New-Tech Europe Magazine | Feb 2017

Sensors Special Edition

of the required connector resistance is strongly dependent upon the devices in the circuitry the connector must interconnect. For many devices, high connector resistance - hundreds of milliohms - can be tolerated. E n v i r o n m e n t a l considerations: Harsh environments, such as deep ocean or vibration sensitive surroundings, may constrain the traditional connector application and design. There may also be harsh and safety-critical applications, such as gaseous environments, which limit the application of contact technology. Corrosion: Corrosion occurs in many forms and can be classified by the cause of the chemical deterioration of a metal. The most common form of corrosion is rust or ferric oxide. Galvanic corrosion, or dissimilar metal corrosion, occurs when two different metals are located together in a corrosive electrolyte. Movement: Cabled solutions are generally constrained in their movements. Wear and tear on cables coupled to motor-driven, rotating subsystems, such as robotic arms, can lead to downtime, severely affecting productivity. A classic example is a robotic arm, which may have to move along multiple axii. Traditionally, rotation with reliable connectivity is achieved using slip rings that are connected to stationary rings via brushes. Cables are used to position these copper rings in close proximity to enable physical contact with carbon brushes. Mating cycles: The connector may be designed to meet specified mating frequency and cycles from a few hundred to thousands. Cycle-life requirements affect the design and materials used in manufacturing the connector. Other factors: Cost, size, efficiency and the ability to transmit over certain distances may also be

Data Link

Pro

Challenges

Capacitive coupling Low EMI. Also suit- able for ring struc- tures

Requires significant plate area, challeng- ing for tiny rotating couplers, sensitive to changes of material/ fluids Should generate a circular polarized wave to support rota- tion No high bandwidth without OFDM, but that increases la- tency Low bandwidth (sub Mbps) Low bandwidth (10- 100kbps) Sensitive to dust and dirt, precision optics & lenses needed

RF, 60 GHz (OOK, ASK, QAM)

Large bandwidth (>1Gbps), low laten- cy (nanoseconds) Easy near field an- tenna design (simple loop), RF solutions widely available Easy near field an- tenna design (simple loop), RF solutions widely available

RF, 2.4/5 GHz (e.g. GFSK, MSK, ASK)

RF, sub GHz (e.g. FSK)

Via ICPT power link No separate antenna needed

Optical

Very high bandwidth possible (>10Gbps)

Figure 1. There are numerous options for a contactless data link, including 2.45-GHz RF, but power links are for now best achieved using inductively coupled power transfer

approach. As mentioned, a separable connection provides a separate connection between two elements of an electronic system without unacceptable degradation of performance. The separable connection and unacceptable performance depend on the connector application and its electrical and environmental application. Factors to consider when choosing a connector include: Power distribution: Joule heating, which is proportional to the connector resistance, can result in increases in the connector operating

temperature, a major factor in connector degradation. Both magnitude and stability of contact resistance are critical for power connectivity. Arcing is also significant in power applications, especially where there are hazardous gas environments. Signal distribution: Signal distribution requirements center around maintaining the integrity of the signal waveform. For high-data- rate systems, this may involve controlled-impedance connector designs and careful attention to signal-to-noise ratios. The magnitude

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