!Convert the FET switchbox base address to decimal and store the value in a
!variable.
COM Base_addr
Base_addr=DVAL("1FDC00",16)
!Set up the (external) voltmeter for DC voltage measurements, external
!triggering, and store the readings in voltmeter memory until all measurements
!have been taken.
OUTPUT 722;"PRESET NORM"
OUTPUT 722;" MEM FIFO"
OUTPUT 722;" NPLC 1"
OUTPUT 722;" TRIG EXT"
OUTPUT 722;" EXTOUT RCOMP,NEG"
!Call the subprogram which downloads the scan list, sets the settling time, and
!triggers the scan. The unstrained references are measured on this scan.
CALL Fet_scan
!Pause the program until stress is applied to the specimen. Call the subprogram
!again to set up the scan for the strain measurements.
PAUSE
CALL Fet_scan
!Enter the unstrained references and strain measurements from the multimeter
!into the computer. Call the subprogram to compute the strain.
ENTER 722;Vout_unstr(*),Vs_unstr,Vout_str(*),Vs_str
CALL Strn_cmput(Vr(*),Vout_str(*),Vout_unstr(*),Vs_str,Vs_unstr)
END
!Subprogram which sets up the scan list.
SUB Fet_scan
COM Base_addr
!Clear old the scan list and set up the Scan Control Register for the next scan.
OUTPUT 70900;"DIAG:POKE";Ba6;",16,#H1"
OUTPUT 70900;"DIAG:POKE";Ba6;",16,#H0"
!Download the scan list. Scan bridge output channels 0, 1, 2; and bridge
!excitation channel 15.
OUTPUT 70900;"DIAG:POKE";Ba10;",16,#H6000"
OUTPUT 70900;"DIAG:POKE";Ba10;",16,#H6001"
OUTPUT 70900;"DIAG:POKE";Ba10;",16,#H6002"
OUTPUT 70900;"DIAG:POKE";Ba10;",16,#H600F"
!Set the settling time from when the channel advance pulse is received,
!until the channel closed pulse is generated (32.768 msec).
OUTPUT 70900;"DIAG:POKE";Ba8;",16,#HF"
!Set the switchbox to be externally triggered.
OUTPUT 70900;"DIAG:POKE";Ba6;",16,#H02"
!Initiate the scan by closing the first channel in the list.
OUTPUT 70900;"DIAG:POKE";Ba4;",16,#H10"
SUBEND
!Subprogram which computes the measured strain.
SUB Strn_cmput(Vr(*),Vout_str(*),Vout_unstr(*),Vs_str,Vs_unstr)
FOR I=1 TO 3
Vr(I)=Vout_str(I)/Vs_str-Vout_unstr(I)/Vs_unstr
Epsilon(I)=-4*Vr(I)/2.11E-6*(1+2*Vr(I))
PRINT Epsilon(I)
NEXT I
SUBEND
136 Strain Gage Register-Based Programming
Appendix D
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