Electrical reference chart
Insulation Resistance Test Chart
Use this worksheet after the calculator result to record equipment ID, test voltage, temperature, readings, polarization index, corrected value, baseline, and action note.
Quick reference table
An insulation resistance test chart is a calculator-led testing worksheet. It keeps megger readings, temperature correction, PI, baseline comparison, and follow-up notes together before acceptance or maintenance decisions.
Insulation resistance test worksheet
| Item | Record from calculator | Follow-up |
|---|---|---|
| Equipment | ID, class, voltage rating | Confirm isolation and discharge procedure |
| Test setup | Test voltage, temperature, duration | Record instrument and leads |
| Readings | One-minute, ten-minute, corrected value | Compare with baseline |
| PI or trend | Calculated ratio or status | Review with equipment history |
| Action | Retest, dry-out, investigate, or accept note | Route to qualified reviewer |
Insulation trend review lanes
| Review lane | Record on worksheet | Why it changes the action |
|---|---|---|
| Test setup | Megohmmeter model, test voltage, lead arrangement | Different setups can change readings |
| Temperature correction | Winding or equipment temperature and factor | Trend values need a comparable basis |
| Polarization behavior | 1-minute, 10-minute, PI, absorption note | A single reading can miss moisture or contamination trends |
| History comparison | Baseline, last test, maintenance action | The trend often matters more than one value |
How to use this chart
Confirm isolation first
Document equipment isolation, discharge, lockout, and instrument rating before relying on readings.
Keep readings tied to conditions
Record temperature, test voltage, duration, and equipment condition with every result.
Compare against history
Use the chart to compare corrected values and PI against baselines or manufacturer guidance.
Formula basis
Polarization index = 10-minute insulation resistance / 1-minute insulation resistance.
- One-minute reading is the insulation resistance recorded after one minute of test voltage.
- Ten-minute reading is the insulation resistance recorded after ten minutes when PI is used.
- Temperature correction factor adjusts the measured value to a reference temperature when applicable.
- Baseline is a prior result from the same equipment or a documented acceptance basis.
Worked examples
Motor insulation record
Record equipment ID, test voltage, winding temperature, one-minute reading, ten-minute reading, PI, corrected value, baseline, and maintenance action.
Dry-out retest worksheet
Keep pre-dry-out reading, corrected value, temperature, dry-out duration, retest value, and manufacturer follow-up together before closing the maintenance note.
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Frequently asked questions
These answers explain how to use the chart without turning a quick reference into a final design decision.