Avtech instruments with the -B suffix include a complete computer control interface. The -B suffix allows Avtech instruments to be remotely controlled by a computer via the General-Purpose Interface Bus (GPIB) or via a RS-232 serial port. The GPIB interface is IEEE 488.1 and IEEE 488.2 compliant. The instrument command set is based on the easy-to-understand industry-standard "Standard Commands for Programmable Instruments (SCPI)". Examples of typical commands are:
frequency 1.2 kHz
As shown, numeric values can be specified with units, or in scientific notation. The last example is a query command, which returns the current delay setting to the computer.
Instruments with the -B suffix normally share a common physical appearance and size (see the photos below). These instruments feature a keypad and a back-lit liquid crystal display on the front panel. All pulse parameters can be changed via the front panel or through the computer interface. The large display normally shows all key parameters (such as frequency, pulse width, delay, amplitude, offset, trigger mode, etc) simultaneously, for easy "at-a-glance" use. The front panel also has a "single pulse" button for manually triggering a single pulse. The MAIN and SYNC output connectors are on the front panel, and the EXT TRIG and GATE connectors are on the rear panel. (Note: The AV-151 and AV-153 series of function generators do not use the single-pulse or EXT TRIG modes.)
The interface contains memory to store up to four complete instrument setups. The operator can use the front panel or the computer interface to store a complete "snapshot" of all key instrument settings, and recall this setup at a later time. This simplifies the setup of frequently performed experiments.
The GPIB interface is useful when a user wishes to control several instruments from the computer. This approach requires a GPIB controller board in the user's computer. (National Instruments is the recommended source of controller boards.) A two meter GPIB cable is included with the -B instruments. The RS-232 interface is a lower-cost approach to remote instrument control, since most computers have at least one RS-232 serial port built-in. However, only one instrument can be attached to a RS-232 port at a time. Avtech instruments with the -B suffix have a female 25-pin RS-232 connector on the rear panel, and can be connected to a computer with a standard "straight-through" serial cable. (This cable can be purchased at most computer stores. Several variations are available due to the existence of several different types of RS-232 connectors on personal computers.)
The resolution of the timing parameters varies, but is always better than 0.15% of the current setting. (i.e. the setting can always be incremented or decremented by ±0.15% or less), with two exceptions. For the delay and pulse width at very low settings, resolution < 0.15% of (|PW or delay|+20ns). For frequencies between 0.1 Hz and 1 Hz, the resolution is <0.7%. The amplitude and offset parameters typically have a resolution of 0.03% of the full-scale setting. Accuracy is typically ±3%. Pulse width and delay RMS jitter for instruments with the -B suffix option is typically ±(35ps + 0.015% of PW or delay).
Low-cost units without GPIB control but with similar output pulse performance are available for most models (the -B suffix is replaced by a -C suffix).
LabView drivers are also available for many instruments, to allow easy integration into test systems.
Ethernet Port Optionally Available
The -VXI option adds a rear-panel Ethernet connector, allowing an instrument to be remotely controlled using the VXI-11.3, ssh (secure shell), telnet, and http (web) protocols. In particular, the VXI-11.3 features allows software like LabView to control an instrument using standard VISA communications drivers and network cabling, instead of using old-style GPIB cabling. Find out more about the -VXI option!