The probe is the part of the spectrometer whose role is to transmit rf pulses to the sample via coils and using the same coils to detect the FID. To do this effectively the electrical properties of the coil circuitry must be optimised for each sample. This is known as tuning the probe. Tuning is actually two process, tuning and matching. Tuning aligns the coil to the correct radio frequency of the relevant nucleus. This involves changing variable capacitors within the probe circuits. The matching is changed to match the impedance (resistance to the current) of the coil and sample combination with the transmitter and receiver coil. The correct frequency and impedance will vary dependent on electrical properties of the sample. Tuning on Bruker systems is either done manually on the tuning rods on the probe and visualised via the “wobb” command or remotely using the “atma” command from topspin.