Specifications

Appendix A. Single-Ended Measurements
A-5
FIGURE A-2. Single-Ended Measurement
A.2 Indexing with Loops
When a multiplexer is measured with a measurement instruction within a loop, the
input locations in which to store measurements must be indexed to the loop
counter so the measurement is stored in the next input location each pass through
the loop. When more than one repetition is used on the measurement instruction,
as in examples A-1 and A-2, Instruction 90 is used to set the increment of the loop
index. With Instruction 90 correctly used, each measurement will occupy its own
input location, without being overwritten by subsequent passes through the loop.
Take the following measurement case. Six Type T thermocouples are measured
with a CR10 and AM25T. The thermocouples are wired into the AM25T as
shown in Figure A-1. Instruction 13, with two repetitions, is used to measure the
thermocouples inside a loop. With a Loop Count of three and no indexing on the
thermocouple location (Example A-3), the measurements would be stored in
Input Storage as shown in Table A-1.
Note that after the third pass through the loop, only the last two measurements
are in Input Storage. The temperatures for TC_1 through TC_4 have been
overwritten.
The multiplexer control instructions are not included in the
example program fragment.
TABLE A-1. Values in Input Storage; Input Location Not Indexed
Pass 18 19 20 21 22 23
First TC_1 TC_2
Second TC_3 TC_4
Third TC_5 TC_6
When the Input Location is indexed (see Instruction 87 in the datalogger
manual), the Loop Index counter is added to the specified input location, each
pass through the loop, to determine where the measurement is stored. By
default, the index advances by one with each pass through the loop. Simply
indexing a measurement instruction’s Input Location works, when the
NOTE