The emerging field of vacuum microelectronics has many promising applications including flat-panel displays, microwave devices, and ionization sources. The technology is based on arrays of microfabricated micrometer-scaled gated field emitters. Applications are currently limited by unacceptable reliability due primarily to failures of individual field emitters. The failure of an individual emitter produces a characteristic electrical pulse. A circuit is used to monitor and count these pulses. The technique provides a powerful tool for exploration of stable operating regimes for vacuum microelectronic devices and may be useful in other areas in which vacuum discharges must be monitored.