Documentation for the Preferences Command on the Edit Menu in WinDaq/Pro and WinDaq/Pro+ Software

Selecting Preferences from the Edit menu displays a submenu of rarely-changed configuration items. When selected, these items allow you to adjust WinDaq/Pro or WinDaq/Pro+ configuration parameters such as update interval, scroll limit, skip factor, buffer size, beep on gap, frame rate, maximum sample rate, event mark capacity, open new file on full, record next file on full, and thermocouple type to better suit your computer's hardware or otherwise influence performance. Each preference item is described as follows:

Update Interval
Scroll Limit
Skip Factor
Buffer Size
Beep on Gap
Frame Rate
Maximum Sample Rate
Event Mark Capacity
Open New File on Full
Next File on Full
Thermocouple Type

UPDATE INTERVAL - Allows you to specify the minimum time (in milliseconds) between screen updates. By setting a minimum time interval between screen updates, you prevent WinDaq/Pro or WinDaq/Pro+ from using too much CPU time at the expense of other tasks.

Note that this preference item is simply a "graphics adjuster" that only affects how the display looks on your computer's screen. Data acquired to disk is independent of this function.

Valid update interval entries range from 0 to 32,767. The default interval is 0. At an interval of 0 (no time between screen updates) the display is optimized, it will update as fast as your display controller hardware will allow. However at this setting, WinDaq/Pro or WinDaq/Pro+ burdens the CPU with constant screen update requests. The CPU spends most of its time providing this optimized display, thus leaving little time to process other tasks. At an interval of 32,767 (approximately 33 seconds between screen updates) the display is at the opposite end of the performance spectrum, updating very slowly. Because of these infrequent screen update requests, the CPU has a lot of free time to handle other tasks, but as you can imagine, the term ' real time display' becomes a misnomer.

With this preference item, you can trade display performance for system time availability (experimentation is encouraged). Decide which is more important; visually pleasing display performance or multitasking capability, and adjust the update interval accordingly.

SCROLL LIMIT - Allows you to specify the maximum width (in pixels) of discontinuity from the right edge of the screen. If you do not see any discontinuity in the display, the scroll limit is adjusted properly for your computer and your typical operating conditions. If you do see some display discontinuity, you can adjust the scroll limit to compensate for the discontinuity and improve the appearance of your display.

It should be noted that this preference item is simply a "graphics adjuster" that only affects how the display looks on your screen. Data acquired to disk is independent of this function.

Valid scroll limit entries range from 0 to 32,767. The default limit is 0. In most cases, the scroll limit should be set to zero and left there. At a scroll limit of 0, no discontinuity will exist. In other cases where special hardware has been installed in your computer to accelerate display performance, the scroll limit should be maximized to take advantage of your display adapters enhanced capability. In the rest of the cases, the scroll limit can be experimented with to provide the best looking display.

If you have a computer with a slower processor and a standard VGA display adapter (or less), the scroll limit should be set to 0. On this type of personal computer, there is nothing to gain by increasing the scroll limit. If you wish to enhance the appearance or performance of your display, try other methods such as increasing compression, decreasing the window size, decreasing the sample rate, or selecting the Fast Scroll option from the Options menu.

If you have a computer equipped with a co-processor based display adapter that is capable of scrolling (such as the IBM 8514 PS2, any XGA controller, or any Windows graphics accelerator), the scroll limit should be set to 32,767. On this type of personal computer, the display discontinuity can be eliminated or minimized and the display performance can be optimized by maximizing the scroll limit.

If neither of the above applies, or if you really want to tweak your real time display, you can experiment with the scroll limit to find the most visually pleasing display. Start with a scroll limit of 2 and keep doubling it (up to the horizontal resolution of your monitor) until the display appears and performs satisfactorily. While it causes no harm, there is nothing to gain by setting the scroll limit higher than the horizontal resolution of your monitor.

SKIP FACTOR (Nonfunctional When Used With Serial Port Instruments) - Allows you to specify the ratio of the total number of data points to the number used for screen display at the maximum sample rate. For example, specifying a skip factor of 20 means that for every 20 acquired data points, only 1 will be used for screen display purposes (ratio of 20:1). Similarly, a skip factor of 1 means every data point acquired will be used for screen display purposes (a 1:1 relationship).

