Sensors, Signals, and Systems

A sensor is often defined as a device that receives and responds to a signal or stimulus. This definition is broad. In fact, it is so broad that it covers almost everything from a human eye to a trigger in a pistol. Consider the level-control system. The operator adjusts the level of fluid in the tank by manipulating its valve. Variations in the inlet flow rate, temperature changes (these would alter the fluid’s viscosity and, consequently, the flow rate through the valve), and similar disturbances must be compensated for by the operator.Without control, the tank is likely to flood, or run dry. To act appropriately, the operator must obtain information about the level of fluid in the tank on a timely basis. In this example, the information is perceived by the sensor, which consists of two main parts: the sight tube on the tank and the operator’s eye, which generates an electric response in the optic nerve. The sight tube by itself is not a sensor, and in this particular control system, the eye is not a sensor either. Only the combination of these two components makes a narrow-purpose sensor (detector), which is selectively sensitive to the fluid level. If a sight tube is designed properly, it will very quickly reflect variations in the level, and it is said that the sensor has a fast speed response. If the internal diameter of the tube is too small for a given fluid viscosity, the level in the tube may lag behind the level in the tank. Then, we have to consider a phase characteristic of such a sensor. In some cases, the lag may be quite acceptable, whereas in other cases, a better sight tube design would be required. Hence, the sensor’s performance must be assessed only as a part of a data acquisition system.
This world is divided into natural and man-made objects. The natural sensors, like those found in living organisms, usually respond with signals, having an electrochemical character; that is, their physical nature is based on ion transport, like in the nerve fibers (such as an optic nerve in the fluid tank operator). In man-made devices,information is also transmitted and processed in electrical form—however, through the transport of electrons. Sensors that are used in artificial systems must speak the same language as the devices with which they are interfaced. This language is electrical in its nature and a man-made sensor should be capable of responding with signals where information is carried by displacement of electrons, rather than ions.1 Thus, it should be possible to connect a sensor to an electronic system through electrical wires, rather than through an electrochemical solution or a nerve fiber. Hence, in this book, we use a somewhat narrower definition of sensors, which may be phrased as A sensor is a device that receives a stimulus and responds with an electrical signal.

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Temperature Sensor

Temperature is the most often-measured environmental quantity. This might be expected since most physical, electronic, chemical, mechanical and biological systems are affected by temperature. Some processes work well only within a narrow range of temperatures; certain chemical reactions, biological processes, and even electronic circuits perform best within limited temperature ranges. When these processes need to be optimized, control systems that keep temperature within specified limits are often used. Temperature sensors provide inputs to those control systems.
Many electronic components can be damaged by exposure to high temperatures, and some can be damaged by exposure to low temperatures. Semiconductor devices and LCDs (Liquid Crystal Displays) are examples of commonly- used components that can be damage by temperature extremes. When temperature limits are exceeded, action must be taken to protect the system. In these systems, temperature sensing helps enhance reliability.
One example of such a system is a personal computer. The computer’s motherboard and hard disk drive generate a great deal of heat. The internal fan helps cool the system, but if the fan fails, or if airflow is blocked, system components could be permanently damaged. By sensing the temperature inside the computer’s case, high temperature conditions can be detected and actions can be taken to reduce system temperature, or even shut the system down to avert catastrophe. Other applications simply require temperature data so that temperatures effect on a process may be accounted for. Examples are battery chargers (batteries’ charge capacities vary with temperature and cell temperature can help determine the optimum point at which to terminate fast charging), crystal oscillators (oscillation frequency varies with temperature) and LCDs (contrast is temperature-dependent and can be compensated if the temperature is known).


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Cara Cepat Menyusun Skripsi

Menurut Kamus Besar Bahasa Indonesia (KBBI), skripsi diartikan sebagai karangan ilmiah yang diwajibkan sebagai bagian dari persyaratan pendidikan akademis. Buat sebagian mahasiswa, skripsi adalah sesuatu yang lumrah. Tetapi buat sebagian mahasiswa yang lain, skripsi bisa jadi momok yang terus menghantui dan menjadi mimpi buruk. Banyak juga yang berujar “lebih baik sakit gigi daripada bikin skripsi”.
Saya juga sering mendapat kiriman pertanyaan tentang bagaimana menyusun skripsi dengan baik dan benar. Ada juga beberapa yang menanyakan masalah teknis tertentu dengan skripsinya. Karena keterbatasan waktu, lebih baik saya jawab saja secara berjamaah di sini. Sekalian supaya bisa disimak oleh audiens yang lain.
Karena target pembacanya cukup luas dan tidak spesifik, maka tulisan ini akan lebih memaparkan tentang konsep dan prinsip dasar. Tulisan ini tidak akan menjelaskan terlalu jauh tentang aspek teknis skripsi/penelitian. Jadi, jangan menanyakan saya soal cara menyiasati internal validity, tips meningkatakan response rate, cara-cara dalam pengujian statistik, bagaimana melakukan interpretasi hasil, dan seterusnya. Itu adalah tugas pembimbing Anda. Bukan tugas saya.

Apa itu Skripsi
Saya yakin (hampir) semua orang sudah tahu apa itu skripsi. Seperti sudah dituliskan di atas, skripsi adalah salah satu syarat yang harus dipenuhi sebagai bagian untuk mendapatkan gelar sarjana (S1). Skripsi inilah yang juga menjadi salah satu pembeda antara jenjang pendidikan sarjana (S1) dan diploma (D3).
Ada beberapa syarat yang musti dipenuhi sebelum seorang mahasiswa bisa menulis skripsi. Tiap universitas/fakultas memang mempunyai kebijakan tersendiri, tetapi umumnya persyaratan yang harus dipenuhi hampir sama. Misalnya, mahasiswa harus sudah memenuhi sejumlah SKS, tidak boleh ada nilai D atau E, IP Kumulatif semester tersebut minimal 2.00, dan seterusnya. Anda mungkin saat ini belum “berhak” untuk menulis skripsi, akan tetapi tidak ada salahnya untuk mempersiapkan segalanya sejak awal.
Skripsi tersebut akan ditulis dan direvisi hingga mendapat persetujuan dosen pembimbing. Setelah itu, Anda harus mempertahankan skripsi Anda di hadapan penguji dalam ujian skripsi nantinya. Nilai Anda bisa bervariasi, dan terkadang, bisa saja Anda harus mengulang skripsi Anda (tidak lulus).
Skripsi juga berbeda dari tesis (S2) dan disertasi (S3). Untuk disertasi, mahasiswa S3 memang diharuskan untuk menemukan dan menjelaskan teori baru. Sementara untuk tesis, mahasiswa bisa menemukan teori baru atau memverikasi teori yang sudah ada dan menjelaskan dengan teori yang sudah ada. Sementara untuk mahasiswa S1, skripsi adalah “belajar meneliti”.
Jadi, skripsi memang perlu disiapkan secara serius. Akan tetapi, juga nggak perlu disikapi sebagai mimpi buruk atau beban yang maha berat.

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