Selasa, 28 Juni 2011

Data Terminal Equipment

Digital delay generators produce pulses at precise, programmed intervals to trigger devices under test. They are also used for gating, timing, triggering, and syncing. Basic digital delay generators are single-channel devices. More complex products with multiple channels are also available. Both types are similar to pulse generators, but have a much finer timing resolution and a much lower time delay and width-jitter. Sophisticated devices that combine the functions of digital delay generators and pulse generators may provide independent amplitude polarity and level control for each output. Some digital delay generators are used to produce edges to trigger devices. Others provide precise delays and width for grating.

Selecting digital delay generators requires an analysis of product specifications such as timing delays and widths. Percent accuracy, time base, root mean square (RMS) jitter, and trigger mode are also important considerations. There are six choices for trigger mode: burst, continuous, external trigger, external gate, duty cycle, and single shot. With burst mode, any channel may provide a burst of pulses at the internal rate, and the number of pulses may vary by channel. Duty-cycle digital delay generators set timing events at ON for M pulses and OFF for N pulses. Devices with an external trigger or external gate trigger-mode carry parameters such as rate, insertion delay, threshold, trigger slope (rising or falling edge), and impedance. Single-shot digital delay generators may have a pushbutton that provides a single trigger.

Many digital delay generators include a computer interface with an RS232, GPIB, USB or Ethernet connection. RS232 is a serial interface between data terminal equipment (DTE) and data communications equipment (DCE) that uses a binary data interchange. The general-purpose interface bus (GPIB) is designed to connect computers, peripherals and laboratory instruments so that data and control information can pass between them. Universal serial bus (USB) is a 4-wire, 12-Mbps serial bus for low-to-medium speed peripheral device connections. Ethernet is a local area network (LAN) protocol that uses a bus or star typology and supports data transfer rates of 10 Mbps. Digital delay generators that use other types of computer interfaces are also available.

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