# Convert sheet resistance and thickness to Sigma correctly

Sigma is bulk conductivity in inverse ohms per model length unit. Convert thickness to the LDF length unit before using sheet resistance.

## Compatibility

8 beta/preview

Published guidance with release-applicability limits. Confirm package applicability before following this guide.

## Use consistent units

For a uniform thin film, Sigma = 1 / (sheet resistance × thickness). Express thickness in the model's length unit. With micrometre units, the result is in ohm^-1 micrometre^-1.

A generic example: sheet resistance 2 ohm/square and thickness 0.1 micrometre give Sigma = 5 ohm^-1 micrometre^-1. These are illustrative values, not a recommended fabrication process.

## Check the active material model

A per-layer value can override the global Sigma. The manual also states that defining Lambda for a layer makes Sigma and MuR inactive for that layer. Confirm the intended normal-conductor or superconducting model before interpreting a conductivity change.

## Verify

Inspect the effective process definition and use a simple resistive example to check units and geometry. A plausible Sigma does not prove that the contacts and current path are correct.

## Sources and verification details

Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.



- support:SUP-010: Generalised editorial finding; outcome qualification retained
- inductex:docs/manual/ix_ldf.tex: Global and per-layer Sigma; Units; Lambda

- Support history informed this draft. Current-source guidance has been checked; a fresh walkthrough on the intended distributed release and product-owner review remain pending.

## Related guides

- [Adding a process layer breaks a connection or shorts a port](/knowledge-base/inductex-process-connectivity)