Constant voltage mode

P 8] The resistance between the electrodes was measured in situ. The power supply was operated in constant-voltage mode [96], A low-volume tracer was injected with a syringe and then applied a voltage of 4 V across the channel. The current was of the order of pA and was below the resolution level of the power supply (10 mA). 

The power supply to the electrolyser was a Model 710 from The Electrosynthesis Company, Inc. of Lancaster NY. It was operated in constant current mode rather than in constant voltage mode. The maximum current and maximum voltage available was 50 amperes and 20 volts, respectively. In addition to current measurement provided by the power supply, a calibrated shunt was connected to the output to allow for independent measurement of current. Voltage taps independently connected to the cell electrodes were connected to the data acquisition system (DAS). The instrument signals from thermocouples, pressure gages, and flowmeters were connected to the DAS, which was comprised of a Dell computer with special acquisition boards and Labview software. Observations and some data were manually recorded in a laboratory notebook. 

During the period of the current decay, there are two competitive processes, densification to form the barrier layer and dissolution of barrier layer to form the porous layer. Under the high electrical field strength (constant voltage mode), the densification of the aluminium oxide films is favoured for process durations shorter than 3700 s. When the constant voltage was kept for a long anodisation time (beyond 10900 s), the dissolution of the aluminium oxide film becomes more dominant. Thus, the film could be contaminated by inward migration of the electrolyte into the film or by formation of micro-voids. 

The power supply, operated in the constant-voltage mode, had a stability rating of 0.05% or 10 mv for 8 hr (after warm-up), with a ripple of 0.25 mvrms maximum. The short-term stability of the voltage was checked frequently throughout the measurements and found to be stationary to within 15 /tv. 

With the decreasing of the pressure difference in the constant voltage mode, the output current continue to decrease to certain rules when the current is reduced to 0, then the battery is fully charged, the charger stop charging or continue to trickle mode charge (WANG 2004). 

Constant voltage mode (CV). Here, the voltage across the sensor is kept constant and the change needed to keep the voltage constant is related to the shear stress. 

Constant voltage mode In this mode a constant output voltage is maintained by the rectifier. The applied current then changes with variations in circuit resistance. Low concrete resistance, often associated with increased risk for corrosion damage, can result in increased current output. It should be noted that in this mode, the rebar potential is not necessarily constant. It can again be monitored with a reference cell. 

Fig. 5. Cycle test of an EDLC using DEME-BF4 as an electrolyte at 100 °C. The test cell was charged by a constant ourent-constant voltage mode from V = 0 to 2.5V at a constant current (CC) / = 15 mA and then charged to keep constant voltage (2.5 V) for 15 min and discharged to OV by CC mode.

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