User Manual

2400 Series SourceMeter
®
User’s Manual Range, Digits, Speed, and Filters 7-7
Speed
The Speed/Accuracy menu is used to set the integration time 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 ultimate 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 60Hz is 16.67msec (1/60) and 1
PLC for 50Hz and 400Hz is 20msec (1/50).
In general, the fastest integration time (FAST; 0.01 PLC) results in increased read-
ing noise and fewer usable digits. The slowest integration time (HI ACCURACY;
10 PLC) provides the best noise rejection. In-between settings are a compromise
between speed and noise. The default power-on speed setting is NORMAL (1
PLC).
NOTE For the Pulse Mode of the Model 2430, the valid NPLC range is 0.01 to
0.1 PLC.
The speed setting affects both the NMRR (normal mode rejection ratio)
and CMRR (common mode rejection ratio). Normal mode noise is the
noise signal between the HI and LO input terminals, while common mode
noise is the noise signal between LO and chassis ground. See
Appendix A for NMRR and CMRR specifications.
Setting speed
Speed is set from the Speed Accuracy menu and is structured as follows. Use
Section 1, “Rules to navigate menus,” to check and/or change the speed setting.
NOTE For the Pulse Mode of the Model 2430, speed is set from Pulse Speed
menu. This menu structure is located after the Speed Accuracy menu.
Use the “
Rules to navigate menus” in Section 1 to check and/or change
the speed setting.
Front panel speed control
Press SPEED or CONFIG SPEED to display the menu.
• FAST — Sets speed to 0.01 PLC and sets display resolution to 3H digits.
• MED — Sets speed to 0.10 PLC and sets display resolution to 4H digits.
• NORMAL — Sets speed to 1.00 PLC and sets display resolution to 5H digits.
• HI ACCURACY — Sets speed to 10.00 PLC and sets display resolution to
6H digits.
• OTHER — Use to set speed to any PLC value from 0.01 to 10. Display res-
olution is not changed when speed is set with this option.