Urgent, please help

[burcu]

Hello,


I am trying to acquire pressure signals from the parallel port in order to calculate flow and volume waveforms and some time data related to flow waveform.
but i have some problems;

1- i need to automaticaly measure and digitally display the inspiration time and expiration time which are related to flow waveform; inspiration time is the total duration of flow travilling on the positive side and expiration time is the duration of flow travelling on the negative side.

2- my sample rate is 200 Hz in the waveform graph. should i use and array to combine x and y values and should i use 0.005 value for x-axis.

3- when my pressure signal is zero at the input, i see 24 value on the inport at labview. how can i deal with it and pull the value to zero for zero input value.
other vaules of input are accurate. when i send 255, i see 255 on inport function.

i am attaching my code, an example flow graph, and i will send a screenshot of my block diagram at my next message.

thanks for your help.

Burcu

[rpursley8]

I got this info from the following site. Check it out and it may help.

http://www.beyondlogic.org/spp/parallel.htm#4


Bi-directional ports use Control Bit 5 connected to the 374's Output Enable so that it's output drivers can be turned off. This way you can read data present on the Parallel Port's Data Pins, without having bus conflicts and excessive current drains.

Bit 5 of the Control Port enables or disables the bi-directional function of the Parallel Port. This is only available on true bi-directional ports. When this bit is set to one, pins 2 to 9 go into high impedance state. Once in this state you can enter data on these lines and retrieve it from the Data Port (base address). Any data which is written to the data port will be stored but will not be available at the data pins. To turn off bi-directional mode, set bit 5 of the Control Port to '0'.

However not all ports behave in the same way. Other ports may require setting bit 6 of the Control Port to enable Bi-directional mode and setting of Bit 5 to dis-enable Bi-directional mode, Different manufacturers implement their bi-directional ports in different ways. If you wish to use your Bi-directional port to input data, test it with a logic probe or multimeter first to make sure it is in bi-directional mode.

[burcu]

Thanks,
How can I automaticaly measure and digitally display the inspiration time and expiration time which are related to flow waveform; inspiration time is the total duration of flow travilling on the positive side and expiration time is the duration of flow travelling on the negative side.

[JenK]

To measure the time of "inspiration and expiration" use the Elapsed Time VI located in Functions>>All Functions>>Time & Dialog. To display the time just create a numeric indicator. You will need to know in your program at what point you switch from inspiration to expiration so you can display the time accurately.

[chryboxv]

Hi,

My problem's related to t he above, I have a DAQ constantly measuring volume and pressure for inhalation and exhalation, however I don't know how to make the program automatically switch between inhalation and exhalation when it happens.

The graph show above is what happens when I am driving the system, but I have no way of knowing exactly when the switchover will happen. I thought LabVIEW may be able to detect it for me and make the adjustments accordingly, however the system I use doesn't always produce perfect loops (they are sometimes jagged because of noise) so if i used a simple mathematics comparison, it may or may not be enough, depending on how it worked.

Has anyone got any suggestions?

chryboxv