But my words like silent raindrops fell, and echoed in the wells of silence.
– from The Sound of Silence, Paul Simon
Just drop a piece of stone, if you are going to figure out how deep the water is inside the well. One can easily estimate depth of the well and the amount of filled water by counting time to reach the water and hearing sound of splash.
Except in case of simply monitoring physical property of an object at given condition, like taking temperature or observing spectrum of starlight, most of experiments are projected in such a way of giving a certain stimulus to the object, from which informations are to be obtained, and by measuring its response.
Among the stimulations, which can be applied in various forms and manners depending on characteristics of information to be obtained from experiments, the most common is an electrical stimulation outputting precise signal with wide range of frequency band from DC to sub-nano second scale.
Unless the electrical current of the device under test applied by an electrical stimulation is substantially large, a function generator is typically used for signal generation. However, in case of applying significantly larger current signal as an electrical stimulation, a design of the stimulation circuit requires careful considerations such as choice of current amplifier, its response time, interface to measurement circuit, and synchronization, etc..
In a design element side of current-carrying electrical stimulation system, McScience developed a QUINTEST module, a functional electric power source-meter providing five major stimulus signals and five major measurement interfaces, and employs it as a master component for various lines of experiment and test systems.
The most commonly used electrical stimulation signals in ordinary experiments are DC, step, ramp signals and periodic square pulse and sinusoidal wave. For example, OLED unit cell is powered by constant-current (CC) or constant-voltage (CV) at DC or pulse mode, and such power driving method is quite similar to the charging method of rechargeable battery. Peculiarly for discharging of battery, constant-power (CP) and constant-resistance (CR) feedback controls are optional. The voltage ramp is essential not only for I-V characterization of diode devices such as solar cell and OLED, but also for cyclic voltammetry of electrochemical cell and rechargeable battery. For frequency response and transient analysis, sine wave and pulse signal are employed, respectively.
Pulse signal driving for semiconductor device having diode structure requires CC control at forward bias and CV control at reverse bias, and in this case the pulse by CC-CV switching (PCVS) technique applies.
Likewise, there are several types of electrical stimulations commonly used for the characterization of devices at different applications, and based on advanced power control technology, McScience provides various experiment and test systems in combination with diverse measurement technologies.
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