National Instruments Welding System 321645c-01 Manual De Usuario

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Chapter 2
Function Reference — GPCTR_Set_Application
NI-DAQ FRM for PC Compatibles
2-238
©
 National Instruments Corporation
6602 and 455X devices with counter width 32 bits, you can generate pulses with a delay and 
length between 100 ns and 214 s long.
Figure 2-25.  Buffered Period Measurement
Typically, you will find modifying the following parameters through the 
GPCTR_Change_Parameter
 function useful when the counter application is 
ND_BUFFERED_PERIOD_MSR
. You can change the following:
ND_SOURCE
 to 
ND_INTERNAL_100_KHZ
. With this timebase, you can measure intervals 
between 20 µs and 160 s long. The resolution will be lower than if you are using 
ND_INTERNAL_20_MHZ
 timebase. 
ND_SOURCE_POLARITY
 to 
ND_HIGH_TO_LOW
 
ND_GATE
 to any legal value listed in the 
GPCTR_Change_Parameter
 function 
description
ND_GATE_POLARITY
 to 
ND_NEGATIVE
. Measurements will be performed between 
successive high-to-low transitions of the signal present at the gate.
To provide your timebase, you can connect your timebase source to one of the PFI pins on the 
I/O connector and change 
ND_SOURCE
 and 
ND_SOURCE_POLARITY
 to the appropriate values. 
You also can configure the other general-purpose counter for 
ND_PULSE_TRAIN_GNR
, and set 
ND_SOURCE
 of this counter to 
ND_OTHER_GPCTR_TC
 to measure intervals longer than 160 s. 
Note
The counter will start counting as soon as you arm it. Be aware of this when you 
interpret the first count in your buffer.
Caution
If gate edges arrive and no source edges are present between those gate edges, then 
the previously saved value is saved again as shown in Figure 2-25. Please make 
sure that this condition does not occur during your measurement.
Source
Gate
Buffer
2
1
4
3
6
5
1
7
3
2
5
4
1
6
3
2
4
Measured
Period
Measured
Period
Measured
Period
7
7
6
7
6
 4
!