Campbell Scientific CR510 Basic Datalogger - Manual (Page 114)

SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-10
in Table 2, a subsequent instruction in Table 1 to
read the timer will store the elapsed time since the
timer was reset in Table 2).
Elapsed time is tracked in 0.125 second
increments. The maximum interval that can be
timed is 8191.875 seconds.
The timer is also reset in response to certain
keyboard entries:
1. When tables are changed and compiled
with the
∗
0 Mode, the timer is reset
automatically.
2. Entering "
∗
6" after changing the program
compiles the programs, but does NOT reset
the timer.
PARAM. DATA
NUM. TYPE DESCRIPTION
01: 4 Input location no. of
elapsed time in
seconds (or enter 0 to
reset)
Input locations altered: 1
(0 if timer is being reset)
*** 27 PERIOD MEASUREMENT ***
FUNCTION
Instruction 27 measures the period
(microseconds) of a signal on a single ended
input channel. As an option, the frequency of the
signal in kHz may be output instead of the period.
The number of cycles to measure should be
chosen so that at least one millisecond
transpires while counting those cycles (e.g., if
the maximum input frequency is 10 kHz, count
more than 10 cycles). If the time for the number
of cycles is less than 1 millisecond, an over
range value (displayed as -99999.) will be
stored for the measurement. The specified
number of cycles are timed with a resolution of
35 nanoseconds, making the resolution on the
period 35 nanoseconds divided by the number
of cycles measured. Resolution is reduced by
noise and signals with a slow transition through
the zero voltage threshold.
The "Time out" parameter specifies the
maximum length of time the instruction will wait
on each repetition for the specified number of
cycles. If the cycles have not been counted
within this time, -99999 will be loaded into the
input location.
TABLE 9-5. Input Frequency Codes
Range Peak to Peak Volts Maximum
Code Required @ Max. Freq.* Frequency
1 2 mV 8 kHz
2 3 mV 20 kHz
3 12 mV 50 kHz
4 2 V 150 kHz**
0x Output period in microseconds
1x Output frequency in kHz
where x is range code
* AC voltage; must be centered around CR510
ground.
** Consult Campbell Scientific if higher
frequencies are required.
PARAM. DATA
NUM. TYPE DESCRIPTION
01: 2 Repetitions
02: 2 Gain/output option
03: 2 Single-ended input
channel
04: 4 # Cycles to measure
05: 4 Time out (0.01 sec, at
least the maximum
duration of the number
of cycles specified + 1
1/2 cycles.)
06: 4 Destination input
location
07: FP Multiplier
08: FP Offset
Input locations altered: 1 per repetition
*** 28 VIBRATING WIRE ***
MEASUREMENT
FUNCTION
Excites a vibrating wire sensor with a swept
frequency (from low frequency to high), then
measures the response period and calculates 1/T
2 ,
where T is the period in ms. Excitation is normally
provided before each repetition. As an option, a
single excitation can be made prior to all repetitions
of the measurement. An AVW1 or AVW4 Vibrating
Wire Interface is usually required for these sensors.