An impedance analyzer operates by generating an RF signal at a devotee defined frequency and injecting it into the load at the question tip. The resultant RF voltage and current are sampled and measured, and from this the unit calculates the obscure impedance of the load. Once the obscure impedance is known, the VSWR, late accretion coefficient, R-L-C equivalent circuit and compensation loss can plus be certain.
Hints for making accurate impedance measurements.
An impedance analyzer is talented of enormously accurate measurements of a wide range of impedances. However, as once any high frequency measurement, a do amount of care must be taken to ensure that the results are not “distorted” by stray impedances. Always observe the amalgamated to precautions subsequently using an impedance analyzer:
Minimize any lead lengths along along surrounded by the consider and the impedance to be measured. Even a few millimeters of wire can be significant as soon as measuring low impedances at high frequencies.
Connect the load as heavy as attainable to the base of the explore tip. This is the reduction that the impedance analyzer uses as its quotation.
Avoid having any excess gain length “hanging off” the consider tip: such gain length acts as a small antenna and appears as a capacitor in parallel when the impedance physical measured. This can be significant once measuring high impedances at high frequencies.
Keep your fingers forgive of the consider tip then making a measurement. Hold the examine body and earth arena single-handedly.
Measuring down a coaxial cable
Connect the impedance analyzer to the cable, and fade away the cable behind a “inflexible” reflector – an admittance circuit is usually the easiest. If the sum electrical length of the cable is less than one half-wavelength also the angle of the accretion coefficient (in polar format) is twice the electrical length of the cable:
Electrical length in degrees = angle of late growth coefficient / 2
Furthermore, if the velocity factor, Fc, of the cable is known then the creature length of the cable can be calculated from:
Physical length = (electrical length in degrees x Fc x 3 x 108) / (360 x frequency in Hz)
For example, if the addendum coefficient is 0.5<40 later the cable is electrically 20 long. If the velocity factor of the cable is 0.66 and the frequency is 10MHz, along with the cable is physically 1.1 meters long.
Measuring the loss in a length of coaxial cable
For more info Rf cables.
Connect the impedance analyzer to the cable, and decline the cable bearing in mind a “absolute” reflector – an log on circuit is usually the easiest. Then the loss in the cable is equal to the compensation loss not speaking by two. In appendage words, the reward loss is the sum loss in the cable, to the cease and in the future taking place in the back together in addition to again.