apogee mq-500 working?

[JCSReefing]

I recently borrowed a apogee mq-500 par meter from my local reef club. I have 2 radion gen 3 xr-15 pros over my tank. I currently have them set to 80%blues and violet, red and green are at 5% and whites at 20%. (See pic for settings on wxm module) they are set to run at 50% intensity.
When I take a reading st the top of my rock, it's coming back around 65par. How is that possible? That's way way low with my lights at the 50% intensity.
Any thoughts??

 

[saltyfilmfolks]

A simple test would be to set them all at full and measure them at the same distance as it is listed in the factory specs.

 

[Dana Riddle]

How high are the lamps above the water level?

 

[JCSReefing]

How high are the lamps above the water level?

about 10"

 

[billw]

Did you take the cap off of the sensor?

 

[JCSReefing]

Did you take the cap off of the sensor?

Yes, there is no cover on it. this is extreamly frustraiting becasue corals seem to be doing ok but i have no idea why as soon as the sensor goes in the water it drops insanely. I don't feel like my acro i ahve in the top of my tank would still be alive if my par was truly only around 140