MEASUREMENTS 59 MEGACYCLE METER
Instrukcja Obsługi

It is only necessary to connect the inductor to be measured to the standard capacitor with the shortest possible leads wd manure the resultant resonant Srequency with the Model 5 9 as a grid d i p meter. Then the actual total Circuit inductance can be read Srm! t bchart OS Figure 14. . For maximum accuracy the inductor should be replaced. with a short copper strap (about 1/2 inch
'

wide,) and the new resonant Srequency or this combination determined with the Model 59. Then rind the inductance OS this latter combination from the chart OS Figure 1 4 and subtract this value Srom that: previously measured. he dirserence IS the true inductance of the inductor. Since the presence of shields, tuning slugs, etc. may seriously a r m t the value or an inductor which is to be measured, it lpay be necessary to leave the coil in place tor msasuremsnt. In this case, it will.be necessary to disconnect any tuning capacitor, tubeg,.and other capacitors associated With the coil to be measured, besore connecting the standard capacitor across the inductor. c. Measurement OS Mutual Inductance: Mutual inductance OS two coils can be meacoils in series aldsured by Sirst connecting the ing and measuring the resultant inductance as described above in Section V(b), and then connecting the two coils in series bucking and again measuring the resultant inductance. The disterence in inductance divided by rour is the mutual lnductance. * Figure 15 outlines the above procedure step by step. The use or the ~ o d e l59 permits mutual inductance measurements to be made near the actual operating Srequencies. In some circuits this may be or considerable advantage over lower Srequency measurements. Lower v a l u ~ sOS mutual inductance can be measured with the Model 59 than those possible on most low Srequency bridges.

C8

kd
4J l

nearure reronant frequency, fl, with the nodel 59. (Pick Ca to resonate near desired operating vfrequency to mearure U e c t i e mutual inductance : to mearurr aua mutual inductance, Cr large compared to dirtrlbuted capacitance of L1 and L2) Next mearure resonant froquency, 12, with colla rererred ar rhown.

After measuring fl and fa as above and calculating p1 from the above equation, the coefficient of coupling can be determinedr first mearure the self indu tance of L and L2 with the 59 and a ruitable standard capaciior; then for the direct Inductively coupled care

K:n

JGz

Thin method can also be used to mearure the effective mutual inductance of a pair of link coupled coils:

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For the link coupled caee
IS

-

lbrr .
k f . ) (L2

%ff*)

4h t

This equation assumes that the mutual inductances between each link coil and its tuned circuit are equal.

Figure 15 MEASUREMENT OF MUTUAL INDUCTANCE

*Henncp, "The Radlo En lneerlng Handbook", Pace 97.

20.