Technical data

590 Agilent N8201A Performance Downconverter Synthetic Instrument Module, 250 kHz to 26.5 GHz
28 Programming Fundamentals
• Read D characters, the resulting integer specifies the number of data bytes sent.
• Read the bytes into a real array.
For example, suppose the header is #512320.
• The first character/digit in the header (5) tells you how many additional digits there are
in the header.
• The 12320 means 12 thousand, 3 hundred, 20 data bytes follow the header.
• Divide this number of bytes by your current data format (bytes/data point), 8 for real,64.
For this example, there are 1540 data points in the block of data.
Avoid unnecessary use of *RST
Remember that while *RST does not change the current Mode, it presets all the
measurements and settings to their factory defaults. This forces you to reset your N8201A’s
measurement settings even if they use similar mode setup or measurement settings. See
“Minimize DUT/instrument setup changes" on page 590. (Also note that *RST may put the
instrument in single measurement/sweep for some modes.)
Put ADC Ranging in Bypass for FFT Measurements for N8201A
Setting ADC ranging to the Bypass mode can speed FFT measurements up by 10% to 50%.
(Use ADC:RANG NONE) Bypass allows triggered FFT measurements to occur at the
trigger time instead of following an autoranging time, so it can improve measurement
speed. It does, however, add additional noise degrading your signal to noise level, so it
should be used carefully.
Minimize DUT/instrument setup changes
• Some instrument setup parameters are common to multiple measurements. You should
look at your measurement process with an eye toward minimizing setup changes. If your
test process involves nested loops, make sure that the inner-most loop is the fastest.
Also, check if the loops could be nested in a different order to reduce the number of
parameter changes as you step through the test.
• Are you are using the measurements under the MEASURE key? Remember that if you
have already set your Meas Setup parameters for a measurement, and you want to
make another one of these measurements later, use READ:<meas>?. The
MEASure:<meas>?. command resets all the settings to the defaults, while READ
changes back to that measurement without changing the setup parameters from the
previous use.
• Are you are using the Measurements under the MEASURE key? Remember that Mode
Setup parameters remain constant across all the measurements in that mode (e.g.
center/channel frequency, amplitude, radio standard, input selection, trigger setup). You
don’t have to reinitialize them each time you change to a different measurement.