Ammeter

When M is a voltmeter an indication of the energy difference between the reactants and products is obtained (see below). A current passes when M is an ammeter, and if a little potassium thiocyanate is added to the Fe (aq) a red colour is produced around the electrode, indicating the formation of iron(III) ions in solution the typical bromine colour is slowly discharged as it is converted to colourless bromide Br . 

Surface resistance is measured by placing two electrodes on the surface of the object to be tested. A d-c voltage is appHed to one electrode and an ammeter is attached to the other electrode. The current travels from one electrode to the other by traveling across the surface of the object. When the current is measured and the appHed voltage is known, resistance can be calculated by the formula resistance = voltage/current. 

Control system. Current source (batteries), ammeter, voltmeter, instrument panel, and so on. 

Separated Anode/Cathode Realizing, as noted in the preceding, that locahzed corrosion is usually active to the surrounding metal surface, a stress specimen with a limited area exposed to the test solution (the anode) is elec trically connec ted to an unstressed specimen (the cathode). A potentiostat, used as a zero-resistance ammeter, is placed between the specimens for monitoring the galvanic current. It is possible to approximately correlate the galvanic current 7g and potential to crack initiation and propagation, and, eventually, catastrophic fail-... 

The drop of potential method or voltmeter-ammeter method... 

The height (we may consider it from the bottom line) of the indicating instruments such as a voltmeter and an ammeter, which the operator may have to read often, is also recommended to be no higher than 2000 mm or less than 300 mm from ground level. 

Thermal maximum demand ammeters 4 to 8 VA Power factor (p.f.) meters 5 VA... 

These are employed for the measurement of power circuit currents through an ammeter, kW, kWh or KVAr and power factor meter, or similar instruments requiring a current measurement. They must have a specified accuracy class as in lEC 60044-1 and the secondary current substantially proportional to the primary within a working range of about 5-120% of its primary rated current. They... 

Ammeter selector switch 32. Over current ground fault... 

The same lest can also be conducted with the help of a battery, voltmeter and an ammeter, as illustrated in Figure 22.8. The voltmeter must now indicate the same reading at all three locations. When V becomes constant, read the current /. Then the ground resistance... 

Figure 22.8 Measuring the ground resistance with the help ot an ammeter and a voltmeter...

I When the system voltage is linear (an ideal condition that would seldom exist) but the load is non-linear The current will be distorted and become non-sinusoidal. The actual current /, (r.m.s.) (equation (23.2)) will become higher than could be measured by an ammeter or any other measuring instrument, at the fundamental frequency. Figure 23.13 illustrates the difference between the apparent current, measured by an instrument, and the actual current, where / = active component of the current... 

To irionitor the health of i capacitor unit it is tidvisable to provide an ammeter in each phase. When it is fotmd. that there is an tmbalance not caused by oltage unbalance then further investigations may be conducted to replace the defective unit(s) before a majoi fault occurs. 

The potential dependence of the velocity of an electrochemical phase boundary reaction is represented by a current-potential curve I(U). It is convenient to relate such curves to the geometric electrode surface area S, i.e., to present them as current-density-potential curves J(U). The determination of such curves is represented schematically in Fig. 2-3. A current is conducted to the counterelectrode Ej in the electrolyte by means of an external circuit (voltage source Uq, ammeter, resistances R and R") and via the electrode E, to be measured, back to the external circuit. In the diagram, the current indicated (0) is positive. The potential of E, is measured with a high-resistance voltmeter as the voltage difference of electrodes El and E2. To accomplish this, the reference electrode, E2, must be equipped with a Haber-Luggin capillary whose probe end must be brought as close as possible to... 

Current-controlling rectifiers are constructed in general on the same circuit principles as potential-controlling rectifiers only with them, the protection current is converted to a voltage via a constant shunt in the control circuit and fed in as the actual value. With devices with two-point control, the ammeter has limiting value contacts that control the motor-driven controlled transformer. 

Transformer-rectifiers should have an ammeter to indicate the current and a high-resistance voltmeter to indicate the potential at the protection station. 

Pure aluminum is used in the electrolysis protection process, which does not passivate in the presence of chloride and sulfate ions. In water very low in salt with a conductivity of x < 40 yUS cm" the polarization can increase greatly, so that the necessary protection current density can no longer be reached. Further limits to its application exist at pH values < 6.0 and >8.5 because there the solubility of Al(OH)3 becomes too high and its film-forming action is lost [19]. The aluminum anodes are designed for a life of 2 to 3 years. After that they must be renewed. The protection currents are indicated by means of an ammeter and/or a current-operated light diode. In addition to the normal monitoring by service personnel, a qualified firm should inspect the rectifier equipment annually. 

Monitoring the cathodic protection of filter tanks extends to the control of protection current levels with the use of ammeters and/or current-operated light diodes. The internal condition of tanks should be inspected visually every 2 years. 

Strength. -messer, m. current meter specif., (Elec.) ammeter, amperemeter,... 

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