WB6DHWWB6DHW

PC-Based RLC Meter KitPC-Based RLC Meter Kit

Proposed Buildathon Project:Proposed Buildathon Project:– April 2011 Radio Play Days (16 Apr 2011)April 2011 Radio Play Days (16 Apr 2011)– Build simple $20 kit in one play day sessionBuild simple $20 kit in one play day session– Learn some electronics while we’re at itLearn some electronics while we’re at it– Minimal hand-holdingMinimal hand-holding– Have fun, tooHave fun, too

Kit:Kit:– Furnished by Dave Brainerd WB6DHWFurnished by Dave Brainerd WB6DHW– No toroids, no SMTNo toroids, no SMT– Measures R, L, and CMeasures R, L, and C– Easy build (25 components)Easy build (25 components)

ComponentsComponents

User-furnished partsUser-furnished partsTwo stereo M-M 1/8” cablesTwo stereo M-M 1/8” cablesHookup wireHookup wire2 alligator clips2 alligator clipsOne USB-A to USB-B cableOne USB-A to USB-B cable

RequirementsRequirements– PC with soundcard and free USB portPC with soundcard and free USB port

Soundcard MUST have Soundcard MUST have stereostereo input input USB just for 5V powerUSB just for 5V power

– Fairly accurate DMMFairly accurate DMM– (downloadable) Software(downloadable) Software– Soldering iron and solderSoldering iron and solder– Diagonal cutters and needle-nosed pliersDiagonal cutters and needle-nosed pliers– A (Pana)vise would be niceA (Pana)vise would be nice– User-furnished partsUser-furnished parts

Two stereo M-M 1/8” cablesTwo stereo M-M 1/8” cables Hookup wireHookup wire 2 alligator clips2 alligator clips One USB-A to USB-B cableOne USB-A to USB-B cable

Completed Completed Kit:Kit:

SchematicSchematic

Build StagesBuild StagesPower Supply Negative Power Supply Resistance Ladder

OpAmps & I/O Calibration

TheoryTheory– ApplyApply reference reference

signal to voltage signal to voltage dividerdivider

– MeasureMeasure reference and reference and output signalsoutput signals

– Calc Calc Unknown Unknown impedanceimpedance(ohms: R & X)(ohms: R & X)

Resistor Ladder SelectionResistor Ladder Selection

Rm L-From L-To C-From C-To

10 12.99 uH 12.99 mH 0.1299 uF 1299 uF

100 129.9 uH 129.9 mH 0.01299 uF 129.9 uF

1k 1.299 mH 1299 mH 1.29 nF 12.9 uF

10k 12.99 mH 12.99 H 1299 pF 1.29 uF

100k 129.9 mH 129.9 H 12.99 pF 0.129 uF

Rm XL_From XL_To Xc_From Xc_To

10 0.1 100 1k 0.1

100 1 1k 10k 1

1k 10 10k 100k 10

10k 100 100k 100k 100

100k 100k 1M 10M 1k

LFXCF

X

L

C

***2***2

1

the measurement of inductances and resistances calls for values of Rm that are proportional to the expected value of the component being measured; the value of Rm for capacitors is inversely proportional to the expected value

TheoryTheory–

– X is capacitive or inductive X is capacitive or inductive reactancereactance

– Voltage Divider consists of Voltage Divider consists of RRmm and and ZZ??

– VVrr = reference (AC) voltage, = reference (AC) voltage,VVx x = measured (AC) voltage= measured (AC) voltage

– Calc: Calc: ZxZx, Given:, Given:– VVrr

VVxx

RRmm

2X 2R?Z

MeasurementsMeasurements

ReferencesReferences– These slides: These slides:

http://www.wb5rvz.com/presentations/RLC_Buildathon.ppthttp://www.wb5rvz.com/presentations/RLC_Buildathon.ppt

– Build Notes: Build Notes: http://www.wb5rvz.com/rlc_meter/http://www.wb5rvz.com/rlc_meter/– Kit Resources: Kit Resources: http://wb6dhw.com/RLC_Meter.htmlhttp://wb6dhw.com/RLC_Meter.html

ArticlesArticles– QSTQST– QEXQEX

SoftwareSoftware PurchasePurchase: :

http://wb6dhw.com/For_Sale.html#RLC_Meterhttp://wb6dhw.com/For_Sale.html#RLC_Meter Any Questions???????????Any Questions???????????