Temperature & Pressure control in a vessel

[jas1991]

Hello,

I would like to implement a LabVIEW software for the following situation:

We will be mixing methane and water in a vessel. This vessel will be heated up to 92 C in order to meet the pressure requirements (1 atm). The temperature will be risen by a heating tape which can supply up to 288 W (120VAC). So we are measuring by a thermocouple and a pressure transducer the conditions at the inlet.

We are thinking to acquire the product NI 9211, since it can accurately read the temperature from the thermocouple, and since the transducer is connected directly to the computer we do not need to have it connected through a NI card. So what we want to do in LabVIEW is control the heating tape voltage according to the temperature and pressure demands in the vessel.

So, I am only asking for hardware advice, since I think it can be easily integrated in LabVIEW as there are many examples for such case, just that I am wondering we are using the apropiate hardware for that process.

Regards

Joan

[moderator1983]

Acquisition of Pressure (directly to the computer) and Thermocouple (through NI 9211) is done...!!

What about controlling the heating tape..!! How are you planning..??

Is it goanna be ON-OFF controller or a PWM based or PID...??

If you select either ON-OFF or PWM, you need a digital output or a counter output (in case of PWM)... Otherwise if you go for PID you might need an analog output signal....!! And for any of these you need an additional DAQ card with either digital, counter or analog voltage output capability.

[jas1991]

Yes, I understand the Temperature and Pressure connection.

The heating tape is thought to be ON-OFF controlled, for instance after reaching 92 C and 1 atm, we no longer don't need to supply any more heat.

I am just wondering if with the NI 9211 it is possible to connect a relay output in which we can drive the heating tape from there.

That is my main concern

Thanks

[moderator1983]

No, Check specifications tab.

NI 9211 has no channel other than 4 Analog Input.

By other channels I mean:

-> Analog Output

-> Digital Input/Output

-> Counter Channel

[jas1991]

Yes, and since we haven't got the NI 9211 because we cannot drive our heating tape I want to know if there's another hardware which can do both our demands, or at least have a relay output it which we can connect our heating tape as well as a thermocouple to control both.

[johnsold]

Get a module with a digital output and use that to control a solid state relay (SSR).  The NI 9481 relay module will not quite handle the power of your heat tape.

Lynn

[jas1991]

I heard that is possible to connect a heating element to a NI USB 60009, however I know that its accuracy might not be sufficient for our temperature measurements. So, as you are suggesting the module, which one from NI would be most suitable for our case?

I am guessing from your comments that I might have to purchase a temperature input module and a relay control module separetely. So we might get the NI9211 for the thermocouple readings and still missing about the heat tape module connection, which besides connecting it to a SSR I do not know how to integrate that with the computer and as well with LabVIEW

[AndyClegg]

Joan - first decide if you are happy with control running in PC with appropriate IO modules, or if you want control to run on true real-time target (like cRIO) with PC simply acting as interface to controller (permanent or temporary). Either way you can use the c-series IO modules (like NI 9211, or NI 9219), but they need to go in different chassis. For digital relay outputs you'll need to look at the current drive requirements you have, and see if either solid state relay (NI 9485) or electromechanical relay (NI 9481) can supply what you need. Might be easiest just to use low power Digital Output channel and have that drive an external relay. Advantage of separating them is that if relay fails it is cheap/easy to replace.

Hope this helps,

[jas1991]

Thank you all for your different types of solutions.

Since we have the NI USB 6009 and thus the temperature measurement we are going to obtain for the thermocouple is not going to be as accurate as we want, we are looking for an integrated unit which has both a thermocouple/thermisor with an amplifier in order to directly obtain that better resolution and thus to ease our work when connecting and setting it up with LabVIEW

Thanks