Differential probes measure the difference in signal level between any two measurement points. In contrast, a single-ended probe measures the difference between a single point and ground potential. Differential probes are especially popular for measuring high-frequency signals or signals of very low amplitude (i.e. approaching the noise floor). Differential probes require an differential amplifier to convert the difference between the two signals into a voltage that can be sent to the (single-ended) oscilloscope input.