Campbell Scientific SDM-INT8 8-Channel Interval Timer - Manual (Page 28)

SDM-INT8 8 Channel Interval Timer
Parameter 6 (Capture All Events) is programmed for 20--to capture edge times
on channels 1-5 until 20 edges are received on channel 1.
Flag 2 is used in the example to indicate the start of the cranking. In actual test
program, this flag could be set in response to an ignition switch measurement
indicating the start of the test.
When the ignition is turned on (Flag 2 set), Instruction 101 is called, and the
INT8 is programmed. A "loop with delay" is entered to delay for 10 seconds.
The Output Flag is set high before executing Instruction 101 again to retrieve
the test data.
Three arrays with the following Output array IDs are transferred to the
datalogger's Final Storage.:
105 - Stored are hour:minute, seconds, channel 1 frequencies (kHz).
106 - Stored are crank angle results (teeth on flywheel).
107 - Stored are fuel injector pulse widths (ms).
Array 105 - Each time the crankshaft reference is reached, a pulse is generated
on channel 1. INT8 measurements are started by the initial (trigger) pulse on
channel 1. The pulse frequency (kHz) will be stored on each subsequent pulse
on channel 1 (one pulse per revolution). The pulse frequency can be converted
to RPM by multiplying by 60,000. This conversion must be done in the
computer, after the test.
Array 106 - Channel 2 receives one pulse each time a flywheel tooth passes a
fixed reference point. When a crank shaft reference pulse occurs (channel 1),
the crankshaft is in a known position. Each time a spark plug fires, a pulse
occurs on channel 3. The output for channel 3 is the number of pulses that
have occurred on channel 2 since a pulse from the crank shaft reference
(channel 1). A value (number of pulses) will be output for each cylinder in
their respective firing order. Every fourth data value in Array 106 will
correspond to the same cylinder. The crank angle at each firing can be
calculated by multiplying the number of teeth since the crankshaft reference
pulse by 360/N, where N is the total number of teeth on the flywheel and
subtracting this quantity from 360.
Array 107 - Channel 4 senses a rising edge when the fuel injector is activated.
Channel 5 senses a falling edge when the fuel injector is deactivated. The
INT8 calculates the time (ms) between these two edges, thereby calculating the
pulse width, or the length of time the fuel injector is on for each pulse.
*Table 1 Programs
01: .5 Sec. Execution interval
1: If Flag (P91) If ignition is
1: 22 2 is reset (Ignition not on) on, execute
02: 0 Go to end of Program Table following
2: Do (P86) address/prgm INT8
1: 1 Call Subroutine 1
22