CRIO and electromagnetic interference

Hi, we’re looking to place our CRIO 1 inch from our CIMS, and wondering if this willl be a problem with 30 amps next to it.

While I don’t have empirical data I have to believe that National Instruments has built the CRIO to be robust in hostile industrial environments which include much larger and noisier motors and other sources of EMI.

I would be shocked if the CIM were able to cause any problems for the C-rio. They could cause some slight trouble for something like a gyro, but it’s not like it’s a huge noisy motor.

If you’re really worried about noise you can add a 1 uF non polarized capacitor across the motor leads (the closer to the motor the better).

Will at 1uF capacitor do anything significant for a CIM?
Would this require splicing the leads of the motor near its base?

Honestly I’d be more worried about noise from inductive backlash (inductors get so cranky when you cut them off!)

The cRio is pretty hardened, it should be fine, ours is sandwiched between the Jags on either side with the CIMs on the third side and the primary power routed along the fourth. Ours is in a storm of EM power and it hasn’t batted an LED at it.


According to the spec sheet:

This product is designed to meet the requirements of the following standards of EMC for electrical equipment for measurement, control, and laboratory use:

  • EN 61326 EMC requirements; Industrial Immunity
  • EN 55011 Emissions; Group 1, Class A
  • CE, C-Tick, ICES, and FCC Part 15 Emissions; Class A

So yes, it does meet some sort of standards for electromagnetic interference resistance.

I found a PDF listing some requirements for EN 61326, although the paper uses technical terms beyond my understanding.

I wouldn’t worry about it too much, as we’ve placed ours pretty close to 2 CIMs last year and didn’t have a problem.

Capacitors on the motors are good insurance. You may need to experiment with the value of the capacitor that you put on any particular motor. A smaller capacitor, say 0.01 uF, will kill high frequency noise better than a larger capacitor, say 1 uF.

Our team has experienced interference from the CIM’s causing the D-Link to drop it’s connection each time the motor started up. At a different location (probably with less electrical noise flying around) it works fine.

There are different EMC Immunity standards, each with different levels. The only think they have in common is that your equipment will not be damaged by the EMC directed at it. At the higher levels, the equipment must continue to operate correctly in the pressence of the EMC. At the lower levels, it is permissible for the equipment to malfunction in the pressence of the EMC and will resume proper operation once the EMC is removed. At the lowest level, the equipment is allowed to reset when the EMC is applied.

<R63> A signal filter may be wired across motor leads or PWM leads. For the purposes of inspection and rules compliance, such filters will not be considered custom circuits, and will not be considered a violation of Rule <R47> or Rule <R62>. Acceptable signal filters are:
 **A one microfarad (1 μF) or less non-polarized capacitor **may be applied across the power leads of any motor on your ROBOT (as close to the actual motor leads as reasonably possible)

However, I have never used this method and never needed it.