Campbell CR9000, Instruction Manual

Page: 136 / 218

Section 7. Measurement Instructions
7-22
PulseCount (Dest, Reps, PSlot, PChan, PConfig, POption, Mult, Offset)
This instruction should not be placed in a conditional or in a Slow Sequence
Scan. Sets up pulse measurements using the twelve 16 bit counter channels
on the CR9070 or the twelve 32 bit counters channels on the CR9071E
Counter module. There are three pulse types or configurations that may be
measured using these Counter modules:
High Frequency: All twelve pulse channels can be configured for high
frequency inputs. This configuration is used for the higher
frequency pulse inputs (up to 1 MHz). The pulse count is
incremented when the signal rises from below 1.5 VDC to
above 3.5 VDC. Because of the input filter's 200
nanosecond time constant, higher frequencies will require
larger input transitions. See section 3.4 for additional
measurement information. The minimum pulse width that
can be detected is 500 ns. The maximum input voltage is
±
20 V.
Low Level AC: The first 8 frequency input channels can be configured for
low level ac inputs. This option is used to count the
frequency of low level ac signals from such sensors as a
magnetic pick up. The minimum input voltage that can be
counted is 25 mV RMS. At this minimum voltage,
frequencies up to 10 kHz can be measured. For input
voltage greater than 50 mV, frequencies up to 20 kHz can
be measured. Again, the maximum input voltage is 20 V.
Switch Closure Channels 9 through 12 can be configured as Switch
Closure inputs. The switch closure (dry contact) should be
connected between the pulse channel and ground. When
the contact is open, the pulse channel is pulled to 5 volts
through a 100 kOhm pull up resistor. When the contact is
closed, the pulse channel is pulled to ground. The count is
incremented when the channel is pulled high. The
minimum switch close time is 5 msec. The minimum
switch open time is 5 msec. The maximum bounce time
without being counted is 1 msec open.
Using the Poption, you can configure the output as Counts, Frequency over
the scan interval, or as a running average frequency for a set duration. See
section 3.4 for more pulse measurement details.
Parameter
& Data Type
Enter
PULSECOUNT INSTRUCTION
Dest
Variable or
Array
The Variable in which to store the results of the instruction. When Reps are used the results are stored in
an array with the variable name. An array must be dimensioned to have elements for all the Reps.
Reps
Constant
The number of repetitions for the measurement or instruction.
PSlot
Constant
The number of the slot that holds the 9070/9071E Counter Timer Module for the measurement.
PChan
Constant
The number of the pulse channel for the measurement.