User Manual

www.id-innovations.com
14
ID-2/12/20 LA Series Datasheet X1
11.04.2013
14. Fine Tuning the ID-2LA
We recommend using an oscilloscope for fine-tuning. Connect the oscilloscope to observe the
125kHz AC voltage across the coil. Get a sizeable piece of ferrite and bring it up to the antenna loop.
If the voltage increases then more inductance is required. If the voltage decreases as the ferrite is
brought up to the antenna then the inductance is too great. If no ferrite is available then a piece of
aluminium sheet may be used for testing in a slightly different way. Opposing currents will flow in
the aluminium and it will act as a negative inductance. If the 125kH AC voltage increases as the
aluminium sheet approaches the antenna then the inductance is too high. Note it may be possible
that the voltage will first maximize then decrease. This means that the module is near optimum
tuning. When using ferrite for test then it implies that the coil is a little under value and when using
aluminium sheet it implies the coil is a little over value.