RavensFan and Billko,
I tried using Hyperterminal from Hilgraeve because I use Win 7 OS and no communications whatsoever. My settings are matching everywhere (Device Manager, MAX and LabView). So now, i'm thinking maybe the RS232 to USB cable I am using (not supplied with instrument, just got it from ebay) might be the problem. The equipment is too old to get support from the manufacturer. So, is is possible to wire a custom RS232 cable and sort this out? Also, I will be procuring two brand new scales from Mettler in maybe 10 days which come with cables as a part of the package.
But I wanted to have a working program for my purpose in time for the new scales so was testing with the older models. Any suggestions?
Ugh, USB? That opens up an additional can o' worms...
The PC I have has no serial ports. Sorry I thought serial to USB wouldn't cause problems (very sorry).
 - More details - Intrument to RS232 coupler to RS232 cable to USB to USB port on PC.
If I switch out PC's to one that has a RS232 port, would that be better?
No worries - you expect something like a USB to Serial port to work if the driver doesn't throw errors. It's just that some USB adapters seem to be more "compatible" with LabVIEW than others. 🙂
But, I have another PC sitting around doing nothing with two RS232 ports (an old PC). If it's better I can easily do that, just have to talk to NI and get them to give me a trial version on that one too.
Wherever you got your software from (download or DVD) should function as a trial if you don't enter serial numbers, so you should be able to install it on your old PC. Make sure the trial is exactly that, though - a trial.
You don't even need to install LV on the old computer at this point. Just use Hyperterminal and send an idn? or some simple command to see if it it talking correctly. If it is, then your issue may be your USB to Serial adapter. I didn't see any mention of drivers from the adapter. Did you install them prior to use?
If not you can plug anything you what into the serial port and you wont data any data into your LV program. One way to check your driver is to see if Windows is recognizing it. Go to Start, right click Computer, Manage, Find and click Device Manger in the new window, expand Ports. It should say something like USB to serial adapter... and show you the corresponding COM port in was assigned. If not, load your adapter driver.
If you can see it in Device Manager, then you are back to a communications issue with your device. Make sure you use the COM port listed next to your serial adapter. My suggestion is to keep it simple and get a response from your scale first to verify your communication settings and cabling.
The port is set up properly on Device manager. The first time I plugged the USB to the port , I asked windows to find the drivers and it did. So I was under the impresion it is setup properly. So i'm thinking either the cable is bad or device not sending anything but I have tested it under every setting (Handshake, Printer setting and SBI setting). And i'm really not sure what to do now.
- If it is a cabling issue, how do I sort it out. For example, if the internal wires are all wrong for the device, how do I find that out?
Here's the screenshot of the Data interface manual for the device describing Pin assignment. I am going to have to read up on cables to figure out what null and straight is.
 - Its a straight through cable. just figured it out.