Internal resistor

In the mid-IR several type of sources are used. They are either a lamp filament (Figure 10.13), or a hollow rod, 1-3 mm in diameter and 2 to 4 cm long, made of fused mixtures of zirconium oxide or rare earth oxides (Nernst source) heated by Joule effect by the means of an internal resistor (for example Globar ). These sources are heated to 1500 °C, without a protective shield. They dissipate power of the order of a hundred watts by emitting radiation over a large domain ranging from visible to thermal IR. A maximum is observed for A = 3000/T (A in... 

Fig. 4.86. Equivalent circuit of a photodiode with internal capacity Cs, series internal resistor parallel internal resistor Rp, and external load resistor Rl...

Drift due to high power is usually due to internal resistor heating. It is different from thermal aging in that the heat is generated at the point-to-point metal contacts within the resistor film. When a resistor is subjected to heat from an external source, the whole body is heated to the test temperature. Under power, local heating can result in a much higher temperature. Because lower value resistors have more metal and, therefore, many more contacts, low-value resistors tend to drift less than higher value resistors under similar loads. 

The milliampere settings make the meter especially vulnerable to being damaged by excessive current, since there is no internal resistor being used to act as a limiter. If a battery is directly attached to the meter by mistake, with no external resistance such as the transformer, the fuse will blow out, and the meter will no longer operate. The back cover can then be taken off, usually with a small Phillips head screwdriver, and in this case the fuse could be replaced with a 315 ma fast-blow type. 

The circuit design tools identify the resistors and capacitors that must be added to make an electronic circuit functional. The tools simulate circuit operation and size the resistors and capacitors as appropriate. Whether a resistor is purchased and mounted on the board surface or formed inside the board from a layer of resistive material has little effect on the electrical operation of a circuit. Therefore, if many resistors can be formed inside the board from the same series of chemical steps, the inclusion of perhaps thousands of internal resistors costs no more than adding one internal formed resistor. The critical economic analysis is to find the cost of adding internal formed resistors and then dividing by the number that can be nsed internally to see whether embedded resistors inside the board make sense. 

Figure 4.25 illustrates a numerical model of the single section of the feeding circuit. The substation is expressed by a series circuit of a diode D, an internal resistor R, and a voltage... 

If a voltage regulator is installed into a substation, the substation can be simply modeled with a small internal resistor = 1 mQ and an ideal source E of 1690 V, which is the target voltage of the voltage regulator. 

H. T. Sa whill and co-workers, "Low Temperature Co-Firable Ceramics with Co-Fired Resistors," International Society of Hybrid Microelectronics Proceedings, 1986, pp. 473—480. 

Electronic Applications. The PGMs have a number of important and diverse appHcations in the electronics industry (30). The most widely used are palladium and mthenium. Palladium or palladium—silver thick-film pastes are used in multilayer ceramic capacitors and conductor inks for hybrid integrated circuits (qv). In multilayer ceramic capacitors, the termination electrodes are silver or a silver-rich Pd—Ag alloy. The internal electrodes use a palladium-rich Pd—Ag alloy. Palladium salts are increasingly used to plate edge connectors and lead frames of semiconductors (qv), as a cost-effective alternative to gold. In 1994, 45% of total mthenium demand was for use in mthenium oxide resistor pastes (see Electrical connectors). 

Incidentally, don t blindly add a bypass capacitor in parallel with the (upper) feedback resistor, as suggested. That feedforward capacitor introduces another zero in the loop and can cause the system to go unstable. You should realize that this family of devices has a full-blown internal Type 3 compensation, so it even has an internal zero to emulate an external ESR zero. That is why this family is supposed to be able to handle ceramic capacitors at the output. If you introduce yet another zero (via the feedforward capacitor as suggested), you could have one too many zeros. And ultimately, your design could be one, too (a zero). 

Now measure one of your resistances with the multimeter as follows. Insert the wire ends into two sockets on the socket board so that they are not connected internally, such as in sockets FI and F5. (You will have to bend the end wires at about a 90° angle.) Measure the resistance with your multimeter by setting the selector switch to measure resistance and then contacting the lead tips to sockets that make contact with FI and F5, such as G1 and G5. You may have to adjust the selector switch to the proper range for the resistor being measured. Record the value in your table. Measure all the other resistors in the same way. Determine if the accuracy of each, as indicated by either the gold or silver stripes, is correct based on your data and comment on this. 

Next, measure your resistors connected two at a time in series. This means that two of the resistors are connected end to end. When two resistors are connected in this fashion, the total resistance is the sum of the two. To do this, use the socket board and insert the wire ends of one resistor into sockets FI and F5 (as in step 5), for example, so that the ends are not connected internally. Then insert the wire ends of the other resistor into sockets G5 and G9, for example. Since G5 and F5 are connected internally, this connects both resistors in series. Now measure the total resistance by touching the lead tips of the multimeter to sockets HI and H9. Record the individual values of the two resistors, the sum of the two, and the measured value of the sum in another table (four columns) in your notebook. Repeat with several different combinations. Comment on the agreement (or lack thereof) between the calculated and measured values. 

The cells shown in Figs. 28 and 29 all operate according to the same principles, which have been developed by Arup. The interior of the cell acts as the anode chamber, and a metal oxide cathode placed inside the cell in an alkaline electrolyte acts as the counter electrode. The hydrogen flux across the integrated membrane (coated with palladium on the internal surface) can be measured as the potential drop across a resistor placed between the membrane and the counter electrode. 

Figure 1 A distributed resistor network models approximately how the apphed potential is distributed across a DSSC under steady-state conditions. For various values of the interparticle resistance, fiT,o2, and the interfacial charge transfer resistance, Rc the voltage is calculated for each node of the Ti02 network, labeled Vj through V . This is purely an electrical model that does not take mobile electrolytes into account and, therefore, potentials at the nodes are electrical potentials, whereas in a DSSC, all internal potentials are electrochemical in nature.

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