Taking a look at the imp-002 specification it looks like it only needs a 250mA Power Supply while the imp-001 Card needs 400mA. Is this difference correct?
Yes. The card spec is to ensure that future cards that may be physically compatible with the socket have enough power available for whatever they might do (ie a future card rev with a different radio may require more power).
The module, being soldered down, isn’t going to change and hence the spec reflects the actual power consumption of the current module.
I assume then this implies existing -001 cards also only require 250ma max? Also, if a future card were to become available that required higher current, would this replace existing -001 devices, or would the lower current -001’s continue to be available?
Correct about imp001. A higher current card wouldn’t necessarily be a replacement for the imp001. Future wifi cards would generally have lower, not higher, power requirements.
Thanks for confirming the imp001 power Hugo … had been a question on my mind too, just never got around to asking. (Understood about the typical migration to lower power devices … was only responding to your initial comment about the possibility of future higher power radios. But I like lower power … always a good thing 
)
Actually this confirms my readings… I had the imp001 under meter for a while now and I’ve actually never got a drain higher than 180mA. I was thinking it maybe due to the environment, as the WiFi router is just a couple of meters away and it’s a very powerful one. Will start to monitor the imp002 today
Yeah, if you fall back to 11b rates, the current (and TX power) is higher. You’re likely on 11n.
@Hugo, it’s absolutely on 11n and the royter is a 2x2 MIMO 300M with 3 antennas, located nearby in the lab, that’s why I’m pretty sure that the low current used during WiFi activity (average 80mA) is related to the environment.
Do you think mimo improves the link to a device (imp) with single antenna?
Absolutely. Generally, the AP has a higher TX power & higher gain antenna, so the imp is likely to hear it just fine, so the biggest advantage here is the AP being able to hear the imp better - which MIMO helps a lot with.