SPEEDBOX Pulse Output
The pulse output is designed to allow the SPEEDBOX to be used as a drop-in replacement for 5th wheel type systems, and is extremely configurable to allow the SPEEDBOX to be configured to match the user’s existing pulse data acquisition equipment. By default the pulse output is proportional to combined (GPS + inertial) speed, although it can be configured to output GPS only speed for applications with confounding pitching moments, such as high seas.
The pulse type can either be a fixed width, in which case the pulse high time can be set between 10μS and 1000μS, or a 50% duty cycle, in which case the high time and low time are equal and are a function of the vehicle speed. For both pulse modes, the low and high pulse levels are 0 and 5V respectively. The output impedance is 50Ω. In each case the number of pulses per meter can be set between 1 and 400. A higher value of pulses per meter will give greater resolution, but will saturate at a lower speed. A lower value of pulses per meter will give lower resolution, but will allow a higher speed to be reached before saturation occurs. The configuration software shows the maximum speed that can be represented before saturation for any entered value of pulse configuration.
It is also possible to configure the pulse output to output a 1Hz timepulse, in which case the rising edge is precisely synchronised to the second boundaries of GPS (and UTC) time.
Refer to the SPEEDBOX configuration instructions for further information on how to configure the pulse output.