Operator`s manual

SECTION 3. INSTRUCTION SET BASICS
3-2
counter. The loop counter is added to the
indexed value to determine the actual input
location the instruction acts on. Normally the
loop counter is incremented by 1 after each
pass through the loop. Instruction 90, Step
Loop Index, allows the increment step to be
changed. See Instructions 87 and 90, Section
12, for more details.
To index an input location (4 digit integer) key C
after keying the value but before entering the
parameter. Two minus signs (-) will be
displayed to the right of the parameter.
3.5 VOLTAGE RANGE AND
OVERRANGE DETECTION
The RANGE code parameter on Input/Output
Instructions is used to specify the full scale
voltage range of the measurement and the
integration period for the measurement (Table
3.5-1).
Select the smallest full scale range that is
greater than or equal to the full scale output of
the sensor being measured. Using the smallest
possible range will result in the best resolution
for the measurement.
Two different integration sequences are
possible. The slow integration, 16.67
milliseconds, is one 60 Hz cycle and rejects
noise from 60 Hz AC line power as well as
having better rejection of random noise than the
fast integration. A PROM with 50Hz rejection is
available for countries whose electric utilities
operate at 50Hz (Appendix B).
When a voltage input exceeds the range
programmed, the value stored is the maximum
negative number, displayed in the *6 Mode as
-99999. In output data from Final Storage this
becomes -6999 in low resolution or -99999. in
high resolution.
An input voltage greater than +8 volts on one of
the analog inputs will result in errors and
possible overranging on the other analog inputs.
Voltages greater than 16 volts may permanently
damage the 21X.
TABLE 3.5-1. Input Voltage Ranges and Codes
Range Code Full Scale Range Resolution*
Slow Fast
16.67ms 250µs
Integ. Integ.
111±5 millivolts 0.33 microvolts
212±15 millivolts 1. microvolts
313±50 millivolts 3.33 microvolts
414±500 millivolts 33.3 microvolts
515±5000 millivolts 333. microvolts
*Differential measurement, resolution for single-ended measurement is twice value shown.
3.6 OUTPUT PROCESSING
Most Output Processing Instructions require
both an intermediate processing operation and a
final processing operation. For example, when
the Average Instruction, 71, is executed, the
intermediate processing operation increments a
sample count and adds each new Input Storage
value to a cumulative total residing in
Intermediate Storage. When the Output Flag is
set, the final processing operation divides the
total by the number of sample counts, stores the
resulting average in Final Storage and zeros the
value in Intermediate Storage so that the
process starts over with the next execution.
Final Storage is the default destination of data
output by Output Processing Instructions
(Sections OV1.2, 1.5, 2.1). Instruction 80 may
be used to direct output to Input Storage or to
Final Storage.
Output Processing Instructions requiring
intermediate processing sample the specified
input location(s) each time the Output Instruction
is executed, NOT necessarily each time the