20
2.4.7
DC Sampling
The Model 2835-C incorporates two analog-to-digital, (A/D) converters, one
with 20,000 count resolution and a second with 4096 count resolution. The
user may select which A/D will be used for both channels during DC CONT
and DC SNGL acquisition modes. All other modes use the 4096 count A/D.
The 20,000 count A/D converter can operate at sample rates up to 25 Hz.
When two detector calibration modules are plugged into the meter, the 4,096
count A/D converter can operate at sample rates up to 500 Hz. When one
detector calibration module is plugged into the meter, the 4,096 count A/D
converter can operate at sample rates up to 1000 Hz.
The SAMPLE PREC menu command, Table 12, selects which analog-to-digital
converter is used for both channels. The sampling frequency for both chan-
nels can be adjusted within the limits imposed by the SAMPLE PREC state, see
Table 13. When the SAMPLE PREC state changes, the sampling frequency
defaults to 25 Hz if the existing SAMPLE FREQ is incompatible with the new
SAMPLE PREC state. The SAMPLE FREQ and the SAMPLE PREC settings affect
both channels, not just the the display channel.
Table 12 – SAMPLE PREC States and Limits.
SAMPLE PREC
A/D Accuracy
Sample Frequency Range
20000 CNT
20,000 counts
0.001 Hz to 25.0 Hz
4096 CNT
4,096 counts
0.001 Hz to 500.0 Hz or 1000.0 Hz
Table 13 – DC SAMPLING Operations.
Menu Function
Keypad Commands
Associated Remote Commands
SAMPLE PREC
Edit PREC=
20,000,
SPREC, SPREC?
4096
CNT
SAMPLE FREQ
Edit FREQ=
SFREQ, SFREQ?
ddd.ddd
HZ
2.4.8
Trigger Output
The Model 2835-C’s rear panel TTL trigger output allows it to coordinate
activities among other instruments. The trigger output can operate in several
ways: conversion complete, periodic output, comparator output and integrat-
ing comparator output. In addition, the polarity of the trigger output can be
specified.
In TRIG ON CMPLT mode, a pulse is output after each reading has been
acquired and completely processed from either channel. When acquiring on
one channel, it indicates that the 2835-C is ready to take another reading. The
width of this pulse is at least 8
µ
S.
In TRIG AT FREQ mode, a pulse is output at a user defined frequency or rate.
Each pulse width is at least 8
µ
S and the programmable frequency range of the
pulses is 0.001 Hz to 1000.0 Hz.
In TRIG ON LEVEL mode, each measurement is compared to a programmable
trigger level. The units of the trigger level always equal Watts for power
detectors or Joules for energy detectors. If a measurement is less than the
specified value, then the trigger output is inactive. If the measurement
exceeds the specified value then the trigger output becomes active. The TRIG
ON LEVEL output is a shift in level rather than a pulse.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
