ESD Resistance Limit Values - Which Numbers Apply?
Resistance values decide whether an ESD workstation dissipates charge to standard. This guide sorts the upper and lower limit values under IEC/DIN EN 61340-5-1 for people, floors, mats and packaging and shows how to read measured results correctly.
View ESD test equipmentWhat do upper and lower limits mean?
ESD control almost always works with a window between an upper and a lower limit. The upper limit makes sure charge drains fast enough; the lower limit keeps the discharge current safe if a person touches live voltage. Together they define the safe operating band.
Resistance is read on a logarithmic scale in powers of ten: the step from 10⁶ to 10⁹ Ω is a factor of 1000. That is why materials are grouped as dissipative (10⁵ to 10¹¹ Ω), conductive (below 10⁴ Ω) and insulative (above 10¹¹ Ω).
- Conductive: below 10⁴ Ω - drains very fast, the lower bound for personnel grounding.
- Dissipative: 10⁵ to 10¹¹ Ω - the classic ESD working range.
- Insulative: above 10¹¹ Ω - holds charge, unwanted inside the EPA.
- Test voltage: usually 10 V for lower ranges, 100 V for higher ranges.
Which limits apply to each element?
IEC 61340‑5‑1 sets its own limits for every element of the EPA (ESD Protected Area). The table below summarises the common requirements - the current edition of the standard for your site is always the binding reference.
How do you measure and interpret readings?
Measurements use a resistance meter with defined electrodes (2.5 kg load, 100 V for high ranges). Stable climate conditions are critical, because humidity and temperature shift the values noticeably - dry winter air pushes resistance upward.
A value just below the upper limit is no reason to worry as long as it stays reproducible. Problems appear with strongly fluctuating readings, when a floor or surface exceeds 10⁹ Ω, or when a wrist strap drops below 7.5 x 10⁵ Ω - because then the protective series resistance is missing.
- Log the climate: record relative humidity and temperature at the time of measurement.
- Measure several points per surface, not just the centre.
- Clean surfaces with an ESD cleaner before measuring.
- Document any limit breach and find the cause (wear, silicone film, loose ground).
- Set test intervals: wrist strap daily, surfaces and floors periodically.
Frequently asked questions
What is the key upper limit under IEC 61340-5-1?
For floors, working surfaces and the person-footwear-floor system, the resistance to ground is generally required to be below 1 x 10⁹ Ω (1 GΩ). Above that, charge drains too slowly.
Why is there also a lower limit?
The lower limit caps the discharge current. For a wrist strap it sits at 7.5 x 10⁵ Ω, so that the protective series resistance remains effective if the person contacts live voltage.
Does humidity affect the readings?
Yes, significantly. Low humidity raises the measured resistance. That is why climate values are always logged and tests are repeated under critical conditions.
What is the difference between Rg and Rp?
Rg is the resistance to ground; Rp is the point-to-point resistance across a surface. Both are tested because they represent different discharge paths.
Measuring resistance to standard?
We supply resistance meters, electrodes and complete ESD test kits - matched to the limit values of IEC 61340-5-1.
Standard-based
All limit values per IEC 61340-5-1.
Measurable
Meters with defined electrodes and test voltage.
Documentable
Log values and keep intervals reliably.
Expert advice
ESD specialists help with selection and test plans.