Power telemetry

As has already been mentioned, as of 2011, the commercial deployment into this space has been very Hmited. Here the market leader, or to be more accurate the market pioneer, is SEC Energy. Along with its distributor partner in the UK, UPS Systems, they have installed 20 EFOY units at the Elan Valley Reservoir to power telemetry equipment. The direct methanol fuel-cell systems use methanol, and with their 281 canisters there is sufficient energy to power the equipment 24 h per day for a minimum of 300 days. This is the largest project of its kind to date. 

Power efficiency, defined as the ratio of the power delivered to load over the total power dissipation, is the most important parameter in designing power telemetry system. To optimize power efficiency under physical constraints, an accurate solution for power efficiency in terms of design parameters is desired. Earlier work in the literature provides power efficiency formulae based on linear models [106,107]. Although such linear models provide design insights, they are oversimplified for the purpose of optimization. In this section, an expression of the power efficiency is derived. Based on derivations, the optimal component values are obtained and the fundamental upper limit of the power telemetry is concisely represented as a function of the quality factor Q) and coupling coefficient. 

A general equivalent model of the power telemetry is illustrated in Fig. 25. Due to the rectifier and the time variant current loads, the equivalent model is nonlinear. The power efficiency of the telemetry system is defined as... 

Fig. 25 A nonlinear equivalent circuit model for epi-retinal power telemetry. It consists of an external class E power amplifier, an inductive coil pair, a resonant amplifier, a rectifier, and time variant current loads...

In this section, an analytical model is presented to calculate the of a coil with given geometry parameters. In order to reduce the AC resistance, and thereby the Q at high frequencies, litz wire is widely used in biomedical power telemetry to transmit both power and data, as shown in Fig. 29. 

Zhou M, et al. (2006) A transcutaneous data telemetry system tolerant to power telemetry interference. Proc. IEEE 28th EMBS Conference, pp. 5884—5887, Sep. 2006. 

When the MWD systems are battery powered and have a downhole recording capability or use an electromagnetic telemetry, logging measurements can be repeated each time the bit is pulled out or run into the borehole. This new capability provides a way to map the progression of the filtrate front in the permeable formations. 

Electromagnetic Telemetry. The electromagnetic telemetry is usually powered downhole with batteries. Parameters such as gamma ray, resistivity and temperature, can be transmitted while tripping up or down. Since a two-way communication is possible, the system can be switched to a logging only mode to transmit only the logging information. 

To meet the challenges posed by horizontal drilling in particular, a system has been developed to make the measurements at or near the bit and transmit them to the mud telemetry section of the MWD bottomhole assembly. The resistivity at the bit tool is similar to the toroidal resistivity tool described in the section titled Resistivity Logs. As shown in Figure 4-297, the Anadrill geosteering package includes below the Power Pack mud motor ... 

Wireless pH measurement systems have been used in clinical studies. Unlike a standalone pH electrode, a power source, control electronics, and a signal transmitter have to be incorporated into a wireless system. Watanabe et al. [138] have reported a wireless pH sensor to record salivary pH continuously. The sensor system transmits pH data via a telemetry system for about 19 hours with a 3V lithium battery (190mAh). The error of transmitted pH data was less than 0.15 pH in the range of pH 5.0 to 9.0. 

A glucose sensor system consisting of an oxygen electrode and a glucose oxidase electrode was recently implanted into the vena cava of a dog (McKean and Gough, 1988). The sensors operated in the potentio-static mode and were connected to an implantable telemetry system. Both the enzyme stability and the power consumption allowed operation of the system for three months. 

In addition to use in implanted devices, small batteries are the power source for hand-held and portable instruments some applications are telemetry receivers, pacer system analyzers, pacemaker programmers, and Holter monitors. 

Intrinsically safe type i protection is not applicable to electrical power equipment. It is mainly intended for electronic measuring and control circuits i.e. instrumentation and telemetry. The principle behind i protections is that a circuit and its devices do not have sufficient operating energy or stored energy to cause a spark that will ignite the gas-air mixture. A spark can occur but it must be inherently too weak to ignite the mixture. There are two sub-divisions of type i , namely l and it . The type ia has a more stringent specification than i, and is therefore allowed to be used in a Zone 0 area. Type ifc equipment cannot be used in a Zone 0 area. 

The second effect of the harmonic currents is to induce harmonic emfs by mutual coupling, and consequently additional harmonic currents, into cables that are run close to the power cables feeding the driving motor or its controller. This is particularly troublesome for low power cabling e.g. computer cables, instrument cables, telemetry systems, telephones and communications cables, electronic circuit cables. 

Most implantable systems for neuromuscular application consist of an external and an implanted component. Between the two, an inductive radio-frequency link is established, consisting of two tightly coupled resonant coils. The link allows transmission of power and information, through the skin, from the external device to the implanted pulse generator. In more advanced systems, a back-telemetry link is also established, allowing transmission of data outwards, from the implanted to the external component. 

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