PID Controller in SignalExpress?

[belliott]

Hi all,

I'm on the point of ordering some equipment from NI and in addition to datalogging I need to write a controller for an external device (PID, whatever) - for clarity - I want to read a voltage from a sensor and output another voltage to the actuator to set the sensor output to whatever value I need.  Nothing fancy.

So can I do this in SignalExpress?  Or do I need the full version of LabVIEW?

It seemed to me from the online documentation that it's possible to route an input signal through various filters and onto an output channel.  If this is true then I guess I only need to know if the componets I need to build a controller (add/subtract,integrate,differentiate,etc) are available in signalexpress(?)  If they're missing, is it straightforward to import them from the full version/download them from somewhere/something else?

Many thanks in advance

Ben

[JesusG · Accepted solution]

Hi Ben,

Signal Express is a configurable application software to do data acquisition and logging, NOT control applications. But, if your application consists of adquiring and outputting voltages or another kind of physical phenomena through signal conditioning, it is your software. For instance, you can acquire voltage, current, temperature, strain, ....

You can download Signal Express with a 30 day evaluation licence:

http://joule.ni.com/nidu/cds/view/p/id/1378/lang/es

During these 30 days the software will keep the whole funcionality. You can also read the tutorial I send you in this post.

On the other hand, you cannot modify Signal Express environment importing new functionalities, but you can use hardware filters if they are supported by the hardware module and software filters in Add Step tab >> Processing >> Analog Signals >> Filter. You can also do extra processing with the options of that tab. Have a glance into it!!

If you are spanish, you can contact us directly on 91 640 00 85.

Saludos!!!

Jesus

[belliott]

Thanks Jesus,

I'd basically come to the conclusion that I need the full labview - but your reply confirms it!  It's a shame I have to pay the extra (I'm trying to stretch the research budget as far as I can!) as I'll hardly touch all the advanced stuff in Labview, but I guess there's no other way.

I'll be sure to call if I have problems,

Hasta luego,

Ben

[DFGray]

I must disagree with my colleague on this one.  SignalExpress can be used in control applications, with a few caveats.

1. Loops are generally software timed, so subject to the vagaries of Windows for jitter.  If your loop time is long enough (slow heater control, for example), this would not be an issue.  In addition, it is possible to time the loops using triggering from your hardware, in which case your timing will be much tighter.
2. SignalExpress has standard math functions but does not contain integration or derivative capabilities directly.  So a straight proportional loop is fairly easy.  Integration can be done on a point by point basis by simply summing your inputs.  Derivatives can be taken similarly, but require at least two points, so are not as simple.
3. SignalExpress can be expanded through the use of the User Step.  However, writing a User Step requires a full version of LabVIEW, so this will not help you much.

In summary, it may be possible to do what you want to do with SignalExpress.  It may be easier in LabVIEW (depending on your programming expertise).  We would be happy to look at this further if you could give us a few more details, such as loop rates, data acquisition hardware, etc. that you need.

Note that if SignalExpress does not meet your needs, please post an idea for improving it here.  Thanks!