Model 2651A High Power System SourceMeter® Instrument Reference Manual
Section 2: General operation
2651A-901-01 Rev. A / March 2011
2-71
Digits
The display resolution of the measured reading depends upon the DIGITS setting. The DIGITS
setting selects display resolution for all measurement functions.
The DIGITS setting has no effect on the remote reading format. The number of displayed digits does
not affect accuracy or speed. Those parameters are controlled by the SPEED setting (see
(on
Setting display resolution
To set display resolution, press the
DIGITS
key until the desired number of digits is displayed.
Available display resolutions: 4.5, 5.5, and 6.5 digits.
Remote digits programming
The following table summarizes digits commands. See
(on page 5-1) for more
information.
Digits commands
Commands Description
display.smua.digits = display.DIGITS_4_5
Set display to 4.5 digits.
display.smua.digits = display.DIGITS_5_5
Set display to 5.5 digits.
display.smua.digits = display.DIGITS_6_5
Set display to 6.5 digits.
Digits programming example
-- Select 5.5 digits.
display.smua.digits = display.DIGITS_5_5
Speed
The
SPEED
key is used to set the integration time, or measurement aperture, of the A/D converter
(period of time the input signal is measured). The integration time affects the usable digits, the
amount of reading noise, and the reading rate of the instrument. The integration time is specified in
parameters based on the number of power line cycles (NPLC), where 1 PLC for 60 Hz is 16.67 ms
(1/60) and 1 PLC for 50 Hz is 20 ms (1/50).
In general, the fastest integration time (0.001 PLC) results in the fastest reading rate, but also causes
increased reading noise and fewer usable digits. The slowest integration time (25 PLC) provides the
best common-mode and normal-mode noise rejection, but has the slowest reading rate. Settings
between the fastest and slowest integration times are a compromise between speed and noise. The
default power-on speed setting is NORMAL (1 PLC).