Touch voltage estimate calculator
Estimate touch voltage from entered current and path impedance assumptions for Australian protection and earthing records.
touch_voltage_V = entered_current_A x path_impedance_ohm; threshold_margin_V = entered_touch_voltage_threshold_V - touch_voltage_V; threshold_utilisation_percent = touch_voltage_V / entered_touch_voltage_threshold_V x 100; current_duration_product_A_s = entered_current_A x contact_duration_s- Current, path impedance and touch-voltage threshold are entered by the user.
- Contact duration is recorded as an exposure basis only.
- The calculator does not model human response or set work methods.
- Keep the source of each assumption with the exported record.
| Variable | Meaning | Unit | Use |
|---|---|---|---|
| I_entered | Entered current | A | Current assumption entered for the contact scenario. |
| Z_path | Path impedance | ohm | Impedance assumption entered for the touch-voltage estimate. |
| t_contact | Contact duration | s | Duration basis recorded with the worksheet row. |
| V_threshold | Entered threshold | V | Touch-voltage threshold entered by the user. |
| V_touch | Estimated touch voltage | V | Entered current multiplied by path impedance. |
| threshold_margin_V | Threshold margin | V | Entered threshold minus estimated touch voltage. |
| threshold_utilisation_percent | Threshold utilisation | % | Estimated touch voltage divided by entered threshold times 100. |
| current_duration_product_A_s | Current-duration product | A.s | Entered current multiplied by contact duration. |
More
Touch voltage estimate calculator technical guide
Estimate touch voltage from entered current and path impedance assumptions for Australian protection and earthing records.
Entered touch-voltage assumptions
Use this worksheet when a project record already has a current assumption and a path impedance assumption, and the next task is to estimate touch voltage from those entered values. The page is suitable for earthing notes, accessible-metalwork records, temporary bonding reviews and protection worksheets where the source of each assumption must stay visible.
The calculator does not decide whether a work method is suitable. It multiplies entered current by entered path impedance, compares the estimate with an entered threshold and records contact duration as a basis value beside the result.
| Input | Use in this worksheet | Must come from |
|---|---|---|
| Entered current | Multiplied by path impedance to estimate touch voltage. | Measured value, fault-current estimate, project note or competent-person record. |
| Path impedance | Converts entered current into a voltage estimate. | Project assumption, test basis, earthing note or engineering record. |
| Contact duration | Kept as a visible exposure basis. | Project procedure, test scenario or reviewer basis. |
| Entered threshold | Compared with the voltage estimate. | Project criteria, reviewer basis or authority requirement. |
Review workflow
- Identify the contact scenario and worksheet reference.
- Enter the current basis that belongs to the scenario.
- Enter the path impedance assumption used for the estimate.
- Enter the contact duration basis so it remains visible with the row.
- Enter the touch-voltage threshold source used for comparison.
- Review estimated touch voltage, threshold margin and current-duration product together.
- Keep the source of current, impedance, duration and threshold beside the exported worksheet.
If any source value changes, create a new row rather than reusing a result prepared for a different contact scenario.
Formula basis
The worksheet uses four visible relationships:
| Output | Formula | Interpretation |
|---|---|---|
| Estimated touch voltage | `entered_current_A x path_impedance_ohm` | Voltage estimate from the entered current and path impedance assumptions. |
| Threshold margin | `entered_touch_voltage_threshold_V - touch_voltage_V` | Positive means the estimate is below the entered threshold. |
| Threshold utilisation | `touch_voltage_V / entered_touch_voltage_threshold_V x 100` | Shows how much of the entered threshold is used. |
| Current-duration product | `entered_current_A x contact_duration_s` | Keeps duration visible without turning it into a human-response result. |
Worked Australian examples
A board worksheet uses 0.05 A entered current and 1000 ohm path impedance for accessible metalwork. Estimated touch voltage is 50 V, matching the entered 50 V threshold, and the current-duration product is 0.01 A.s.
