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SECTION 9. INPUT/OUTPUT INSTRUCTIONS

9-17

*** 26 TIMER ***

FUNCTION

This instruction will reset a timer or store the

elapsed time registered by the timer in seconds in

an Input Storage location. Instruction 26 can be

used with Program Control Instructions to measure

the elapsed time between specific input conditions.

There is only one timer and it is common to all

tables (e.g., if the timer is reset in Table 1 and later

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 0.1* second

increments. The maximum interval that can be

timed is 46.6 days.

The timer is also reset in response to certain

keyboard entries:

1. When tables are changed and compiled

with the

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 AVERAGE (SE) ***

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 1.1 milliseconds

transpires while counting those cycles (e.g., if

the maximum input frequency is 10 kHz, choose

at least 11 cycles to be measured). If the time

for the number of cycles is less than 1.1

milliseconds, an overrange value (displayed as -

99999) will be stored for the measurement. The

specified number of cycles are timed with a

resolution of 12 nanoseconds, making the

resolution on the period 12 nanoseconds

divided by the number of cycles measured.

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 9-8. Period Average Output Options/Range Codes

Range

Code

Voltage

Gain

Minimum

Signal (pk-pk)

Maximum

Signal (pk-pk)

Minimum

Pulse Width

Maximum

Frequency

x4 1.0 500 mV 10.0 V

2.5 µs

200 kHz

x3 5.0 40 mV 2.0 V

10 µs

50 kHz

x2 20 5 mV 2.0 V

62 µs

8 kHz

x1 100 2 mV 2.0 V

100 µs

5 kHz

x = 0 Output Period in µs x = 1 Output frequency in Hz

1 - Signals must be centered around datalogger ground to trigger zero-crossing detector.

2 - Maximum frequency equals 1/(Twice Minimum Pulse Width) for 50% duty cycle signals.

1 2 ... 146 147 148 149 150 151 152 153 154 155 156 ... 373 374

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Campbell CR23X Spécifications Page 151

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