Distance

The following procedure illustrates how to create a math channel in the DataLink II software to calculate the distance a vehicle has traveled using the G-Meter, which is available on many of the Racepak systems.

In order to use create this channel, you will first need to create the G/M MPH channel. If you haven’t already done so, click here to view the G/M MPH channel.

Next, open the file to which you wish to add the new channel. If it is a run file, simply open it from the ‘File’ menu in the DataLink II software. If you wish to add it to your configuration file, so the channel will appear in all subsequent downloaded files, the select ‘Open Car Configuration’ from the ‘File’ menu, and select the appropriate configuration file from the available list.

Once the desired file has been opened in the software, select the ‘Channel Maintenance’ option under the ‘Edit’ menu.

Click on the channel in the list where you would like to insert the new channel. In this example, we have selected a position after the last channel, so the position after ‘Pan Press’ has been highlighted. Click on ‘Easy Insert Channel’.

Now we need to select the type of channel we will be inserting. Since we are going to be using calculus to integrate the G/M MPH readings, we should select ‘Integrator’ from the list. By default, the only available type in this instance is expression (EXPR). Click ‘OK’.

Select the ‘G/M MPH’ channel you already created in the earlier example. To back out the distance value, we will need to divide out the constant we used when calculating ‘G/M MPH’. Therefore, divide ‘G/M MPH’ by 0.6818 as shown in the expression below.

From this dialog, you can see the math which takes the speed of the vehicle calculated from integrating the G-Meter (‘Accel G’) and then dividing out the constant of 0.6818, which is the result of converting feet to miles and seconds to hours.

It is important to note that in order for this channel to display correctly, you must ensure the following items are correct:

  • The G-Meter is mounted flat and level
  • The start time has been zeroed using the G-Meter value
  • The “Start Integrator From Zero” checkbox has been checked

Also, be sure to scale the minimum and maximum values correctly for your application. Many cars use ‘0’ as the minimum value and ‘1500’ as the maximum. In this example from a Top Fuel car, the maximum has been set to ‘1500’. You may wish to change the result units to ‘FT’.

Simply click ‘OK’ to add the channel to the list, and then ‘OK’ a second time to return to the main screen of the DataLink II software. You should see the channel button ‘Distance’ appear in the location into which you inserted it. If you are satisfied with the results, be sure to click ‘Save’ from the ‘File’ menu.

For questions or assistance in adding these channels to your system, please contact us at Performance Data Systems at (949) 652-6300 or email us at support@racepds.com.