The required limit for Equipment Grounding Conductor is < 1 Ohm.
The meter use for the verification was calibrated from 500 ohms - 40 Megaohm as per their cal report… For Digital Resistance meter was calibrated from range 1.0 X 10E3 - 1.0 X 10E10. The calibration house do specify that their capability is to calibrate till 1.0 X 10E10 only. The required limit of ESD Control items per table 2,3 & 4 is more than 1.0 X 10E4 and less than 1.0 X 10E11 ohm.
I did issue a finding on this with reference measuring equipment must be capable of measuring of 1 decade above and 1 decade below of the required limit of ESD Control items. The client does not agree on the finding and asking - Any industrial standard the calibration require to be perform on intended value ?
ANSI/ESD S20.20 does not require test equipment to be calibrated. The paragraph in section 7.4 that states “The test equipment selected shall be capable of making the measurements defined in the compliance verification plan.” has a note immediately after that says “NOTE: Calibration certificates do not ensure test equipment is capable of making the required compliance verification measurements.” The best way to ensure the test equipment is capable of making the required compliance verification measurements is to check the manufacturer’s specifications. Although I agree it is a best practice to ensure the test equipment is calibrated in the ranges required, I agree with the client that this should not be a finding. I do think it should be a recommended area for improvement.
A couple of notes on the limits you mentioned. For the Equipment Grounding Conductor there is no requirement to do compliance verification. This is a one-time initial verification. It is also not required if the facility has a GFCI installed per footnote 5. If the meter you mentioned is the meter used for initial verification, I agree they should consider measuring it again with a meter calibrated to < 1 ohm.
Tables 2, 3, and 4 all have the highest maximum resistance limit of 10^9 ohms except for the Static Control Garment which does have a limit of 10^11 ohms. If the client does not use Static Control Garments, then the calibrated range you stated would be good as it does go an order of magnitude above the 10^9 ohm limit for all other ESD control items. If the client uses Static Control Garments in their ESD program, then I they should consider having the resistance measurement apparatus calibrated to 10^12 ohms
Hi Andy, Thanks for reply.
If same meter is used for verifying the wrist strap connection (non monitored) which have a required limit of < 2 ohm. Is my finding still valid?
Yes. This would be the same issue although I wouldn’t call it a finding but an opportunity for improvement since ANSI/S20.20 does not require calibration