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multimeter to an internal multiplexer. Connections are shown in Figure 4-4. This
method synchronizes the computer to the instruments and relies on the
computer to enter each reading and advance to the next channel in the scan list.
The sequence of operation is:
1. INIT (line 50) closes channel number 100.
2. The channel closure causes a pulse on Trig Out which triggers the
multimeter to take a reading.
3. When the reading is complete it is sent to the computer (lines 60 to 80).
4. The computer sends Group Execute Trigger to the multiplexer (line 90);
this advances to the next channel in the scan list.
5. Steps 2 through 4 are repeated until all channels have been scanned and
readings taken.
10 OUTPUT 722;"TRIG EXT;DCV"
Set multimeter to external trigger, DC voltage measurements
20 OUTPUT 70914;"OUTP ON" Enable Trig Out port
30 OUTPUT 70914;"TRIG:SOUR BUS"
Set multiplexer to advance scan on Group Execute Trigger or
*TRG
40 OUTPUT 70914;"SCAN (@100:115)" Specify scan list (channels 100
to 115)
50 OUTPUT 70914;"INIT" Close first channel (starts
scanning cycle)
60 FOR I= 1 TO 16 Loop through following lines
16 times
70 ENTER 722;A Enter reading (computer waits
until reading taken & received)
80 PRINT A Print reading
90 TRIGGER 70914 Trigger multiplexer; advances
to next channel
100 NEXT I
110 END
Using the Mainframe 4-5