Difference between revisions of "Machine Unit"

From TheAnalogThing
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[[File:Overload.svg|thumb|350px|A cartoon showing the evolution of some quantity (blue) within the machine units (green shaded area), going into overload (red shaded area). As soon as a value reaches overload, it is ''clipped'', the LED goes on and the furthermore computation is most likely ''wrong''! There is a small ''tolerance'' gap ov 2V above the machine units.]]
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THE ANALOG THING's '''machine unit''' is the voltage interval in which the device represents values. This interval is -10V to +10V. THAT users are expected to scale their programs to fit into the real number interval <code>[-1,+1]</code>, which THAT represents in its -10V to +10V machine unit.
  
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'''Machine units''' are the conventions how to represent numbers on [[analog computer]]s such as [[The Analog Thing]] (THAT). In digital context, these are typically called ''logic levels''.
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To understand the need for these scale conversions, consider that users want to model values at any scale while THAT is limited to its modest physical boundaries. Modeling the dynamics of the global human population (currently around 7.9 Billion) should obviously not require 7.9 Billion Volts. The population value needs to be scaled. As a convention, analog computer models are scaled to the model unit <code>[-1,+1]</code>. The global population might, for example, be represented as 0.79. In its machine unit, THAT would then represent this value as 7.9V.  
  
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THAT works with ''logical one'' represented by +10V and ''logical minus one'' represented by -10V. It is helpful to thing in all quantities being bracketed within the real number interval <code>[-1,+1]</code>. In electrical engineering, this is called ''bounded in bounded out'' systems, as any computation has to produce results within this domain in order to be meaningful on an analog computer. These machine units are ''bipolar'', this is in contrast to ''unipolar'' units such as 0V for logical zero and +5V for logical one in the digital TTL logic system.
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Good model scaling uses as much of the machine unit as possible ​without exceeding it. You understand the reasons for this if you understand that weighing cooking ingredients on scales intended for trucks or weighing a truck on a kitchen scales would not give very useful results.
  
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== Levels for output ==
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Using the -10V to +10V range as the machine unit is an engineering choice and a convention. It happens to be a very good choice because it allows for easy conversions in the decimal number system, it can be handled very precisely using affordable electronic components, and it is perfectly safe for humans.
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When it comes to [[output]] which can be displayed on [[oscilloscope]]s, level shifting may apply. For instance, the [[Soundcard]] output operates with roughly ±1V.
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When any value in a program exceeds the machine unit, the red <code>OL</overload> (overload) LED lights up. This is not dangerous for the device. However, in this condition, THAT will likely "clip" any excess voltages and the values in question will not be computationally correct.
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Output signals available via the RCA (or "chinch") jacks on the device's back side are not in the machine unit. Instead, they are attenuated to smaller audio signal levels so they can conveniently be read into software [[oscilloscope]]s via sound card interfaces.
  
 
[[Category:Hardware]]
 
[[Category:Hardware]]
 
[[Category:Fundamentals]]
 
[[Category:Fundamentals]]

Revision as of 07:43, 27 August 2021

THE ANALOG THING's machine unit is the voltage interval in which the device represents values. This interval is -10V to +10V. THAT users are expected to scale their programs to fit into the real number interval [-1,+1], which THAT represents in its -10V to +10V machine unit.

To understand the need for these scale conversions, consider that users want to model values at any scale while THAT is limited to its modest physical boundaries. Modeling the dynamics of the global human population (currently around 7.9 Billion) should obviously not require 7.9 Billion Volts. The population value needs to be scaled. As a convention, analog computer models are scaled to the model unit [-1,+1]. The global population might, for example, be represented as 0.79. In its machine unit, THAT would then represent this value as 7.9V.

Good model scaling uses as much of the machine unit as possible ​without exceeding it. You understand the reasons for this if you understand that weighing cooking ingredients on scales intended for trucks or weighing a truck on a kitchen scales would not give very useful results.

Using the -10V to +10V range as the machine unit is an engineering choice and a convention. It happens to be a very good choice because it allows for easy conversions in the decimal number system, it can be handled very precisely using affordable electronic components, and it is perfectly safe for humans.

When any value in a program exceeds the machine unit, the red OL</overload> (overload) LED lights up. This is not dangerous for the device. However, in this condition, THAT will likely "clip" any excess voltages and the values in question will not be computationally correct.

Output signals available via the RCA (or "chinch") jacks on the device's back side are not in the machine unit. Instead, they are attenuated to smaller audio signal levels so they can conveniently be read into software oscilloscopes via sound card interfaces.

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