What is potentiometer taper? Potentiometer taper is the relation between the position and the resistance of a pot. In the majority of variable resistors available this is a linear relationship, meaning that the relative position is equal to the resistance ratio. For example when the potmeter is at the middle position, the output voltage is half of the full voltage over the potentiometer. For some applications and especially audio volume control, non-linear, logarithmic tapers are used. Definition Taper is the relation between the position of the potentiometer and the resistance ratio. Types The simple linear taper is the most common form, when we plot the position against the resistance ratio we can visualize the different position-resistance relations. The graph below shows the most used tapers. The first and last few percents of travel are often only mechanical with no change in resistance. The region between 5 and 95% where the electrical resistance changes is called the electrical travel. The available travel for rotary pots is often denoted in degrees, a mechanical travel of 300° combined with a electrical travel of 270° is common. Audio taper The most used non-linear taper is the logarithmic (log) or audio taper. This is mainly used for audio volume control, to obtain a more natural ‘linear’ perception in sound intensity change when you adjust the volume. Because the human ear is sensitive to sound intensity in a logarithmic fashion, at low sound intensities a small change in intensity is perceived as a big change in loudness, while at high intensities a large change is required for the same change in perceived loudness. To compensate for the ears logarithmic behavior, audio taper pots were developed. While it is called logarithmic, it is actually an exponential curve (the opposite of the logarithmic behavior of the human ear). [… read more]

What is a variable resistor? A variable resistor is a resistor of which the electric resistance value can be adjusted. A variable resistor is in essence an electro-mechanical transducer and normally works by sliding a contact (wiper) over a resistive element. When a variable resistor is used as a potential divider by using 3 terminals it is called a potentiometer. When only two terminals are used, it functions as a variable resistance and is called a rheostat. Electronically controlled variable resistors exist, which can be controlled electronically instead of by mechanical action. These resistors are called digital potentiometers. Variable resistor definition A resistor of which the ohmic resistance value can be adjusted. Either mechanically (potentiometer, rheostat) or electronically (digital potentiometer). Types of variable resistors Potentiometer The potentiometer is the most common variable resistor. It functions as a potential divider and is used to generate a voltage signal depending on the position of the potentiometer. This signal can be used for a very wide variety of applications including: Amplifier gain control(audio volume), measurement of distance or angles, tuning of circuits and much more. When variable resistors are used to tune or calibrate a circuit or application, trimmer potentiometers or trimpots are used, this are mostly small potentiometers mounted on the circuit board, which can be adjusted using a screwdriver. Rheostat Rheostats are very similar in construction to potentiometers, but are not used as a potential divider, but as a variable resistance. They use only 2 terminals instead of the 3 terminals potentiometers use. One connection is made at one end of the resistive element, the other at the wiper of the variable resistor. In the past rheostats were  used as power control devices in series with the load, such as a light bulb. Nowadays rheostats are not used as power control anymore [… read more]