Campbell-scientific AM16/32A Multiplexer Manual de usuario descargar pdf (Pagina 25)

AM16/32A Relay Analog Multiplexer

GENERALIZED CRBASIC PROGRAMMING SEQUENCE:

ACTIVATE MULTIPLEXER/RESET INDEX

Portset (1 ,1) 'Set C1 high to Enable Multiplexer

I=0

BEGIN MEASUREMENT LOOP

SubScan(0,sec,16)

CLOCK PULSE AND DELAY

Portset (2,1 ) ‘Set port 2 high

Delay (0,20,mSec)

Portset (2,0) ‘Set port 2 low

INCREMENT INDEX AND MEASURE

I=I+1

'User specified measurement instruction

‘Storing results in Variable(I)

END MEASUREMENT LOOP

NextSubScan

DEACTIVATE MULTIPLEXER

Portset (1 ,0) 'Set C1 Low to disable Multiplexer

In addition to precision voltage excitation, the CR5000 and CR3000

have programmable current excitation. Current excitation allows a

resistance measurement on a four-wire sensor (e.g., a PRT) such as

shown in Figure 14 using only a single differential channel and no

fixed resistor; the excitation return goes directly to ground. With the

current excitation the resistance of the relays and lead wire do not

affect the measurement.

5.3.1 CR5000 and CR3000 Programming

Although the following example is a CR5000 program, a similar

program can be used for the CR3000. This CR5000 program uses the

AM16/32A to measure 16 100 ohm Platinum Resistance

Thermometers connected in the 4x16 configuration. The program

also measures 6 copper constantan thermocouples.

CR5000 AM16/32A PRT(4 Wires)

Control/Common Sensor Terminals

C1 Reset Odd H Excitation

C2 Clock Odd L Excitation Return

IX1 COM Odd H Even H Sense wire excitation side

IXR COM Odd L Even L Sense wire return side

7H COM Even H

7L COM Even L

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Campbell-scientific AM16/32A Multiplexer Manual de usuario Pagina 25