How To Communicate With Instrutech Vacuum Gauge Via Serial Port

[zhaolin8921]

Hello,

 

I am pretty new to DaqFactory and serial communication. 

 

My task is to read the pressure readings from the gauge per 1 second and display the reading by a text field on front page.

 

I have set up the communications between the gauge and DaqFactory. In the Comm Monitor window, I got:

 

Tx: #01RD\013

Rx: *01 9.99E+09\013

Tx: #01RD\013

Rx: *01 9.99E+09\013

Tx: #01RD\013

Rx: *01 9.99E+09\013

 

The gauge is based on ask-answer. When I send #01RD\013, it will return the reading I want. 

 

My problem now is that I can't figure out how to do it by sequence in an automatic fashion. I tried the following code:

 

private string stin
private in
while(1)
   try
 device.vacuum_gauge.Purge()
 device.vacuum_gauge.Write("#01RD\r")
 stin = device.vacuum_gauge.ReadUntil(50)
   catch()
 ? strLastError 
   endcatch
   delay(1)
endwhile

But I get an error: 

 

C1136 Timeout: read_pressure Line 7

 

 

Can anyone help me? Thank you so much!

 

Lin

 

[AzeoTech]

Two problems:

 

1) you don't want \r.  You want:

 

device.vacuum_gauge.write("#01RD" + chr(13))

 

2) you don't want to read until 50.  50 is the binary code for the ASCII character '2'.  You want:

 

device.vacuum_gauge.readUntil(13)

 

which will read until the \013 in the output, the carriage return.

 

You'll then want to parse the result.  It looks fixed field, so you'll likely just do:

 

in = strToDouble(mid(stin,3,20))

[zhaolin8921]

Thanks! It works!

 

Just one more question, if I want to display the pressure value, in = strToDouble(mid(stin,3,20)), how should I do it on the front page then?

 

Many thanks!

[AzeoTech]

I'd create a channel for it.  Call it pressure, type = "Test", A to D, Channel and D# = 0, Timing = 0.  Then add this line after the in=strtoDouble(...)

 

pressure.addValue(in)

 

Then you can just display Pressure[0] in any of the screen controls, or plot pressure vs time in a graph.

[zhaolin8921]

Thank you so much! It works just the way I want!

[zhaolin8921]

Hey,

 

I just come up with another simple question. I would like to display my result in a scientific notation (e.g. 1.23E+08) in a text box (display->variable value). But I can't find where I can change the format. Could you help me?

 

Thanks! 

[AzeoTech]

Use format():

 

format("%.3e", myVal)

 

If myVal = 1.2345e-6, then the result of the above is 1.235e-006.  Use E instead of e for 1.235E-006. The result is a string.  Format() works just like printf() a very common function.  The parameters are described in the user's guide section 4.12.9