The Dual Antenna VBOX Speed Sensor (VBSS100SL) is a high-accuracy, 100 Hz, GPS/GLONASS system. It combines high-level accuracy and test repeatability with the ability to measure slip and pitch/roll angles at 100 Hz.
The VBSS100SL package includes VBOX Manager, which enables the user to set up the dual antenna separation, change the dynamic modes and level and align the antennas.
You can use the Dual Antenna BOX Speed Sensor straight from the box. It will output digital and analogue signals according to the default settings. You can change these settings in the VBOX Setup Software. Learn how to do this here.
The Dual Antenna VBOX Speed Sensor should be securely mounted inside the vehicle, level with the ground. There are holes in the ground plate that can be used to fasten the Speed Sensor to a suitable location in the vehicle. Make sure that the surface with the LEDs and pin information is up.
Even though installing and using the Dual Antenna VBOX Speed Sensor is intended to be fast and simple, you must pay careful attention to the placement of the antennas.
Antenna A is the primary antenna, on which all calculations are based. You should place the primary antenna relative to where you wish to take your measurements. For example, if you wish to make measurements from the centre of the vehicle, you achieve this by placing the primary antenna at the centre of the vehicle or translating the position using the slip angle translation function in VBOX Manager.
The measured distance between the antennas should be the straight-line distance between the antennas regardless of the mounting angle. It is not the 2D distance between the antennas as viewed from above.
Use the supplied tape measure to ensure accurate antenna separation.
Important: It is essential that the separation between Antenna A and Antenna B is exactly the same as the separation value set for the Speed Sensor via the VBOX Manager or the VBOX Setup Software. If the distance is incorrect, your data may be inaccurate or not captured at all.
Interfacing with the VBOX Speed Sensor
You can use the VBOX Speed Sensor in several different ways, and it is common for the end-user to integrate the speed sensor connector into their own wiring harness. You can purchase a mating connector, Deutsch ASDD606-09PN, from Racelogic for this purpose.
You should connect the GNSS antenna before you connect power to the Speed Sensor. This is because the Speed Sensor will look for a connected GNSS antenna and automatically adjust its gain for optimum performance from the connected antenna.
The GNSS antenna supplied with the Speed Sensor is a 5 V active antenna. For the best possible signal quality, it is important to maintain a clean connection between the antenna and the Speed Sensor. Before you fix the antenna to the Speed Sensor, make sure that there are no dust particles in either connector. Replacement antennas are available from your Racelogic distributor.
The antenna is a magnetic mounting type for quick and simple mounting to the vehicle roof. For optimum GNSS signal reception, make sure that the antenna is fitted to the highest point of the vehicle, away from any obstructions that may block satellite reception. The GNSS antenna works best with a metal ground plane underneath (a metallic vehicle roof is perfect for this).
Note that it is important to have a clear sky view when you are using any GNSS equipment. Objects in the surrounding area, such as tall buildings or trees, can block the GNSS signal and lead to a reduction in the number of satellites that are being tracked and could introduce reflected signals that can decrease the accuracy of the system. Clouds and other atmospheric conditions do not affect the performance.
GNSS antennas require a ground plane to operate correctly. This helps reduce unwanted reflections of the GNSS signal caused by nearby objects. Usually, the metal roof of a vehicle will perform this function, however, if a test requires the antenna to be placed either off the vehicle or on a vehicle that does not have a metallic roof, you must use a special ground plane antenna. This has an internal ground plane and can operate perfectly without the need to be mounted on a metal surface. Ground plane antennas are available from your Racelogic distributor.
Satellite Elevation Mask (Dual Antenna units only)
You can use this feature to improve GPS signal quality when nearby obstacles like trees and building are reflecting or temporarily obscuring the signal from satellites at low elevation. Raising the mask will cause the GPS engine to ignore satellites below the mask angle. You must use it carefully, though, as it also reduces the total number of received satellites.
You can change the elevation mask angle under the GPS tab in the VBOX Setup Software or by using a VBOX Manager.
You may need to perform a GPS Coldstart when:
- The GPS/GNSS engine has locked up.
- The Speed Sensor is struggling to acquire satellite lock
A GPS coldstart forces the GPS engine to reset its downloaded almanac of current satellite positions. This can be useful if the Speed Sensor is having trouble locking onto satellites, which typically occurs if the unit has not been used for several weeks or if it was last used a long distance (over one thousand miles) away from the current location.
After performing a GPS coldstart, leave the Speed Sensor powered up in a static location where the antenna has an unobstructed view of the skies until the ‘GPS’ LED becomes solid green.
