Conversion Value Signal Conditioning
a. Changing the signal level
The method is simple in signal conditioning circuit is to change the level or the value of the signals. The example often used is the reinforcement (amplifier) and attenuation (attenuate) voltage levels. In general, application of control systems with dc or low-frequency signals can be amplified easily. The important factor for choosing a series of reinforcement is the input impedance of the sensor output. In the control system, the signal is always describe the process variable (or output system) which will be compared with the value of the variable (reference value) to be processed by the controller. In some cases the frequency response in a series of reinforcement is very important to note, for example, the accelerometer sensor and an optical detector.
b. Linearization
In accordance with the previous explanation, that the maker of control systems have little choice of sensor output characteristics of the process variable. Often the relationship between the input and output of the sensor is not linear. Even approaching linearpun sensor can also be a problem when the measurement precision of a variable signal is required. Historically, analog circuits devoted to the use of linear signals.
For example, the estimated output of a sensor varies and is not linear with the process variable. Shown in Figure 9:23 (a). Linearization circuit made the block diagram shown in Figure 9:23 (b), the conditions are ideal, namely a linear relationship in the form of the sensor output voltage and process variables is obtained, as shown in Figure 2.23 (c). The circuit as it is difficult to design it and usually kerjanyadibatasi.Pendekatan area of modern surgery for this problem is to make ersebut linea signals as input from a computer and to form linearized using software. Virtually, many ketidaklinearan can be solved in this way with a fast modern computer processing in real time.
c. Conversion
Often the signal conditioner is used for converting from electrical quantities to electrical quantities one another. Most of the group sensor / transducer, shows the need to change the resistance with dynamic variables. In this case, should be provided the circuit is resistant to convert into a voltage signal (Volt) or current signals (Ampere). It usually can be met by the bridge circuit when the resistance change is small and / or the amplifier circuit (amplifier) with a variation of gain.
Important types of a conversion associated with standard process control of the transmitted signal in the form of a current of 4-20 mA level on the cable. This requires the conversion of resistance and voltage levels into the current required level at the end of the transmission of signals and for the conversion of current into a voltage turning on the receiving end of the signal sent. Surely signal transmission (signal transmission) to be used as the signal flow is not dependent on the varying loads.
By doing so, it is necessary perubah voltage to current and current to voltage changer. microcomputer control system requires the conversion of analog data into digital data (digital interfacing) by the integrated circuit. The circuit is called the Analog to Digital Converter (ADC). Analog signal conversion is usually necessary to adjust the analog signal is measured to fit into a digital signal that is required as input ADC.
For example, the ADC requires the input signal varies between 0 to 5 Volts, but the sensor provides a signal that varies between 30 to 80 mV. The signal converter circuit can be made to connect the sensor output to ADC input required.
d. Filters and Impedance Adjustment
There are two other joint signal conditioning is required, ie the filtering process (filtering) and adjustment of the impedance (impedance matching). Often the information signal that is often found in the world today ind ustri has a frequency of 60 Hz. The electric motor when at the start, causing pulse signals and other signals that are not desirable in any particular control system. In many cases, this requires the use of high-pass filter, low-pass filter or notch filter to reduce or eliminate such unwanted signals.
Examples of process filters which can be met by a passive filter is only by means of resistors, capacitors, and inductors, or active filter by using reinforcement and feedback (feedback). Impedance adjustment is an important element in the signal conditioning when the internal impedance of the sensor or transmission line impedance can cause errors (errors) in the measurement of dynamic variables. The circuit uses active and passive components used to hold the impedance adjustment.
e. Imposition concepts
One of the main concerns in analog signal conditioning is the imposition of a series by the other circuit. Here introduced the uncertainty of the amplitude of a signal voltage. If this voltage represents several process variables, then adaketidakpastian in the value of the variable.
Figure 2.23 The concept of imposition
Figure 2.23 Imposition Imposition concepts can be explained as follows. For example, the output from open circuit of some electronic components generate a voltage y y1 = V x, according to the image 2:23 (a).
