Campbell CR3000 Micrologger, Руководство оператора

Страница: 412 / 644

Section 8. Operation
412
Measurements include time between edges expressed as frequency (Hz) or period
(µs).
C Terminals
•
Maximum input frequency <1 kHz
•
CRBasic instruction: TimerIO()
•
Rising or falling edges of a square-wave signal are detected:
o
Rising edge — transition from <1.5 Vdc to >3.5 Vdc.
o
Falling edge — transition from >3.5 Vdc to <1.5 Vdc.
•
Edge-timing resolution is approximately 136 ns.
8.1.3.6 Edge Counting
Edge counts can be measured on C terminals.
C Terminals
•
Maximum input frequency 400 kHz
•
CRBasic instruction: TimerIO()
•
Rising or falling edges of a square-wave signal are detected:
o Rising edge — transition from <1.5 Vdc to >3.5 Vdc.
o
Falling edge — transition from >3.5 Vdc to <1.5 Vdc.
8.1.3.7 Timer Input on I/O NAN Conditions
•
NAN is the result of a TimerIO() measurement if one of the following
occurs:
o
Timeout expires
o
The signal frequency is too fast (> 3 KHz). When a C terminal
experiences a too fast frequency, the CR3000 operating system
disables the interrupt that is capturing the precise time until the next
scan is serviced. This is done so that the CR3000 processor does
not get occupied by excessive interrupts. A small RC filter
retrofitted to the sensor switch should fix the problem.
8.1.3.8 Pulse Measurement Tips
Basic connection of pulse-output sensors is illustrated in table Switch Closures
and Open Collectors
(p. 413,
p. 413).