Transponder Tags on Carbon Fibre

(This is in the somewhat RF-hostile environment of our downstairs hallway, with assorted nearby metal objects and electrickery that wouldn't be around at the trackside, so take the longer range values with a pinch of salt.)

Re-configured MultiReader to do an inventory run using the trackside aerial at full power.  This reads all tags within range many times per second, with an indication of how long since each one was last successfully read.  It therefore becomes immediately clear when a tag is failing to read reliably.  We want a reliable read for race timing, as the more reads Impinj gets, the more accurately it can determine exactly when the tag crossed the finish line.

I will send my race number plate as a control test. Known to work at distances over 10 meters (even when behind the antenna) but under 20 meters. Also a replacement wheel access cover made of ABS. And finally a carbon fiber sheet with an ABS transponder mounting plate on it.

Thanks for your help with this.

All the best.

Roy

The tag without conductive material was now readable at 14.5m: performance was, unsurprisingly, better than indoors.  This is consistent with the "Range 14m" sticker that Andrew has at some point attached to the aerial, and the way the system regularly picks up tags on people milling around from the opposite side of the track.  (The race timing software can show us which aerial the read comes from, and it's usually the one on the far side, rather than the nearer one picking them up behind its back.)

The tag mounted directly to carbon fibre was unreadable, even touching the aerial.

On CF with various shims:

We also repeated a few measurements on aluminium:

The difference in performance between materials with a 5mm shim is interesting.

So yeah, you might want a bit more than 5mm on carbon fibre, but should be safe with 10mm or so.

ABS replacement cover 18 grams

Original carbon fiber access panel 14 grams.

Thanks for the new tags Kim.

All the best.

Roy