Zero position (technology)
Zero position refers to technical elements that are in a defined starting position.
Basics
Many technical elements do not work with absolute values, but with relative ones . An example of this is the steering of a car. Without a comparison , i.e. the comparison of the setpoint value Auto drives straight ahead with the actual value Auto drives to the left , the driver cannot recognize the position of the steering in a stationary vehicle. The same applies to many light switches in daily life: the position of the light switch alone does not tell whether the light is on or off. Only the visual comparison delivers the actual value. After switching the light switch ( test sequence) we also know whether the light switch was really in the starting position or whether the light is simply broken.
Another problem occurs with optical gauges: the parallax error . The pointer of the instrument slides over the scale with a small distance . Depending on the perspective of the observer, the reading on the scale is different, although the pointer is always in the same position.
Applications
Whenever absolute information is not available, it is advisable to carry out a zero adjustment when using technical operating, display, control or measuring devices . To do this, the system is set to zero and the results are checked. If necessary, adjustments are made until the setpoint and actual value match.
This procedure is often even explicitly prescribed, e.g. B. in the cockpit of an aircraft during take-off preparations. All control elements must be brought to their zero position and the resulting displays must confirm this. For example, the altimeter (height measuring device) is set to the height of the runway.
A zero setting prescribed in Germany that we encounter very often is the tare setting in weighing technology . When we buy fresh products at the sausage or cheese counter, we don't want to pay for the packaging. Therefore, the balance must be set to zero with the packaging paper on top. This is the only way to ensure that only the goods are actually weighed. Without the packaging on top, such a scale must have a negative display.
We also encounter this procedure in IT. A hard disk or floppy disk drive moves the read / write head to a defined zero position after switching on. A contact or a light barrier is attached there so that the control electronics recognize that the zero position has been reached. Only from this moment on does the control system know where the head is at all times (if it is not moved manually).
A special zero setting is required in electronic color imaging processes. The perception of color depends on many factors ( see also color temperature ). An absolute color determination by technical means is very expensive and time-consuming. That is why electronic cameras and cameras know the white balance . Here a template in the color white is recorded and the electronics accept this as a zero position. All other color values are dependent on this white balance.