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Programmable-logic controllers and operation
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
In applications requiring fine continuous control, closed-loop or negative feedback is provided where the sensed variable is compared to a user setpoint to determine an error. The PLC corrective output signal may be 4–20mA, 0–5Vdc, or another signal whose value is relative to the amount of error, and the correction is applied in a manner to eliminate the error. To provide sufficient actuation forces, the 4–20mA or 0–5Vdc output signal is often converted to a 3–15 psi or a 0–30 psi pneumatic signal to position a valve actuator or a power cylinder. The current-to-pneumatic converter is referred to as an I/P converter, which is essentially a signal amplifier. Proportional-only control leaves offset, or a deviation from the setpoint after a process disturbance has taken place, because the corrective signal is generated only after observing that a deviation exists. If the system can tolerate some level variations and the response speed is satisfactory, then proportional-only control is adequate. To reduce offset, the gain or sensitivity of the proportional control can be increased. Gain is the amplification of the output-signal relative to the input-signal. Gain can only be increased within limits constrained by the system dynamics, and controls that are too sensitive result in instability or hunting. PID mathematical instructions can be programmed into the PLC to improve the control. The integral and derivative functions add behavior that removes offset and speeds the response. This topic is discussed in Chapter 2 on “Control Terminology and Theory.”
Transistors: Lite!
Published in John D. Cressler, Silicon Earth, 2017
Well then, what’s a person to do about all this loss? You guessed it, create another law! Cressler’s 3rd Law: “Gain is essential for implementing useful electrical systems.” What is “gain,” you say? Just what it says. To make larger. To grow. Yep, opposite of loss. In our case, we want to make either the voltage larger, or the current larger; or, at a deeper level, make the electric-field or magnetic-field vectors in an EM wave larger. THE unique property of transistors that makes them indispensable for the implementation of complex electrical systems is that they possess inherent gain. Push a time-varying voltage signal of magnitude Vin into a transistor and I get a larger time-varying voltage signal of magnitude Vout out of said transistor. We define the voltage gain (AV) to be AV = Vout/Vin. You could do the same thing with current (AI = Iout/Iin), or even power if I’m driving an electrical “load” (AP = Powerout/Powerin). Clearly, gain (or loss) is dimensionless, but electronics geeks often speak about gain in decibel (dB) units for convenience (refer to the “Measures of Gain and Loss: Decibels” sidebar for the origins of the dB).
Operational amplifiers
Published in John Bird, Electrical and Electronic Principles and Technology, 2017
The open-loop voltage gain of an op amp is not constant at all frequencies; because of capacitive effects it falls at high frequencies. Fig. 21.3 shows the gain/bandwidth characteristic of a 741 op amp. At frequencies below 10 Hz the gain is constant, but at higher frequencies the gain falls at a constant rate of 6 dB/octave (equivalent to a rate of 20 dB per decade) to 0 dB. The gain-bandwidth product for any amplifier is the linear voltage gain multiplied by the bandwidth at that gain. The value of frequency at which the open-loop gain has fallen to unity is called the transition frequency fTfT=closed-loop voltage gain×bandwidth In Fig. 21.3, fT = 106 Hz or 1 MHz; a gain of 20 dB (i.e. 20 log10 10) gives a 100 kHz bandwidth, whilst a gain of 80 dB (i.e. 20 log10 104) restricts the bandwidth to 100 Hz.
A bulk-driven, buffer-biased, gain-boosted amplifier for biomedical signal enhancement
Published in Cogent Engineering, 2019
Sarin Vijay Mythry, D. Jackuline Moni
Gain of an amplifier can be defined as the difference between input signal and output signal. It is the characteristics which say about to what extent an input signal is amplified at output. It is the ratio of output signal to input signal. The amplifier gain models are depicted in Figures 9 and 10. The designed BD amplifier using bulk-driven technique has achieved a high gain of value 81 dB, shown in Figure 11. To examine the reaction of CMRR due to DC offsets, the both inputs terminals are fastened and connected to same input signal, by placing a DC offset voltage as voltage source in between two inputs. The obtained CMRR is calculated manually which is greater than 110 dB.
Experimental investigation on a flapping beam with smart material actuation for underwater application
Published in Mechanics of Advanced Materials and Structures, 2021
Ganesh Govindarajan, R. Sharma
Arrangements for the calibration of displacement of the beam are shown in Figure 4. The dimensions of the active part of MFC actuators are 103 × 57 × 60 mm. The beam is excited using the MFC and it is connected to an amplifier and the frequency is varied, while the strain gauge measured the response of beam and stored it on PC. The thrust is measured using the strain gauge, where the relationship between voltage and force from the strain gauge reading is linear [14]. The function of voltage amplifier which amplifies the input voltage and the gain is the relationship that exists between the two signals, that is, one measured at the output and the other measured at the input.