Communication problems with a Serial connection to a Pressure Gauge

[DrRob2020]

Hello folks, I am trying to establish communication with a VACOM MVC-3 Vacuum gauge. The manual for the gauge can be found at: 

https://www.vacom.de/en/downloads/category/775-total-pressure-measurement?download=2440:mvc-3

I am having problems understanding how to communicate with the device. I am using the built in COMM port (Port 1) of my computer (Windows 10 Enterprise, 64 bit, version  10.0.18363 build 18363) and I have configured the device to have a baud rate of 9600 and to use RS232  as described on page 45 of the manual.

I am trying to communicate with the device in NI Max as I get the feeling from these pages that this is the best way to start..

In Visa I set the Baud rate =9600

data bits = 8

stop bit=1

parity=none

flow control= none

I enabled a termination character.

End mode for reads=TermChar

End mode for writes = Termchar

Termination character= carrage Return \r

Now I started trying to communicate with the simplest command possible , RVN<CR>. (to read the version number P 52 of the manual)  and I always get a read error Visa: Hex 0xBFFF0015 Timeout...

In the manual I noticed that they want you to enter the commands in ascii. Does that mean I should convert RVN<CR> to 82 86 78 0x0D or something like that?

Should I write the command and just read, or is there some kind of acknowledgement command that needs to be sent first. (I get vibes from this from page 49 but I am not sure) 

Also, since Visa is configured to use \r format as the termination character, does this pose a problem for communicating with this kind of device?

Thank you in advance people.

Happy Weekend

DrRob2020

[crossrulz]

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@DrRob2020 wrote:

Now I started trying to communicate with the simplest command possible , RVN<CR>. (to read the version number P 52 of the manual)  and I always get a read error Visa: Hex 0xBFFF0015 Timeout...

...

Also, since Visa is configured to use \r format as the termination character, does this pose a problem for communicating with this kind of device?

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You should be sending "RVN" followed by a Carriage Return.  You can configure VISA to send it for you (Send End Enable and Send End Mode I think are the properties you need, I don't use them).

[DrRob2020]

Hello crossrulz 

Thank you for your quick response. I had attempted this before but it is not working. Am I doing something stupid? Also are there restrictions on how long serial connections can be before signals degrade? I am currently using 10 m (2*5m connected by gender changers) of shielded serial cable:

https://se.rs-online.com/web/p/serial-cable-assemblies/1116151/?relevancy

Thanks again

DrRob2020

[Albert.Geven]

Hi

Are you sure that your connection is correct, Are the send and receive connections correct or swapped? If not check both connectors or use another cable.

Straight and swapped are available for serial, swapped is sometimes named a Null modem cable.

[crossrulz]

So quickly going through the manual, I see a few things to watch out for.

1. Make sure the internal jumper for the controller is set up for RS-232.  There is an option to set it to RS-485.

2. Make sure you are using the same baud rate as the controller.  It could be 9600, 19200, or 38400 with the default being 19200.

3. The fact that you used a gender changer scares me.  You should not have to do that.  If you do, you likely have a NULL Modem cable on one side, which would cause your RX and TX lines to be swapped and you will not talk.  Buy a cable that meets your length requirement, is a straight through cable, and has a male on one side and a female on the other side.