Campbell CR7 Manuel d'instructions télécharger pdf (Page 44)

SECTION 3. INSTRUCTION SET BASICS

3-2

Even though this display is the same as that

indicating an indexed input location, (Section

3.4) there is no indexing effect on excitation

voltage.

3.4 INDEXING INPUT LOCATIONS

When used within a Loop, the parameters for

input locations can be Indexed to the loop

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 one 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 50 Hz (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 CR7.

TABLE 3.5-1. Input Voltage Ranges and Codes

Range Code Full Scale Range Resolution*

Slow Fast

16.67ms 250µs

Integ. Integ.

1 11 ±1500 microvolts 50 nanovolts

2 12 ±5000 microvolts 166 nanovolts

3 13 ±15 millivolts 500 nanovolts

4 14 ±50 millivolts 1.66 microvolts

5 15 ±150 millivolts 5 microvolts

6 16 ±500 millivolts 16.6 microvolts

7 17 ±1500 millivolts 50 microvolts

8 18 ±5000 millivolts 166 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

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 185 186

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