Campbell CR800 Series, Operator'S Manual

Page: 378 / 598

Section 8. Operation
378
and flow meters, are calibrated in terms of frequency ( Hz
(p. 501)
) so are
usually measured using the PulseCount() frequency-output option.
•
Accuracy of PulseCount() is limited by a small scan-interval error of
±(3 ppm of scan in 10 µs), plus the measurement resolution error
of ±1 / (scan interval). The sum is essentially ±1 / (scan interval).
•
Use the LLAC4
(p. 562)
module to convert non-TTL-level signals,
including low-level ac signals, to TTL levels for input into C terminals.
• As shown in the table Switch Closures and Open Collectors
(p. 378),
C
terminals, with regard to the 6.2 V Zener diode, have an input resistance
of 100 kΩ with input voltages < 6.2 Vdc. For input voltages ≥ 6.2 Vdc, C
terminals have an input resistance of only 220 Ω.
Switch Closures and Open Collectors on P Terminals
Switch Closure on
P
Terminal Open Collector on on P Terminal
Switch Closures and Open Collectors
Switch Closure on C Terminal:
No Pull-Up