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logging.md

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Logging

Logging allows signal data to be saved without message data bytes and IDs. The Logging screen (Figure 1) is accessed from the Measurement menu.

Figure 1: The Logging screen.

Selecting a Signal Group

Logging uses the same signal groups as the Signal Plot and Signal List features (Figure 1:). Start by choosing the desired signal group via the Signal Group to Log drop-down list. To change the signals in that group, click on Select Signals. The and buttons can be used to add and remove signal groups.

You can also press the Copy Selected Group button () to duplicate the currently-selected signal group.

Enabling Logging

Enable the Logging feature for the selected signal group by clicking the checkmark next to Log This Signal Group (Figure 1:). This will activate most of the other controls in the window.

Logging Status and Data

While Logging is active, its status is shown in the upper right corner (Figure 1:). You can view data as it is being collected by pressing the View Data button.

Logging Setup

This option area sets primary parameters for logging (Figure 1:). These are the options found in this area:

  • Log at Constant Rate / Log All Updates: Determines whether all data is logged or it is instead time-sampled. Choosing Log All Updates will disable the Log Rate options below.
  • Log Rate (sec/sample): The frequency at which data is sampled and logged.
  • Save when data changes only: When enabled, new entries are created only when data changes; this can help reduce storage requirements.
  • Log File: The name of the file where data is to be stored.
  • Log File Creation Options: Specifies when to reuse existing log files or start new ones, and under what circumstances.
  • Ignore formatting on signals and save as analog values: When checked, analog values are saved without the specified formatting setup for the signal.
  • Write CSV File / Write MDF File: The file format for saving data; at least one must be checked.

Start Logging

The parameters in this area (Figure 1:) dictate when Vehicle Spy begins logging data. The two options are:

  • Start Automatically: Logging begins immediately when Vehicle Spy starts.
  • Start on Equation: Vehicle Spy begins logging when the defined condition evaluates as True. Selecting this option enables the equation button (), which you can click to select the start condition using the Expression Builder.

The Enable Pre Start Collection option allows the capture of a number of seconds of data immediately preceding the start trigger.

Stop Logging

Choose an option in this box (Figure 1:) to tell Vehicle Spy when logging should stop:

  • Stop Automatically: Logging stops when Vehicle Spy does.
  • Stop on Equation: Vehicle Spy stops logging when the defined condition evaluates as True. As with the start condition, you can click to specify the stop condition.
  • Stop After a specific amount of time: Logging stops after a specified number of seconds.

The Zip file when stopped option tells VSpy to compress the logged data in a zip file to save space.

Invalid Signal Handling

An invalid signal can occur when signal data is cleared in a function block, or when Vehicle Spy starts before signal data is available. The program offers several options to deal with such conditions (Figure 1:): use the last value, leave the value blank, or replace the invalid value with one specified in the Replace with Value field. This last option is handy if other programs are going to chart or graph this data; blank or text entries can be replaced with a value that is still able to be graphed, but is known to be invalid, so it is not confused with valid data.