Current loop measurement and DAQ board

[sbaudry]

Hi.
I want to acquire some values coming from sensors outputting a 4-20 mA signal.

I designed a solution with SCXI-1125 and E series card.
In other side, somebody -from NI- gave me a price offer with just E-Series DAQ card and a connecting board with resistors (and thus measuring Voltage). I can understand this solution (when the range are compatible).
So, can you explain me what are the benefits if I choose the most expensive solution (SCXI + E-series)compare to the cheapest one (E-series + resistor)

Thanks a lot.

SB.

[LucaP.]

Hi Sbaudry,

There are a lot of advantages and disadvantages. It depends always on what is important for you and in which environment you're working. If you need "only" to measure an 4-20mA signal, then I think that the E-Series+resisitor option is the cheapest and easiest way.

Advantages/Disadvantages:
- SCXI-1125 has 8 channels. If you need more. then you've to buy another one. The ESB (E-Series board) can acquire 16 channels in NRSE or RSE mode.
- The SCXI-Module has programmable low pass filters (4 and 10kHz), the ESB not.
- The SCXI-1125 has channel-channel isolation, the ESB not.
- The SCXI-1125 can measure thermocouples too and has internal CJC, the ESB not directly.
- The SCXI-1125 extens the nominal range of the ESB to +- 1000V.
- ... Check the
User Manual for more features

So the questions is: Do you need all the extra features which the SCXI-1125 is offering? If no, then I recommend you to use the resistor approach.

Regards,
Luca