A test probe and use of a test probe for measuring a waveform applied to a device under test

A test probe 100 for measuring a waveform applied to a device under test. The device may be a Field Asymmetric Ion Mobility Spectrometer (FAIMS). The probe comprises a probe body 101, optionally made of conductive metal, first and second signal lines 131, 133, and an electrically insulating spacer 135, 137. A first and second pin 103, 105 are supported, in electrical isolation from each other, by the spacer, and connected electrically to the first and second signal lines respectively. The spacer maintains the two pins at a fixed spatial separation relative to each other and in electrical isolation from the probe body. A further third ground pin 107 may be electrically connected to the body and isolated from the first and second pins. The signal lines may include attenuation resistors and/or variable capacitors (figure 3).