Chief Delphi - 2015 Ventura Regional

Dave / Eric,

I was original inspector who made this call - based my (EE professional 44yrs)
and others inspectors past experience with RS-775, camera, & sensor chassis almost dead shorts showing up as thousands to hundreds of thousands ohms "falsely" but revealing a "smoking gun" at chassis to Anderson connector terminals.

Problem using the 10K rule at Anderson tp Pass Robot:
(symptom 1000's to multi 100K ohms measured at Anderson)

robot problems developed when root cause was ~0.1 - 0.3 ohm at motor terminal to case, (or sensor, pot, switch, camera)

Due to electrical isolation through multi-semiconductor junctions which are weakly forward biased by DMM current source compliance voltage (yielding high ohms), MASKing downstream low resistance <1ohm short to the chassis

.. with implications making large robot chassis a radio frequency radiator (antenna) of high frequency components of fast PWM rising and falling edges,

possibly interfering with this &/or other robot control or communications systems.

My interpretation is that any non diminishing resistance reading is indicative of a low resistance short somewhere on the robot.

Early-on I informed team captain and mentor Eric they may request LRI review to override my chassis isolation call.

I acted in best interest of their and all competing teams by searching out root cause determination, utilizing my personal previous hands-on robot and team experience using my professional Electrical Engineering formal education and 44 years industry microelectronics design, implementation, and troubleshooting experience.

Note after Eric removed all ckt bkrs a reading of less than 6K ohms was observed, justifying continued concern to identify root cause.

Later Eric said problem was traced to the teams DMM ohmmeter function being defective, which I rejected. As chassis ~300k ohm reading was "steady" i.e. non impulse, non-diminishing, not a transient chassis capacitive ohmmeter current source compliance voltage charge-up, which would be ignored.

No defect in the meter was indicated.
I had the team captain do DMM acceptance test:
probes: 1. open=read "OL" 2. shorted ~1 ohm, verifying proper ohmmeter function

Had the ohmmeter given ANY reading other than over range with probes "open" on the 2000K scale (2M ohm max) the meter would have been rejected.

I prefer teams use their own meters for the experience training and understanding gained.

It is NEVER my intent to make teams spin their wheels, in fact quite the opposite; I streamline wherever possible. I've been in their shoes with my team! I deeply sympathize -been there done that, had that pressure!

I always act in their and competing teams BEST interests.

It is all too easy, even incompetent to let such potential problems... slide.

(if RI has insufficient area expertise, team is always encouraged to bring in LRI "especially" if long troubleshoot time develops, second opinion is welcome, appropriate (as in this case, immediately after the first ohmmeter reading, I suggested team solicit LRI review of my "call")

By teams action it appeared at the time they were in agreement with my call

Robot rules are written carefully as possible but cannot cover every nuance.

Imperative should be "Do the right thing" !! Inspector education, experience, rules interpretation & judgement in specific situations, especially with past precedence, as in this case, should prevail, and applied with compassion for all.

When is it OK to waive such indication (let problem exist)
in order to save "time"? or appease stressed out team on inspection day?

Chassis short to motor terminal =large body interference PWM edge radiator:
Interference potential in this case to radio, processing &/or communication systems, such root cause action IMHO is well justified.

Dale K3MNN, EE w/44 years prof electronics industry, 18+ yrs FIRST