why voltage output is zero?

[新学生]

Hi, I need your help

my program is to measure the volatge displaying and save the data to the file.

My questions are:

1. On the x-scale of  wave graph, time is not computer's real time, I once compared with the sample code, wave graph properties are almost the same with the sample, but it doesn't change anything. Attached pic shows.

2. no output is shown.  both from the saved data and wave graph.

What's the probelm?

Alyssa

[Dennis_Knutson]

Some of these issues were already addressed in your earlier post here. You've got the Clear Task wired up all wrong again. The concept of auto-indexing a result through a loop was also mentioned. You are only passing the last value out of the loop. You don't get a real-time display in the chart because you don't provide that information. Look at the shipping example called Real-Time Chart. You need to use a property node to set the x-axis to the current date and time when you don't use a waveform data type.

[smercurio_fc]

There also seems to be a fundamental problem of not understanding dataflow. You are closing the DAQ session while the loop is running. You also need to brush up on proper wiring such as making wires flow left to right. You have wires on top of each other, making future debugging difficult. I would suggest reading the LabVIEW tutorial sections that deal with dataflow.

[新学生]

Thank for your reply.

I still don't understand :

1.there is no clear task vi in my program, how it does the clear task?

2. I tried to remove the while loop, but "input file name" dialogue will pop up every data.

I do confused about the loop when it can  get data through directly.

[新学生]

could you please tell me where I can find the tutorial of dataflow? Thanks

[smercurio_fc]

1. See figure:


2. This tells me that you're probably trying to use the continuous run button. You should not do this. Please look at the examples as Dennis mentioned.

There's a tutorial that comes with LabVIEW. You can also head over to the NI Developer Zone Learning Center.

Message Edited by smercurio_fc on 07-24-2007 02:23 PM