Displaying STate of an Analog Output on Test kit (0-10v and 0-20mA)

[Buflonob]

Looking at chucking a trainign/testing kit together for some of our kits.

Having the idea of using a small display to represent the analog value that we choose to output through one of the controllers analog outputs.

Problem is, we are unaware of the technology available to diplay these values when the outputs are changed from the aforementioned modes or output, and if possible, recognise the change and switch accordingly.

Does anyone know of anything that may be suitable?

 

[Skogsgurra]

No. I do not know about any such instrument. But it could be done - no problem really.

You can use the fact that a 4-20 mA circuit always has a compliance voltage that is at least 24 V and that the minimum current in a functioning circuit is 4 mA.

Now, if you connect a high impedance instrument, it will show compliance voltage. The high voltage (more than 10 V) will switch the instrument to current mode (switching in a load resistor and subtracting 4 mA). It has to latch in that state or you will see it switch to and from current mode indefinitely.

If this instrument is connected to a 0-10 V signal, it will stay in voltage mode. Load resistor and offset not active.

That's how I would do it. But there are probably other ways as well.



Gunnar Englund

http://www.gke.org

 

[ewbdale]

Buflonob,

Red Lion manufacture some programmable displays. I would talk with them explain what you are trying to accomplish
they may have a unit that does that.

http://www.redlion.net/

or

http://www.redlion.net/Products/DigitalandAnalog.html

Let me know if this site helps.


Ernie

http://rasp-controls.com/