NI 9220 Maximum Altitude

[bjcancin]

Hello

I need to use 3xNI-9220 at a altitude of 2700m. The NI-9220 module with DSUB output is specified for altitudes less than 2000m, so in theory it should use the SPRING output. The issue is that the connection through DSUB is much more robust than the SPRING, because you do not have to connect each terminal separately.

Investigating a bit in the forum, the problems with altitude are mainly due to the fall of the dielectric constant of the air. My question is this: The maximum altitude specification for the NI-9220 is due only to the high voltage protections? or is it also due to the possibility that internal electronic faults exist if the specified altitude is exceeded ?.

I hope you can help me.

Regards!

[SaileshK]

bjcancin,

As far as I know, the altitude specification of 2000m exists mainly for high voltage protections (you are correct in stating that the change in dielectric constant of air in creating a higher chance of arcing).

[Larry_Morgan]

Hello,

Both versions of the 9220 are only rated for 2000m operation. I think you're probably referencing one of my other responses where I point out the dielectric strength of air decreases with altitude, causing us to put a maximum operation altitude. 

You have noticed the isolation ratings are different for the spring and dsub. This is necessary in many products because of the necessary creepages and clearances of the connectors to guarantee product safety. Unfortunately DSUB does not meet the criteria to allow 250Vrms CATII safety isolation. 

But there is another safety rating that isn't as apparent. If you notice in the "Hazardous Locations" section, you will see ratings like the following:

Class I, Division 2, Groups A, B, C, D, T4;

Class I, Zone 2, AEx nA IIC T4

The "AEx nA" part of that rating is called "non-sparking", which is just about what it sounds like. It won't spark, arc, or have exceedingly hot surfaces. There are also gas/dust groups encoded in there as well as surface temps. I point all that out to summarize that these hazardous location ratings are sometimes even more stringent than the safety isolation ratings and can end up as the main reason for setting the altitude rating. It may not necessarily just be the connector.

Unfortunately we cannot guarantee or warrant any operation outside of the listed specifications, but hopefully this gives you some insight into where they came from.

 Best of luck!

[bjcancin]

Hi. Thanks for the reply.

As a clarification, according to the latest version of the datasheet (http://www.ni.com/pdf/manuals/378023a_02.pdf), pag. 10, the maximum altitude for the Spring connector is 4000 m.

We have already purchased three of the modules with a Spring connection and we are going to re-evaluate the option to change them for the DSUB terminal.

Thanks!

[Larry_Morgan · Accepted solution]

Right you are about the new rating! I was looking at an older revision.