Sample Rate > Activating Procedure

Activating Procedure

Click the Sample Rate button in the Toolbox.

In the Edit menu click on Sample Rate….

Double-click on the S/s (F3): field in the status bar.

Choose Edit Sample Rate… (ALT, E, R).

Press F3.

The sample rate dialog box opens.

Setting Sample Rate for all other instruments

It is here that a specific sample rate may be configured.Enter the desired throughput rate (or total scanning rate) in the Sample Rate text box in samples per second. For example, if you wanted to acquire two channels of data both at 40 Hz, you would enter a throughput rate of 80 in the text box.

If you are using WinDaq/Pro+, you have the ability to sample different channels at different rates. Because of this feature, the sample throughput rate (total scanning rate) is calculated differently. To calculate a total sample throughput rate for WinDaq/Pro+, multiply the number of channels to be recorded by the rate of the fastest channel. For example, suppose we want to record four channels of data, one at 2kHz and the other three at 20Hz. The sample throughput rate in this case would be 8kHz (4 channels × 2kHz = 8kHz). See also Sampling Different Channels at Different Rates.

Minimum and maximum values for sample rate vary by instrument see your hardware manual for details. For example with a DI-220, the minimum sample rate that can be entered in the text box is .007 while the maximum sample rate that can be entered is 70,000 (however, you may not be able to reliably store data to disk at sample rates over 40,000. This will be explained in more detail later in this description).

In order to enter a sample rate of less than 1 in the Sample Rate text box (effectively sampling about once per minute) you may also be required to lower the maximum sample rate (burst rate). See Preferences > Maximum Sample Rate.

The following diagram illustrates the relationship of maximum sample rate (burst rate) to sample rate.

As can be seen from the illustration, the maximum burst rate must be set to the low end of its range to get a sample rate less than 1. The maximum burst rate can be restored to its previous value if desired.

The Input Buffer Size in KB value is displayed for informational purposes only in this text box, it can not be directly adjusted by the user. It indicates the size of the input buffer, which is where the acquired data will be temporarily stored (in “valuable” or scarce, contiguous Global DOS memory). The amount of memory allocated for this buffer is a function of three factors: the current sample rate, how much memory is currently being used by your computer, and the input buffer size limit (maximum amount of your computer’s memory you have dedicated to this buffer, specified from the Preferences command on the Edit menu - see Buffer Size). The Disk Buffer Size in KB value is also displayed for informational purposes only and can not be directly adjusted by the user. It indicates the size of the disk buffer, which is a temporary storage place (in “cheap” or easily-attainable, non-contiguous memory) for the acquired data before being written to disk.

However, with WinDaq Acquisition you can directly adjust or modify buffer size and sample rate, two factors that govern gap-free data acquisition.

The Preferences command on the Edit menu allows you to specify a buffer size ranging from 16kB to 128kB. The larger the buffer size, the greater the chance of acquiring gap-free data at the maximum sample rate your computer can achieve. However, the larger the buffer size, the more memory it uses, thus leaving less (perhaps not enough) for running other programs. If you never run other programs simultaneously with WinDaq Acquisition, then conserving memory is not an issue. However, if you like to run WinDaq Acquisition simultaneously with a spreadsheet program or a data analysis program, then you could limit the amount of memory allocated to the input buffer so the other applications have enough memory to run. See Buffer Size.

The Sample Rate dialog box allows you to specify sample rate. The sample rate used to determine buffer size is the old or previous sample rate value (before any changes were made with this dialog box). The amount of buffer space allocated is proportional to the sample rate. WinDaq Acquisition automatically and transparently allocates the correct amount of buffer space when you input a sample rate. However if you have increased the buffer size (Buffer Size), there is a chance that the sample rate you enter is too high for the amount of buffer space you have allocated. If this is the case, the S/s (F3): value in the status bar will be displayed in reverse video

This serves as a warning that you might not be able to reliably store data to disk with the current combination of sample rate and buffer size. See Different Ways of Allocating Memory. If the instructions therein do not help, you have two options: (1) lower the sample rate; or (2) increase the buffer size.

When the desired sample throughput rate is entered, click the OK button or press the Enter key to close the dialog box.

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