2D Display Parameter box allow you to configure the channels on the NI A2D s two graphs. You can click on the arrow buttons to scroll between available options for the channels. You can also click on the white fields to bring up a list of all the available options, from which you can then choose the channel you want. When you are done, click on Save to update the configurations or Cancel to revert to the previous configurations. After you reset PADS, you will be able to see any changes on the NI A2D tab. Note that clicking Reset Program will clear out any data currently being displayed. DOC-0292 Rev A 11

12 Configuring channels in the Configuration Display Editor will change the display upon start-up. Once PADS has started, you can select any channels to be displayed from the NI A2D window itself. 3.0 The NI A2D Window The top right of the NI A2D Window displays the NI Device #, the Enabled/Disabled button, the Fault/No Fault button, and the NI A2D PADS module version number. For a definition of the NI Device # channel, see section 2.1. For explanations of the Enabled button and the Fault/No Fault button, see the Instrument Tabs section of the PADS Overview Manual. 3.1 NI A2D Plots and Numeric Displays Tab The NI A2D Plots and Numeric Displays sub-tab consists of two graphs that display two channels each. These channels are always graphed with respect to time, as in shown in Figure 5. PADS displays the channels listed in the graph s left-hand fields in green. The y- axis legends for these channels are listed on the far left side of the graphs. It displays right-hand fields in blue, and it lists these legends on the far right of the graphs. DOC-0292 Rev A 12

13 Figure 5: NI A2D Window To change the channels plotted in the charts, you have two options: 1.) To change the charts for the current session only, use the controls in the upper corners of the charts to select the channel you desire. You can either click on the text control to the right, which brings up a selectable list of channels, or you can use the button on the left to scroll between channels. 2.) To change the channels shown in the chart s display when PADS starts, go to the Configure menu, select Configure Display, and choose the desired channels. Then press the Reset Changes button to apply this configuration. When you view charts in playback mode, the currently selected moment in time is indicated by a red cursor. The y-axis value for this time is indicated by cross (+) on this cursor. Y-axis values marked with the cursor are always for channels displayed in green. Note that when you display a large range of time-series data, the chart display does not have sufficient resolution to display each individual time point. To increase resolution, zoom in on the data by changing the time interval to a smaller range. On all the charts with x and y axes, you can change the scale by typing a different number into the starting and ending values on each axis. For instance, if you want to DOC-0292 Rev A 13

14 change the time period in one of the graphs above to end at 10:54:00, you simply select the field that currently says 10:54:33, type in 10:54:00, and hit the <Enter> key. In acquisition mode, you must disable autoscaling (see below) before you modify fields in this way. Many charts also show you options for scaling and copying the data when you right-click on them, which brings up a drop-down menu. These options are as follows: Autoscale This autoscales the relevant axis. In autoscaling mode, the minimum and maximum values of the axis are set automatically so that all data points can be seen in the display. Note that on charts that have autoscale buttons, like the large histogram chart on some instrument tabs, the buttons override the Autoscale options in the drop-down menu. To see autoscaling options in the drop-down menu, position the cursor over the relevant axis before right-clicking. Note that you may not always be able to autoscale the x-axis. Copy Data This copies the chart to the clipboard using a screen capture. This chart can then be pasted into other documents like Word or PowerPoint presentations. Export Simplified Image This copies a simplified image of the data to the clipboard or an output file. You can choose the format you desire bitmap (.bmp), encapsulated postscript (.eps), or enhanced metafile (.emf). Note that when you select the.eps option, you must copy the data to a file. Unless you specify otherwise, output files will be saved in the time-and-date-specific output file directory for the current session. Clear Graph This erases the currently displayed data points from the graph. 3.2 NI A2D Channels Tab The NI A2D Channels tab lists tabular data for the current moment in time. The top portion of the display lists the scaled channels values (far right) along with their scaling coefficients. The scaling coefficients correspond to those specified in the Config Editor screen. The bottom section of the window lists the manual channels and their corresponding values. These can be changed during sampling by simply entering new values into the Manual Channel Value fields. Such modifications will be valid for the current session only; to change the manual channels that are used on program start-up, use the Config Editor (Configure > Configure Instrument). DOC-0292 Rev A 14

15 Appendix A: NI A2D Channels NI A2D has five default channels: End Seconds Day of Year Year Status GPS/UTC Seconds Two additional channels, Date and Time, may be listed before GPS Time/ UTC Seconds if Write Date & Time Stamp is enabled on the Setup tab. GPS Time is reported if there is an instrument on the system that reports GPS Time; otherwise, this channel is UTC Seconds. End Seconds, Day of Year, Year and GPS/UTC Seconds are time channels. Status stores statistical data the NI A2D has gathered on the communication between PADS and the NI device; 1 indicates good communication. The output file may contain a fifth channel, GPS Time, if the system also has a GPS. This channel may be measured by an instrument other than the NI A2D. The output file will also list any channels that you have specified in the NI A2D Config Editor s screen. For these configurable channels and the default channels listed above, the output file will contain data values for each sampling instance. You can also plot each of these channels with respect to time on the NI A2D window. For definitions of the default channels, see Appendix A in the PADS Overview Manual, DOC-300. Appendix B: Revisions to Manual This document replaces DOC-0195, the NI A2D PADS Operator Manual for PADS version 2.X. DOC-0292 Rev A 15