National Instruments 320571-01 用户手册

Performs a discrete differentiation of the
sampled signal X.  The differentiation f(t) of a
function F(t) is defined as follows:

f(t)  =  

d

dt

  F(t).

Let Y represent the sampled output sequence
d/dt X.  The discrete implementation is given
by the following formula:

y

i

  =  

1

2dt

  (x

i+1

 - x

i-1

)                     for i = 0, 1, 2, …, n-1.

where n is the number of samples in x(t)

x

-1

 is specified by initial condition when i = 0, and

x

n

 is specified by final condition when i = n-1.

initial condition and final condition minimize the error at the boundaries.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input
signal array.

initial condition defaults to 0.0.

final condition defaults to 0.0.

dt is the sampling interval and must be greater than zero.  If dt is less than or equal to zero, the VI
returns an error.  dt defaults to 1.0.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the
results of the differentiation of X.

Y out is a DSP Handle Cluster that is identical to Y in, but with the results of differentiation already
stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI.  If an error occurs, it is passed out
error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster.