Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives Magazine Sponsor RF Cafe Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Alliance Test Equipment Centric RF Empower RF ISOTEC Reactel RF Connector Technology San Francisco Circuits Anritsu Amplifier Solutions Anatech Electronics Axiom Test Equipment Conduct RF Copper Mountain Technologies Exodus Advanced Communications Innovative Power Products KR Filters LadyBug Technologies Rigol TotalTemp Technologies Werbel Microwave Windfreak Technologies Wireless Telecom Group Withwave RF Cafe Software Resources Vintage Magazines RF Cafe Software WhoIs entry for RF Cafe.com Thank you for visiting RF Cafe!
RF Cascade Workbook 2018 by RF Cafe

Exodus Advanced Communications Best in Class RF Amplifier SSPAs

ConductRF Phased Matched RF Cables - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low-priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel

Temwell Filters

Parallel Resistance Chart
October 1958 Radio-Electronics

October 1958 Radio-Electronics

October 1958 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

If you have ever placed a fixed resistor in parallel with a potentiometer to reduce the total resistance, then you are familiar with how you also convert a linear relationship of the wiper movement with resistance to one that is nonlinear. That is because the equation changes from Rtotal = Rx:potentiometer (where x is the potentiometer position) to Rtotal = (Rx:potentiometer * Rparallel) / (Rx:potentiometer + Rparallel). The graph of it looks like one of the curves in this chart. Since the total parallel resistance is always smaller than the lowest value of the two resistances, the greater the ratio of the two is, the more dominant the smaller resistance value becomes. That means as the potentiometer wiper approaches the minimum resistance end of its travel, the parallel resistor attached across it has virtually no effect.

Since parallel-connected inductors and series-connected capacitors scale in the same manner as parallel-connected resistors, this chart is useful for those circuits as well. Series-connected resistors and inductors, and parallel-connected capacitors are simply the sums of their individual values. Consequently, if you connect a fixed resistor in series with a potentiometer, the total resistance at any position of the potentiometer wiper will be the linear sum of the fixed resistor and the potentiometer resistance. Got that?

* Theoretically, x is a value from 0 to 1 that represents the relative position of the potentiometer wiper contact.

Parallel Resistance Chart

Parallel Resistance Chart, October 1958 Radio-Electronics - RF CafeBy Rudolph Wellsand

To use the chart locate R1 along the top scale and R2 on the left-hand scale. Find the point where they meet on a curve. Trace the curve to the RT scale and read the answer. For total values of parallel inductance and series capacitance use the scales at the bottom and right hand edges. To extend the ranges of the scales, either multiply or divide each value in every scale by 1,000.

 

 

Posted June 9, 2022
(updated from original post on 1/4/2015)

Temwell Filters
KR Electronics (RF Filters) - RF Cafe

TotalTemp Technologies (Thermal Platforms) - RF Cafe

Innovative Power Products Passive RF Products - RF Cafe