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Automation Technologies 2/2014

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Automation Technologies 2/2014

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Machine Vision previous page Back to current issue cope without any copying process. The resulting overhead is very low, i.e. there is only a small difference between the gross and net data rates. Speaking of real-time capability of Vision systems usually refers to different points in the system where latency times and time-related jitter may occur. The latency time includes the averaged absolute time, beneficial to select a USB 3.0-camera with the same sensor to minimise the change effort. Alternatively, a deviating sensor of the same or similar sensor size and sensitivity is an option. The housing size of the USB 3.0-camera should be similar, but never larger than the previously used FireWire-camera (figure 2). The setup behind the camera usually is a little FireWire is slowly but steadily losing support in the PC world. It will disappear from the market in the medium term. while jitter is the time-variation from each same process step to the next same process step. The timerelated jitter is the more important aspect for determining in advance when the next process step that depends unconditionally on a previous one may happen. When performing measurements for real-time capability, it turned out that USB 3.0 has shorter latency/jitter times than FireWire does, and is the more beneficial interface in the sense of real-time capability. Replacement effort: changes to hardware… In case of replacement, changes arise to the hardware and software. As an example, we are looking at a single-camera system for classic object inspection. The complete mechanics in this system are adjusted to this object, i.e. the distances are coordinated with the lens used, the chosen sensor format and its resolution. The specific lighting may also be adjusted to it. If this setup is to be equipped with USB 3.0, it is simpler: The camera is connected to the PC via a FireWire-cable and plugged either into a PCIexpress card or the sockets directly connected to the mainboard. For precise triggering, another cable may be used for hardware triggering at the camera. On the PC-side, the cable and either the entire PC hardware or the PCIexpress card must be replaced. … and software The integration effort for software may vary much more strongly. Two extremes can be differentiated. n Version 1: Proprietary, DCAM-based software environment. The proprietary software supports only DCAM-compatible cameras and cannot be used as easily for cameras with newer interface standards such as the USB3 Vision. The software interface must be reprogrammed for the GenICam standard. The good news is that porting to GenICam is only required once to be ready for other current and future Machine Vision software interfaces as well. GenICam is the standard that all interface technologies have to meet. AUTOMATION TECHNOLOGIES 2/2014

Machine Vision 03 Amortisation of the investment: Switching to USB 3.0 pays off purely from the point of view of procurement 02 Hardware and software changes are required when switching from FireWire to USB3.0; the figure shows a single-camera system for classic object inspection n Version 2: GenICam-based software environment. Only slight adjustments are required. Ideally, the software environment has all drivers for USB3 Vision and camera control included in an update. A look at economic efficiency The calculation example in figure 3 shows how the change to USB 3.0 will pay off from the point of view of procurement. Switching to a USB 3.0-model with the same sensor, mainly expenses in the software area are required to adjust the software interface to the new camera interface. A smaller share is additionally required for hardware to attach the camera and install USB 3.0 with cable and ports. Using the same sensor means that no adjustments to the lenses, machine mechanics or lighting are required. The comparison shows that the break-even point will be reached within the first year. From the second year onwards, savings in the larger five-digit area are possible. The example is based on a number of 100 cameras. The costs for cables and hardware have not been considered, with savings expected here as well (USB 3.0 hardware setups tend to be cheaper by 20 %). AUTOMATION TECHNOLOGIES 2/2014