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Trim potentiometers

By EPCI Posted On 10.10.2019

Source: EPCI ABC of CLR online handbook article

The need for small, adjustable resistors created trim potentiometers. They lack the potentiometer shaft and are operated through an adjustment screw or a rotor. The setting needs to be maintained during handling and environmental influence. Thus, the contact pressure of the wiper is high. The setting stability is specified as a voltage change expressed in percent of input voltage. The first trimming potentiometers had a carbon track or a wirewound element. The carbon track potentiometers exist in a variety of designs, both for surface mount and hole mount, from the cheapest and most simple designs with a substrate of bakelite paper or the like and a sprayed suspension to conductive plastic on a ceramic substrate. The most predominant material, however, is cermet, not least due to the breaking into the market of SMD designs. (more…)

ABC of CLR Tutorial  / All Resistors  / Basic Concepts Resistors  / e-PassiveBlog  / Potentiometers  / Resistors  / Resistors ABC

Precision potentiometers type 1

By EPCI Posted On 10.10.2019

Source: EPCI ABC of CLR online handbook article

According to IEC precision potentiometers are classified as Type 1. They exist in both bushing mount styles and in servo applications. In the latter case high demands are made for rotational life and low torque. Such potentiometers are supplied with ball bearings. If they in addition are sealed against moisture this will influence the torque. The solution of such problems implies explicit requirement specifications and close cooperation with prospective manufacturers. For very severe environments there exist, among other things, oil-filled potentiometers. (more…)

ABC of CLR Tutorial  / All Resistors  / Basic Concepts Resistors  / e-PassiveBlog  / Potentiometers  / Resistors  / Resistors ABC

Potentiometers type 2

By EPCI Posted On 10.10.2019

Source: EPCI ABC of CLR Resistors article

R 4.2.1 Power potentiometers

Power potentiometers are as a rule wirewound. They are wound on a ceramic body and lack, due to heat dissipation concerns, encapsulation in casings or housings. Often they have a touch protection of silicone lacquer, cement or enamel and they are readily used as rheostats. If we turn the shaft of a rheostat towards zero resistance it is not unusual that the current burns off the last turns in the winding if the load impedance is low. Hence, the current in a rheostat must not exceed that of the rated power. (more…)