It should be noted that this preference item is simply a "graphics adjuster" that only affects how the display looks and performs on your screen. Data acquired to disk is independent of this function.

Real time display performance degrades when attempting to plot too many data points in a given period of time. Specifying a skip factor improves real time display performance by lessening the plotting workload. With a skip factor, you improve display performance by instructing WinDaq/Pro or WinDaq/Pro+ to plot every nth data point and ignore the rest of the incoming data. However since the rest of the data is ignored, the result is a potentially inaccurate screen representation of the acquired data. Therefore, the skip factor should be considered a last resort for improving display performance if screen accuracy of the waveform data is desired.

Valid entries range from 1 to 100. At a factor of 1 (no sample skipping) the screen display is the most accurate, detailed representation of the acquired data. However at this setting, the CPU is burdened with constant plotting operations. At a factor of 100 (plot every 100th data point on the screen and ignore the rest), CPU operations for the real time display are minimal (the workload is lightened) but the displayed waveform is at best only a compromised representation of the acquired data.

BUFFER SIZE (Nonfunctional When Used With Serial Port Instruments) - Allows you to specify the size of input buffer needed for gap-free data recording at the maximum sample rate. By setting the buffer size, you can specify the correct amount of memory needed for acquiring data gap-free at your computer's maximum sample rate while allowing you to simultaneously run your other usual applications.

The input buffer is where the acquired data is temporarily stored before it gets written to your hard disk. If the ratio of sample rate to buffer size is too small, the sample rate in the status bar is shown in reverse video. This is a warning that you may not be able to reliably store data to disk (some data points may be skipped or lost, therefore creating gaps in the data stream going to disk). To find the correct input buffer size, refer to the Streaming Data to Disk flow chart in Appendix A of the WinDaq/Pro or WinDaq/Pro+ User's Manual.

The current size of this buffer can be seen in the Edit Sample Rate dialog box.

The amount of buffer space allocated is automatic, is proportional to the sample rate, and generally is not in need of manual adjustment. Manual allocation of buffer size is generally only needed when the sample rate is displayed in reverse video (refer to Appendix A), when multitasking with many applications, or when you wish to allocate a large input buffer at a low sample rate (to accommodate slow computers).

BEEP ON GAP - Allows you to enable/disable a short audible beep that sounds when your computer is too busy with other tasks to store gap-free data. When the beep on gap option is enabled, a check mark is displayed on the Edit Preferences submenu immediately preceding the Beep on Gap command.

FRAME RATE - Allows you to enable/disable the display of screen updates (in frames/sec). When enabled, the number of screen updates per second (how many times per second the display is redrawn or updated) is displayed in the right end of the status bar. When the frame rate option is enabled, a check mark is displayed on the Edit Preferences submenu immediately preceding the Frame Rate command.

MAXIMUM SAMPLE RATE (Nonfunctional When Used With Serial Port Instruments) - Allows you to set the maximum burst rate, which ultimately determines the sample rate. All Dataq Instruments hardware products continuously sample data using a burst sampling technique. The hardware samples data at one rate (referred to as the burst rate) while your computer reports (i.e., displays and stores) this data at another rate (called the sample rate or throughput rate). On some computers, a burst rate near 80 kHz can result in channel swapping (i.e., the data from one channel is displayed on a different channel) on the screen and in the data file when DOS programs are run simultaneously with WinDaq/Pro or WinDaq/Pro+. On other computers, a burst rate near 80 kHz can even halt the system with a memory parity error. Values above 40 kHz are not recommended for the DI-220 or when using thermocouple inputs. The actual DMA burst rate will be greater than half the maximum sample rate, with averaging applied at sample rates less than or equal to half the maximum.

It is to your advantage to set the maximum sample rate as high as it will go without experiencing channel swapping or memory parity errors, while simultaneously limiting it to "convenient" values (i.e., 40 kHz or 50 kHz rather than 47 kHz or 52 kHz). A "convenient" value will provide a larger number of sample rate submultiples.

