ESD floor resistance tests use weighted electrodes to make electrical contact with the flooring. Several methods specify nominal five-pound electrodes, but their dimensional tolerances differ. An electrode should therefore be checked against the requirements of the test method being used, rather than selected by weight alone.
Craftsman Concrete measures floor resistance for flooring systems installed by Craftsman and other contractors. Reviewing electrode specifications, condition and preparation helps the facility’s ESD program team determine whether the measurement setup is appropriate and whether equipment checks or further testing may be needed.
ANSI/ESD STM7.1-2020, ANSI/ESD STM97.1-2025, ESD TR53-01-22 and ASTM F150-25 specify electrode dimensions, conductive-contact properties and a resistance check on a metallic surface. The requirements below distinguish those specifications from cleaning procedures and electrode-condition concerns.
Electrode specifications by method
Weight and diameter
The four documents specify cylindrical electrodes with a nominal weight of 2.27 kg (5 lb) and a nominal diameter of 63.5 mm (2.5 in). Their permitted tolerances differ.
| Method | Mass | Diameter |
|---|---|---|
| ANSI/ESD STM7.1-2020, section 5.2 | 2.27 kg ± 0.06 kg | 63.5 mm ± 5% |
| ANSI/ESD STM97.1-2025, section 5.3 | 2.27 kg ± 0.06 kg | 63.5 mm ± 3 mm |
| ESD TR53-01-22, section 6.14 | 2.27 kg ± 2.5% | 63.5 mm ± 5% |
| ASTM F150-25, section 5.2 | 5 lb ± 1 oz (2.27 kg ± 28 g) | 2.5 in ± 0.062 in (63.5 mm ± 1.58 mm) |
Conductive-contact hardness
All four specify electrically conductive contact material with a Shore-A durometer hardness between 50 and 70 under ASTM D2240. Durometer hardness describes the material’s resistance to indentation.
ASTM F150-25 specifies two metal electrodes and describes their contact hardness as Shore-A (IRHD) 50 to 70 under Test Method D2240.
Checking and preparing the electrodes
Resistance between the two electrodes
Each document requires resistance between two electrodes to be below 1.0 × 10³ Ω when measured on a metallic surface. ASTM F150-25 expresses the limit as 1 kΩ and specifies measurement at 10 volts or less.
This checks the electrode pair on metal. It is not a floor resistance acceptance limit.
Cleaning before STM7.1 installed-floor testing
The ANSI/ESD STM7.1-2020 installed-floor acceptance procedure directs cleaning the resistance measurement electrode with an isopropanol-water solution and a clean, low-linting cloth, then allowing it to air dry before testing (section 6.2.1.1).
A 70% isopropanol-water solution is given as an example.
Electrode checks during TR53 troubleshooting
The footwear/flooring troubleshooting sequence in ESD TR53-01-22 includes two electrode checks (section 7.2.3.3):
- Examine the electrodes for contamination buildup. Remove surface contamination according to the manufacturer’s recommendations and allow adequate drying time before retesting.
- Using the resistance measurement apparatus and appropriate leads, verify that the electrodes can measure resistance values above and below the expected measurement range.
These checks address contamination and measurement capability before the floor’s performance is judged from the readings.
Can electrode condition or contact type change the result?
Warped conductive rubber contacts
Conductive rubber electrode contacts can warp over time and change measurements. ANSI/ESD STM97.1-2025 identifies no standardized method for checking whether this warping has occurred (section 5.3 note).
Electrode condition therefore remains relevant when investigating differences between resistance readings.
Hard and resilient contacts in the historical study
A 1959 National Bureau of Standards study found that hard electrodes made less contact and produced higher resistance readings than resilient electrodes on the hard-surfaced flooring samples tested.
Those findings illustrate why electrode contact matters. They do not establish a universal correction factor for other floors or justify substituting a different electrode for the one required by the applicable test method.
Frequently Asked Questions
Yes. Craftsman Concrete reviews the electrode specifications, condition and preparation as part of floor resistance testing for systems installed by Craftsman or other contractors. The review helps the facility’s ESD program team determine whether equipment checks or further testing may be needed.
No. ANSI/ESD STM7.1-2020, ANSI/ESD STM97.1-2025, ESD TR53-01-22 and ASTM F150-25 specify similar nominal weights and diameters, but their tolerances differ. Each also specifies electrically conductive contacts with Shore-A hardness from 50 to 70 under ASTM D2240. Weight alone does not establish that an electrode meets a particular method’s requirements.
The resistance between the two electrodes must be below 1.0 × 10³ Ω, or 1 kΩ, under the cited provisions of all four documents. ASTM F150-25 additionally specifies measuring at 10 volts or less. This is an electrode check, not the acceptance limit for the flooring.
Yes. ANSI/ESD STM97.1-2025 recognizes that conductive rubber contacts can warp over time and change measurements. It identifies no standardized method for verifying whether this has occurred (section 5.3 note).