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I have been trying to figure out a explanation to this question, can someone explain this ?

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    \$\begingroup\$ Because it is intended to go to some electrical input. \$\endgroup\$ – Eugene Sh. Aug 17 '18 at 19:30
  • \$\begingroup\$ The entire point of a transducer is to convert a physical parameter to an electrical one; or the opposite of that. Sensors are transducers. Speakers are transducers. Microphones are transducers. etc. \$\endgroup\$ – jonk Aug 17 '18 at 19:33
  • \$\begingroup\$ Add the fact that the electrical signal can be displayed remotely... \$\endgroup\$ – Solar Mike Aug 17 '18 at 19:42
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    \$\begingroup\$ Because we use electrical systems to connect them to, so we want an output signal electrical systems understand (and those are: electrical signals). \$\endgroup\$ – L. Heinrichs Aug 17 '18 at 19:47
  • \$\begingroup\$ Imagine sensors without output data. "Hey guys! Guess what I just saw/felt/heard?" Who cares? It's not like we do anything with your observations.... \$\endgroup\$ – KingDuken Aug 17 '18 at 20:13
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Why do most sensors have an electrical output, regardless of the physical nature of the variable being measured?

Electrical control systems have the following advantages over alternatives such as mechanical, pneumatic, hydraulic, etc.

  • Speed. Electrical control systems are fast.
  • Size. The control systems can be miniaturised.
  • Power. Electricity is readily available. No compressors or pumps are required.
  • Reliability. Electro-mechanical (relay) systems can have high reliability despite the moving parts. Solid-state (transistor, triac, etc.) can have far higher reliability as there are no moving parts.
  • Distance. Electrical signals can be transmitted long distances without significant loss.
  • Cost. Mechanical control systems require precision components which can be more expensive to manufacture and calibrate.
  • Versatility. Electrical systems are very versatile. Transducers are available to convert light, sound, pressure, force, strain, radioactivity, viscosity, temperature, velocity, etc., into electrical signals.

The last one is probably the most important. While, for example, pneumatic logic and control systems exist and have their benefits (explosive atmospheres, for example) it is difficult to imagine how a light to air pressure transducer is going to beat a light-dependent resistor. In other applications such as temperature control mechanical solutions - car coolant thermostat, for example - are more than adequate.

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That's easy- spirit of the time. Current technology is all about electronics. A hundred years ago it was different, Litmus for example hasn't electrical output :)

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    \$\begingroup\$ Or even 60 years ago it was pneumatic. The 4ma->20mA current loop signaling comes directly from pneumatic control systems of the early 20th century. \$\endgroup\$ – crasic Aug 17 '18 at 20:04
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    \$\begingroup\$ The canary was a sensor - used down a coal mine and when it fell of its perch it was time to evacuate +1 for spirit of the time. \$\endgroup\$ – Andy aka Aug 18 '18 at 10:07
  • \$\begingroup\$ Yeah, disposable biotech high end gas sensor! \$\endgroup\$ – Gregory Kornblum Aug 18 '18 at 10:18
  • \$\begingroup\$ Optical fibres are sometimes used when electricity is not possible. \$\endgroup\$ – KalleMP Aug 18 '18 at 10:36
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Sensors could press on or retract a pushrod.

With air-bearings, the wear factor would be excellent (long duration sensing).

But imaging the task of instrumenting a nuclear-test-site, with lots of crucial measurements having impulse-responses of nanoseconds or microseconds. The pushrod inertial serves as a low-pass-filter; the exploration of uranium at Los Alamos might still be underway, and USA might now be speaking German.

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  • \$\begingroup\$ A push rod is hardier against radiation than [today's typical] electronics, though. \$\endgroup\$ – Nick Alexeev Aug 18 '18 at 17:21
  • \$\begingroup\$ I occasionally wonder how humanity will develop those generational spacecraft, ready for 100,000 year voyages between the stars. Certainly the Air Conditioning systems will run through fan bearings every 100 years, thus 1,000 sets of A/C bearings must be placed in ship-stores, or bearing-manufacturing is one of the human skill sets places onboard. \$\endgroup\$ – analogsystemsrf Aug 20 '18 at 4:44

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