As a general rule, use the following chart to determine the max:

Models Maximum Sample Rate
DI-710, DI-715B, DI-718B, DI-718Bx 4.8kHz
DI-148, DI-158 14.4kHz
DI-220, DI-221TC 40kHz
DI-200, DI-210, DI-722, DI-720-E (Rev A), DI-730-E (Rev A) 50kHz
DI-720-E (Rev B), DI-730 (all others) 150kHz
DI-720-USB 200kHz
DI-400, DI-500, DI-720-PP 250kHz

This menu item is disabled when used with a serial port instrument connected directly to a COM port.

EVENT MARK CAPACITY - Allows you to set the maximum number of event mark entries available for a given data acquisition session (from when recording is selected to when stop is selected). If a large number of event mark entries are made, setting the capacity higher will make more memory available to WinDaq/Pro or WinDaq/Pro+ for the next start up.

Valid entries range from 1024 to 16,384. The default value of 1024 is generally sufficient for most users. Each event marker and each comment require one entry apiece, while two entries are required each time acquisition is started (either manually or remotely).

OPEN NEW FILE ON FULL - Enables/disables the ability to close a full file and display the dialog box required to open another new file. For example, say you are acquiring data and the file becomes full much sooner than you anticipated, yet you still need more data. If this preference is disabled, you would have to close this full file and then select the Open command from the File menu to name and open a new file to continue the acquisition session. However if this preference is enabled, you bypass the need to close the full file and select File Open. The File Open dialog box is automatically displayed for you, conveniently allowing you to enter a new file name.

If this preference is enabled and if the old or full filename (excluding file extension) consists of just alpha characters (e.g., WEASEL.WDQ), the File Name text box of the Open dialog box is highlighted, enabling you to immediately enter a new file name.

If the old filename (excluding extension) ended in numeric digits (e.g., WEASEL1.WDQ), the numeric portion is automatically incremented (e.g., WEASEL2.WDQ) and highlighted in the File Name text box of the Open dialog box suggesting the default new name. This feature allows you to acquire data to a series of sequentially-named files. If the numeric suffix of the old name is all nines (e.g., WEAS9999.WDQ), no specific next name is suggested.

When enabled, a check mark is displayed on the Edit Preferences submenu immediately preceding the Open New File on Full command.

NEXT FILE ON FULL - Enables/disables the ability to automatically close a full file, enter a new file name, and start recording another new file. For example, say you are acquiring data and the file becomes full much sooner than you anticipated, yet you still need more data. If this preference is disabled, you would have to close this full file and then select the Open command from the File menu to name and open a new file, thus continuing the acquisition session but losing data while doing all of the file manipulating. If this preference is enabled, the last character of the old filename is automatically incremented when full and recording is started automatically to this new filename. If this new file is allowed to become full, the last character of this new filename is decremented (effectively getting you back to the file you started with) and recording automatically continues (thus overwriting the old data file). Recording continues alternately between this pair of files until it is stopped by the user.

For example suppose this preference is enabled, you are acquiring data to a file called RAT.WDQ, and it is approaching full size. When full, recording will automatically continue but to a different file called RAU.WDQ. Similarly, when RAU.WDQ reaches full size, recording will automatically continue but back to file RAT.WDQ.

The last character of the filename (excluding the file extension, if any) is the character that is incremented/decremented.

If a file with the new name already exists, the file is automatically deleted before the new one is opened.

There is a discontinuity between the data at the end of one file and the start of the next, but it is short if your computer system is not busy with other tasks such as reading disk drives or printing.

If the Open New File on Full preference is also selected and the old filename (excluding extension) ended in numeric digits (e.g., WEASEL1.WDQ), the numeric portion is automatically incremented (e.g., WEASEL2.WDQ). If the numeric suffix of the old name is all nines (e.g., WEAS9999.WDQ), the new name will wrap back to all zeroes without incrementing the preceding character (e.g., WEAS0000.WDQ).

When enabled, a check mark is displayed on the Edit Preferences submenu immediately preceding the Record Next File on Full command.

THERMOCOUPLE TYPE (DI-221TC Only. Nonfunctional When Used With Serial Port Instruments) - Allows you to select the type of linearization that will be applied to all thermocouple channels (as set up in the Edit Channel Settings dialog box). For example, if you have four channels that are set up as thermocouple channels, selecting type "K" linearization with this preference applies it to all four thermocouple channels. It is not possible to apply type "J" linearization to one channel, type "K" linearization to another, and type "T" linearization to the other two.

Valid linearization selections are type J, K, R, and T.