Operator`s manual

SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-3
anywhere between one second too short to
almost twice as long. Pulses are not lost during
resynchronization so totalized values are correct
but pulse rate information such as wind speed
can be almost twice the correct value. The
discard counts from excessive intervals option
mentioned in the previous paragraph does not
correct this problem in 21Xs with PROMs
391B/392D and earlier.
The options of discarding counts from long
intervals, pulse input type, outputting frequency,
and using a sixteen bit counter are selected by
the code entered for the fourth parameter
(Table 9-2).
NOTE: All pulse count instructions
must be kept in the same table. If the
pulse count instruction is contained
within a subroutine, that subroutine
must be called from Table 2.
TABLE 9-2. Pulse Count Configuration
Codes
Code Configuration
0 High frequency pulse
1 Low level AC
2 Switch closure
3 High frequency pulse, sixteen bit
counter
4 Low level AC, sixteen bit counter
1X Long interval data discarded,
where X is configuration code
2X Long interval data discarded,
frequency (Hz) output
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions
02: 2 Channel number for first
measurement
03: 2 Configuration code (from
above table)
04: 4 Input location for first
measurement
05: FP Multiplier
06: FP Offset
Input locations altered: 1 per measurement
*** 4 EXCITE, DELAY, AND MEASURE ***
FUNCTION
This instruction is used to apply an excitation
voltage, delay a specified time, and then make a
single-ended voltage measurement. A 1 before
the excitation channel number (1X) causes the
channel to be incremented with each repetition.
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions
02: 2 Range code
03: 2 Input channel number for
first measurement
04: 2 Excitation channel
number
05: 4 Delay in hundredths of a
second
06: 4 Excitation voltage
(millivolts)
07: 4 Input location number for
first measurement
08: FP Multiplier
09: FP Offset
Input locations altered: 1 per measurement
*** 5 AC HALF BRIDGE ***
FUNCTION
This instruction is used to apply an excitation
voltage to a half bridge (Figure 13.5-1), make a
single-ended voltage measurement of the bridge
output, reverse the excitation voltage, then
repeat the measurement. The result of
Instruction 5 is the ratio of the measurement to
the excitation voltage. A 1 before the excitation
channel number (1X) causes the channel to be
incremented with each repetition.
The excitation "on time" for each polarity is
exactly the same to insure that ionic sensors do
not polarize with repetitive measurements. The
range should be selected to be a fast
measurement (range 11-15), limiting the
excitation on time to 800 microseconds at each
polarity. A slow integration time should not be
used with ionic sensors because of polarization
error.