A temporary bonding review uses 0.08 A and 1000 ohm. Estimated touch voltage is 80 V, so the margin against the entered 50 V threshold is -30 V and the row needs source-basis review.
A test point estimate uses 0.03 A, 1200 ohm and a 0.5 s duration basis. Estimated touch voltage is 36 V, while the current-duration product remains visible at 0.015 A.s.
Touch-voltage worksheet boundary
This page is not a human-response model, earthing design tool or work-method procedure. It records entered assumptions and exposes the arithmetic relationship between current, path impedance, voltage and threshold margin.
| Task | Use this page? | Better route when not this page |
|---|---|---|
| Estimate touch voltage from entered current and path impedance. | Yes. | Not applicable. |
| Estimate fault current from voltage and loop impedance. | No. | Fault loop impedance calculator. |
| Estimate prospective short-circuit current. | No. | Short-circuit current calculator. |
| Record earth electrode resistance assumptions. | No. | Earth electrode resistance calculator. |
| Compare protective conductor area with an entered requirement. | No. | Protective conductor check calculator. |
| Interpret manufacturer device behaviour. | No. | Manufacturer data and competent review. |
No safety conclusion
Touch-voltage records depend on the current source, earthing arrangement, bonding state, contact scenario, path impedance, duration basis, site controls and current Australian requirements. This worksheet keeps those assumptions visible, but it does not decide work methods, site controls, energisation state or personal risk.
Use the estimate as a transparent row in a broader project record. If the estimate is above the entered threshold, or if any input source is uncertain, keep the row open for competent-person review.
Stop points
- The current basis cannot be traced to the contact scenario.
- The path impedance is a guess rather than a recorded assumption.
- The entered threshold source is missing or unclear.
- Contact duration does not belong to the same scenario.
- The row is being used as a work-method or human-response conclusion.
Entered touch-voltage record
A protection worksheet records a 50 mA entered current and a 1000 ohm path impedance assumption for accessible metalwork.
- Worksheet reference
- TV-DB-1
- Contact scenario
- accessible metalwork
- Entered current
- 0.05 A
- Path impedance
- 1000 ohm
- Contact duration
- 0.2 s
- Entered threshold
- 50 V
- Estimated touch voltage50 V
- Threshold margin0 V
- Threshold utilisation100%
- Current-duration product0.01 A.s
Estimated touch voltage is at or below the entered threshold.
The estimated touch voltage equals the entered threshold, so the row remains an estimate record with the source basis visible.
- Current and path impedance are entered by the user.
- The touch-voltage threshold is entered by the user.
- The worksheet does not set a work method or human-response conclusion.
Threshold review
A temporary bonding worksheet uses a higher entered current with the same path impedance assumption.
- Worksheet reference
- TV-REVIEW
- Contact scenario
- temporary bonding review
- Entered current
- 0.08 A
- Path impedance
- 1000 ohm
- Contact duration
- 0.2 s
- Entered threshold
- 50 V
- Estimated touch voltage80 V
- Threshold margin-30 V
- Threshold utilisation160%
- Current-duration product0.016 A.s
Estimated touch voltage is above the entered threshold.
The estimated touch voltage is above the entered threshold, so the row needs project and source-basis review.
- The current source remains external to the calculator.
- The path impedance is an entered assumption.
- The page does not model human response.
Duration basis record
A test point estimate keeps contact duration visible while comparing voltage against the entered threshold.
- Worksheet reference
- TV-DURATION
- Contact scenario
- test point estimate
- Entered current
- 0.03 A
- Path impedance
- 1200 ohm
- Contact duration
- 0.5 s
- Entered threshold
- 50 V
- Estimated touch voltage36 V
- Threshold margin+14 V
- Threshold utilisation72%
- Current-duration product0.015 A.s
Estimated touch voltage is at or below the entered threshold.
The voltage comparison remains below the entered threshold, while the current-duration product is kept with the row.
- Duration is recorded as an exposure basis only.
- The entered threshold source remains external.
- Competent-person review can override the worksheet.