How to perform a coldstart
- Open the VBOX Setup Software.
- Select the Speed Sensor from the drop-down connection menu and connect to the unit.
- Press the GPS Coldstart button on the General tab to activate the procedure.
- The LED's on the Speed Sensor will all turn red, and return to normal function when the coldstart procedure has been completed.
- Digital Input
- Connect the Speed Sensor to a PC using the RS232 connector of the RLCAB093 loom.
- If the Speed Sensor's Digital Input is configured to Lap Pulse mode, you can perform a coldstart by grounding the input while connecting the Speed Sensor to power.
- When this is done correctly, the LEDs on the Speed Sensor will all turn red before returning to normal function when the coldstart procedure has been completed.
Racelogic developed the VBOX Manager to control the operating functions of a Dual Antenna VBOX Speed Sensor. This section describes how to set up your vehicle with two antennas.
In the 'Dual Antenna' menu, select 'Dual Antenna Mode', scroll to 'Enable' and confirm. Now you should be able to see the full Dual Antenna system menu.
The most important factor for dual-antenna testing is the correct configuration of the separation distance between the two antenna centre points. This allows the Speed Sensor to acquire and maintain the dual-antenna lock. You need to measure the physical separation distance between the two antennas, as accurately as possible, and enter it into the Separation option in the Dual Antenna menu.
To provide a consistent reference, you should align the two antennas with the gold antenna connectors pointing in the same direction. This allows the system to perform a physical reference measurement, connector to connector.
Where possible, you should place the antennas on a level plane. The measured distance between the antennas should be the 2D distance between the antennas as viewed from above. It is not the straight-line distance between the antennas, regardless of the mounting angle.
Note: Whenever the physical antenna separation is altered, you need to change it accordingly on the VBOX Manager.
Roll Mode (optional)
With the Dual Antenna VBOX Speed Sensor, you can test roll and pitch measurements separately during testing. The VBOX Speed Sensor will be set up for Pitch determination by default. If you wish to set up your antennas across the width of the car to measure the roll angle, you must first toggle to enable 'Roll Mode' in the 'Antenna Orientation' menu. To toggle between Pitch Mode and Roll Mode, Highlight the menu, press the button, scroll to the required option and press the button again.
To measure the slip angle with the most accurate precision, try to get the alignment of the antennas as close as possible to the centre line of the vehicle. You can remove residual errors in the alignment with the 'Auto Align' feature in VBOX Manager.
The calibration process requires you to drive in a straight line for a short period of time, while maintaining a constant speed, which must be greater than 25 km/h.
Note: You need to remove any existing alignment offset from the previous setup by using the 'Clear' function. This must be completed before you start the Auto Align function.
Note: Any camber on the road or strong side winds will affect this alignment.
Selecting the 'Clear' option will remove any offset applied to the slip channel.
Note: You must have dual antenna lock to be able to perform this calibration.
The Pitch measurement uses the relative height difference between the antennas to calculate the Pitch Angle relative to the ground. If the roof of your vehicle is not perfectly flat in relation to the ground, then this will show up as a Pitch offset. You can automatically remove any offset by performing the 'Auto Level' feature on VBOX Manager.
Note: You need to remove any existing antenna level offset from the previous setup by using the 'Clear' function. This must be completed before you start the Auto Level function.
We recommend that you perform the Auto Level function on a flat and level section of road.
Selecting the 'Clear' option will remove any offset applied to the pitch channel.
Slip Angle Translation
In Dual Antenna mode you may wish to take slip measurements from other locations on the vehicle, for instance the centre of gravity or the slip over the wheels. You can set this by using the Slip Translation function in VBOX Manager. The five additional locations are set using Ahead/Behind and Left/Right offsets from the primary antenna location (antenna 1 in the picture below).
Gyro assistance: The Dual Antenna VBOX Speed Sensor has an integrated gyroscope that requires the unit to be mounted flat. The Gyro Yaw Rate will be used in the calculated slip channels as the signal to noise ratio is much lower than the GPS derived yaw rate. Therefore no extra noise is added during the slip translation process.
In section 1 on the diagram below, you can see a Left offset between the primary antenna and the target area for slip measurement. Same again for section 2, you can see an Ahead offset. You will need to apply these offsets with the VBOX Manager.
Each calculated slip point will require two offsets, Ahead/Behind and Left/Right for the VBOX to calculate the channels correctly.
Note: If you move the primary antenna, you will also have to measure the offsets again. For example when swapping between a pitch and roll setup.