data logging over a serial port

[mudithadias]

Hi,

I've been reading about labVIEW instrument control and I'm a bit confused. I am wondering if it possible to accquire data (voltage) from an instrument to display/store in a computer through labVIEW without the use of a DAQ device. I mean just by communicating through a serial port either by direct connection or by using a bluetooth serial adapter?

Thank you

[Dennis_Knutson]

DAQ devices have nothing to do with instruments. You would normally connect with GPIB, Ethernet, USB, or serial. All depends on what your instrument supports and what speed you want to communicate. Serial is the slowest.

[mudithadias]

Thank you Dennis. So are DAQ devices used to just enable faster communication?

[Dennis_Knutson]

DAQ devices are used for a variety of uses. Acquiring multiple voltage, current, digital, counter channels with a single device.

[mudithadias]

Thank you for the reply.

I'm trying to read voltage signals over a com port (with a serial to USB adapter). I haven't had much experience with labVIEW and although

I have been reading through posts I still havent found anything that gives me a clear introduction. Really appreciate if anyone could direct me to a tutorial or an example.

Thanks again.

[Dennis_Knutson]

Like http://www.ni.com/webcast/3189/en/ 

What sort of instrument? Saying you have a converter is meaningless. There are several thousand instrument drivers that you can look to for examples. You have a34401 DMM driver included with LabVIEW. If you have an instrument with a driver, chances are it comes with an example.

[mudithadias]

Sorry for being vague.

It's not exactly an instrument. It's a photomultiplier tube connected to a circuit board which can be connected to the computer through a serial to USB adapter. It spits out the signal as photon counts (number of counts). Currently we have a labVIEW program (developed by another person) that accquire the data and display/save it. But the program has a lot of complicated additional features and it has been giving trouble. So, im trying to develop a VI just to read and save the data from the photomultiplier tube.

Thanks!!

[mkossmann]

Well, without knowing more about the photomultiplier device its difficult to say much.  Only : Its probably possible.

Is there any "low level" documentation how to access that device ? I.e. information about serial settings to use, protocols, commands and dataformats used by that device ?  Without reading that it will be difficult to start from scratch.

Do you have access to the sources of the existing program ? Looking into these sources will also give you an idea how to access the device. However, because that program is giving trouble, there is probably still a bug in that program.

[mudithadias]

Hi, the photomultiplier is a Hamamatsu HC135. We have the serial port settings (9600,0,8,1) Im not sure what you mean by dataformats..the user manual gives commands in ASCII and hexadecimal. There are commands to change the voltage and integration times.

I don't if the following is helpful or not but the manual says:

"Once the command is issued to take a reading, the host must be ready to receive data as it is sent. The HC135 does not buffer the readings. Once the readings are collected, the data usually needs conversion to printable ASCII decimal digits. That is, each byte sent by the HC135 is a portion of a 32 bit value in binary format"

Does this mean we can log the data out of the port straight on to labVIEW program?

Thanks for the replies!!

[Dennis_Knutson]

Yes, it sounds like that should work.