SECTION 8. PROCESSING AND PROGRAM CONTROL EXAMPLES

Input Location Labels:

8.3 USING CONTROL PORTS AND

1:Rain (mm)

 

LOOP TO RUN AM416

 

MULTIPLEXER

2:15min tot

 

 

This example uses an AM416 to measure 16

*

1

Table 1 Programs

copper-constantan thermocouples and 16

01:

60

Sec. Execution Interval

Model 223 soil moisture blocks. The sensors

01:

P3

Pulse

are read every ten minutes and the average

value output once an hour. The multiplexer is

01:

1

Rep

housed in an AM-ENCT enclosure to minimize

02:

1

Pulse Input Chan

thermocouple errors created by thermal

03:

2

Switch Closure

gradients. A 107 Temperature Probe is

04:

1

Loc [:Rain (mm)]

centrally located on the multiplexer board and

05:

.254

Mult

used as a thermocouple temperature reference.

06:

0

Offset

 

02:

P92

If time is

The AM416 switches the 223 moisture block

out of the circuit when it is not being measured.

01:

0

minutes into a

This eliminates the need for the blocking

02:

15

minute interval

capacitors used in the model 227 soil moisture

03:

10

Set high Flag 0 (output)

block. The 223 blocks are about one fifth the

03:

P80

Set Active Storage Area

cost of the 227 blocks.

 

01:

3

Input Storage Area

Control ports are used to reset the AM416 and

02:

2

Array ID or location

clock it through its channels. The sequence of

04:

P72

Totalize

the program is:

• Measure the 107 probe located at the

01:

1

Rep

02:

1

Loc Rain (mm)

AM416 for TC temperature reference.

 

 

 

• CR10 sets the port high which resets the

05:

P89

If X<=>F

AM416.

01:

2

X Loc 15min tot

• A loop is entered; within each pass:

02:

2

<>

• The port clocking the AM416 is pulsed.

03:

0

F

• The connected TCs and moisture blocks

04:

30

Then Do

are measured.

06:

P80

Set Active Storage Area

• CR10 sets the port controlling AM416 reset

low.

01:

1

Final Storage Area 1

• Soil moisture measurements are converted

02:

25

Array ID or location

to block resistances.

07:

P77

Real Time

The input location in which the temperature and

01:

110

Day,Hour-Minute

soil moisture measurements are stored is

08:

P70

Sample

indexed to the loop counter (Instruction 87,

Section 12). An indexed location is

01:

1

Reps

incremented by one with each pass through the

02:

2

Loc 15min tot

loop. For example, on the first pass

09:

P95

End

temperature is stored in Location 2, and soil

moisture in Location 18. On the second pass

10:

P

End Table 1

temperature is stored in Location 3, and soil

moisture in Location 19. After 16 loop passes,

temperature and soil moisture measurements occupy Locations 2 through 17 and 18 through 33, respectively.

Connections are shown in Figure 8.3-1.

8-3