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9: Electrical Instrumentation Signals
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9.1: Analog and Digital Signals
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A signal is any kind of physical quantity that conveys information. An analog signal is a kind of signal that is continuously variable, as opposed to having a limited number of steps along its range (called digital). Both analog and digital signals find application in modern electronics.
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9.2: Voltage Signal Systems
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DC voltage can be used as an analog signal to relay information from one location to another. A major disadvantage of voltage signaling is the possibility that the voltage at the indicator (voltmeter) will be less than the voltage at the signal source, due to line resistance and indicator current draw. This drop in voltage along the conductor length constitutes a measurement error from transmitter to indicator.
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9.3: Current Signal Systems
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9.4: Tachogenerators
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9.5: Thermocouples
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9.6: pH Measurement
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9.7: Strain Gauges
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If a strip of conductive metal is stretched, it will become skinnier and longer, both changes resulting in an increase of electrical resistance end-to-end. Conversely, if a strip of conductive metal is placed under compressive force (without buckling), it will broaden and shorten. If these stresses are kept within the elastic limit of the metal strip (so that the strip does not permanently deform), the strip can be used as a measuring element for physical force, the amount of applied force infer