VTI Instruments EX1000A, User Manual

Page: 263 / 320

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EX10xxA Function Calls 263
vtex10xxA_set_user_conversion
F
UNCTION
P
ROTOTYPE
ViStatus vtex10xxA_set_user_conversion(ViSession vi , ViInt32 eu_conv , ViReal64 fwdcoeff[] , ViInt32 numFwd ,
ViReal64 invcoeff[] , ViInt32 numInv );
F
UNCTION
P
ARAMETERS
vi = contains a session handle to the instrument. This handle is obtained by the function and remains valid until the
session is closed.
eu_conv = the polynomial set to be defined. Value must be an integer equal to 9 (User0) or 10 (User1).
fwdcoeff[] = an array of forward conversion polynomial coefficients. Coefficients c
0
through c
12
are represented in
array elements [0] through [12], respectively.
numFwd = the length of the forward coefficients array. Valid input values: 1 through 13.
invcoeff[] = an array of inverse conversion polynomial coefficients. Coefficients d
0
through d
12
are represented in
array elements [0] through [12], respectively.
numInv = the length of the inverse coefficients array. Valid input values: 1 through 13.
D
ATA
I
TEM
R
ESET
V
ALUE
fwdcoeff[] = 0 in all array elements for both polynomial sets.
invcoeff[] = 0 in all array elements for both polynomial sets.
D
ESCRIPTION
This function sets the user-defined conversion polynomials.
The forward conversion polynomial is used to convert a CJC temperature into a compensating cold junction voltage
and has the form of:
12
12
2
2
1
1 0
* * * t c t c t c c E
     
where
E is in volts, t is in ºC, and c
o
– c
12
are the coefficients .
The inverse conversion polynomial is used to convert a compensated input voltage into temperature and has the
form of:
12
12
2
2
1
1 0
* * * E d E d E d d t
     
where
E is in volts, t is in ºC, and d
o
– d
12
are the coefficients .
Undefined coefficients are automatically set to 0.
NOTE The entry of user-defined coefficients does not automatically enable their use. The enabling is done
by setting the EU conversion to User0 or User1 through the vtex10xxA_set_channel_conversion
function.
E
XAMPLE