| 摘要 |
<p>A track and hold system for use with a test instrument such as a multimeter includes an input circuit, a buffer amplifier, a storage device such as a capacitor, an output amplifier, an output circuit, a detector for detecting a pulse on a signal passing from the input to the output, and a switch responsive to the detector for isolating the storage device from the input circuit but not the output circuit for a predetermined period. The system also includes a timer responsive to the detector to provide an isolation command to the switch for the predetermined period. Further, the system includes a delay circuit, responsive to the detector, for interposing a delay of variable duration prior to activating the timer. In a preferred embodiment, where the system is used in conjunction with a multimeter having a "hold" circuit which directs the meter to display the last-measured signal, an output is provided to the hold input of the meter directing the meter to "hold" for predetermined periods whenever the switch opens or closes. The "hold" output circuit is also used to provide indefinite retention of a reading and trigger lockout for the detector circuitry.</p> |
