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114 lines
3.9 KiB
ReStructuredText
114 lines
3.9 KiB
ReStructuredText
Signals and Units
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=================
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Many commands allow you to specify arguments in terms of well-known physical quantities. This page gives an overview of each quantity and its unit.
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.. _time:
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time: ms
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---------
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All time and duration values are measured in milliseconds (ms).
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For example, the duration of motion with :meth:`run_time <.ev3devices.Motor.run_time>`, the duration of :func:`wait <.tools.wait>`, or the time values returned by the :class:`StopWatch <.tools.StopWatch>` are specified in milliseconds.
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.. _angle:
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angle: deg
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-----------
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All angles are measured in degrees (deg). One full rotation corresponds to 360 degrees.
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For example, the angle values of a :meth:`Motor <.ev3devices.Motor.angle>` or the :meth:`GyroSensor <.ev3devices.GyroSensor.angle>` are expressed in degrees.
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.. _speed:
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rotational speed: deg/s
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-----------------------
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Rotational speed, or *angular velocity* describes how fast something rotates, expressed as the number of degrees per second (deg/s).
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For example, the rotational speed values of a :meth:`Motor <.ev3devices.Motor.speed>` or the :meth:`GyroSensor <.ev3devices.GyroSensor.speed>` are expressed in degrees per second.
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While we recommend to work with degrees per second in your programs, you can use the following table to convert between commonly used units.
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+-----------+-------+-----------+
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| | deg/s | rpm |
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+-----------+-------+-----------+
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| 1 deg/s = | 1 | 1/6=0.167 |
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+-----------+-------+-----------+
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| 1 rpm = | 6 | 1 |
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+-----------+-------+-----------+
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.. _distance:
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distance: mm
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-------------
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Distances are expressed in millimeters (mm) whenever possible.
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For example, the distance value of the :meth:`UltrasonicSensor <.ev3devices.UltrasonicSensor.distance>` is measured in millimeters.
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While we recommend to work with millimeters in your programs, you can use the following table to convert between commonly used units.
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+---------+------+-----+--------+
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| | mm | cm | inch |
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+---------+------+-----+--------+
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| 1 mm = | 1 | 0.1 | 0.0394 |
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+---------+------+-----+--------+
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| 1 cm = | 10 | 1 | 0.394 |
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+---------+------+-----+--------+
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| 1 inch =| 25.4 | 2.54| 1 |
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+---------+------+-----+--------+
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.. _dimension:
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dimension: mm
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-------------
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Dimensions are expressed in millimeters (mm) whenever possible, just like distances.
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For example, the diameter of a wheel is measured in millimeters.
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.. _relativedistance:
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relative distance: %
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---------------------
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Some distance measurements do not provide an accurate value with a specific unit, but they range from very close (0%) to very far (100%). These are referred to as relative distances.
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For example, the distance value of the :meth:`InfraredSensor <.ev3devices.InfraredSensor.distance>` is a relative distance.
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.. _travelspeed:
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speed: mm/s
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------------
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Linear speeds are expressed as millimeters per second (mm/s).
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For example, the speed of a robotic vehicle is expressed in mm/s.
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.. _acceleration:
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rotational acceleration: deg/s/s
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--------------------------------
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Rotational acceleration, or *angular acceleration* describes how fast the rotational speed changes. This is expressed as the change of the number of degrees per second, during one second (deg/s/s). This is also commonly written as :math:`deg/s^2`.
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For example, you can adjust the rotational acceleration setting of a :meth:`Motor <.ev3devices.Motor.set_run_settings>` to change how smoothly or how quickly a motor reaches the constant speed set point.
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.. _percentage:
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percentage: %
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Some signals do not have specific units but range from a minimum (0%) to a maximum (100%). A specific type of percentages are :ref:`relative distances <relativedistance>`.
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For example, the sound :meth:`volume <.ev3brick.sound.beep>` range from 0% to 100%.
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.. _frequency:
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frequency: Hz
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Sound frequencies are expressed in Herz (Hz).
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For example, you can choose the frequency of a :meth:`beep <.ev3brick.sound.beep>` to change the pitch.
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