choising an I/O module

[dhirah]

Hello,

I was wondering how can we choose an I/O module? my module needs to cover an input which varies from 0 to 25 V and with this module, we can choose a square signal, continue or triangle. Which module matches my characteristics? i've read the datasheet and i came across NI 9221. Can i use this module?

What do TTL,Sink/source mean? when the datasheet indicates that the signal level is 60VDC, does it mean it cover from 0 to 60?

Thank you.

Dhirah

[Graziano]

Hi!
   You have to provide more details: are you building a PC based system? I mean, are you looking for a PCI board to install on your PC, or are you going to build a compact RIO system (embedded)?

   The module you choose is for compact RIO, and it has only INPUT channels (not output).  It is an analog input module, in which input can vary from -60 V to + 60 V (so, it is suitable for your needs).

    Sinking/sourcing refer to output modules, from an NI manual: "Sinking current means the Vout terminal provides a path to the supply common." "[]...sourcing
outputs, which means that the output terminal provides a path to a voltage supply."

   In other ways, with sinking, the swith cuts the "common" wire, while in sourcing it is the positive voltage that is cut.

graziano

[dhirah]

Hye!

Thanks for replying!

Well, i'l building using the NI cDAQ 9172. That module that ive chosen is also compatible to NI cDAQ. actually i need a module whiwh has analog Input and output. It should support a variation from 0 to 24V. Can we choose a module which allows us to choose between continuous, triangle ans square signal?  certain modules like NI 9481 has a characteristic of logic-form A. What is that suppose to mean?

thanks again!

Dhirah

[Graziano]

Hi!
   NI 9481 is a RELAY output, it is not an ANALOG output module! You need an analog ouput module to generate arbitrary functions, that vary from 0V to 24 V continuously.

  please clearify your task! Do you need digital outputs or you really need to generate functions? Usually 24 V is used in industrial automation plants as digital...

   Anyway, for Analog out modules, look among these, in particular define sampling rate (rate at which samples are generated), DAC resolution (number of bits), etc...

graziano

[Graziano]

Hi!
   output modules there seems to be +/- 10 Volt....

graziano

[dhirah]

hi!

i verified my task and it seemed that ill be needing a relay/digital output and input. So, what do you think of NI 9474 and  NI 9422. Actually, im qquite sure about the output but the input seems a lilttle bit confused with it's characteristic. Mind giving me your opinion? Thanks!

Dhirah

[Graziano]

Hi!
   Your task seems not really clear

   If you need 24 Volt input/ output, NI 9422 and NI 9474 are good.

   NI 9422:
   Number of channels..........................8
   Input type..........................................Sinking/sourcing
   Digital logic levels
   OFF state
   Input voltage ........................≤ 5 V
   Input current.........................≤ 0.17 mA
   ON state
   Input voltage ........................ 11 to 60 V
   Input current.........................≥ 1.2 mA

   Ni 9422 is a DIGITAL input module.  I cannot find max sampling frequency achievable, I only read 250 us max delay in input.

    NI 9474 is a digital output module, with 8 channels, sourcing. i.e. when you turn on the single channel, you provide + 24 Volt to the load.  You have to carefully read the manual to check if it fulfills your load's specifications!

   If you need Relay out,NI 9481 has 4 relays (4 output channels), SPST.  I've found no more relay modules, this is a problem if you need more sofisticated relays  (SPDT, etc....), you'll have to turn to another system, or you integrate some other electronics.

graziano

PS.: this was the my last answer for free to have better details you can phone NI, they're really kind both in commercial and support!




Message Edited by Graziano on 04-17-2008 09:15 AM