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The equation for translating the voltage into a resistance reading is shown below.
EQUATION 1: 
Where V713pxA is the nominal circuit voltage (12 V)
and VISO is the standing voltage between circuits measured by the SA380-IT
For Reference, a table is provided at the end of this document to enable the operator to quickly look up a value.
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The equation for translating the voltage into a resistance reading is shown below.
EQUATION 2: 
Where VA is the nominal circuit voltage of the 1st circuit (12 V)
and VB is the nominal circuit voltage of the second circuit(12 V)
and VISO is the standing voltage between circuits measured by the SA380-IT.
| Info |
|---|
Fault 3 and Fault 4 cause a larger voltage to be presented to the SA380-IT than Fault 1 and Fault 2. All four faults can also present in any combination, however the voltages presented in the case of Fault 1 and Fault 2 represent a "worst case" Equation 1 should therefore be used for the selection of alert levels and used to inform intervention decisions. The value yielded by equation 1 should there be read as "Resistance greater than or equal to X" Equation 1 also assumes a nominal circuit voltage. A voltage of 11.4 volts has been used to produce the table below. If it is credible that the cell voltage could fall further, yet the circuit remains operable, then a different nominal voltage should be used to populate the table. |
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If the wiring diagram above has been followed, the SA380-IT inputs should be configured as per the table below:
| Input No. | Name | Voltage | Type |
|---|---|---|---|
| 1 | B12 | 12 | DC |
| 2 | ISO 1 | 24 | DC |
| 3 | ISO 2 | 24 | DC |
| 4 | XB12 | 12 | DC |
Fault Resistance Table
Use the look up table below to convert the voltage present on wither the "ISO 1" or "ISO 2" channels into a worst-case level of inter-circuit isolation.
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The resistance value stated is "worst-case" the true level of isolation resistance may be greater and will be dependant upon how the fault is manifest.
Measured Voltage (ISO 1 or ISO 2) | Insulation Resistance (>= k Ohm) |
|---|---|
| 0 | INF |
| 0.1 | 31866 |
| 0.2 | 15792 |
| 0.3 | 10434 |
| 0.4 | 7755 |
| 0.5 | 6148 |
| 0.6 | 5076 |
| 0.7 | 4311 |
| 0.8 | 3737 |
| 0.9 | 3290 |
| 1 | 2933 |
| 1.1 | 2641 |
| 1.2 | 2397 |
| 1.3 | 2191 |
| 1.4 | 2014 |
| 1.5 | 1861 |
| 1.6 | 1727 |
| 1.7 | 1609 |
| 1.8 | 1504 |
| 1.9 | 1410 |
| 2 | 1325 |
| 2.1 | 1249 |
| 2.2 | 1179 |
| 2.3 | 1116 |
| 2.4 | 1058 |
| 2.5 | 1004 |
| 2.6 | 954 |
| 2.7 | 909 |
| 2.8 | 866 |
| 2.9 | 827 |
| 3 | 790 |
| 3.1 | 755 |
| 3.2 | 723 |
| 3.3 | 692 |
| 3.4 | 664 |
| 3.5 | 637 |
| 3.6 | 611 |
| 3.7 | 587 |
| 3.8 | 564 |
| 3.9 | 542 |
| 4 | 522 |
| 4.1 | 502 |
| 4.2 | 483 |
| 4.3 | 466 |
| 4.4 | 449 |
| 4.5 | 432 |
| 4.6 | 417 |
| 4.7 | 402 |
| 4.8 | 388 |
| 4.9 | 374 |
| 5 | 361 |
| 5.1 | 348 |
| 5.2 | 336 |
| 5.3 | 325 |
| 5.4 | 313 |
| 5.5 | 303 |
| 5.6 | 292 |
| 5.7 | 282 |
| 5.8 | 272 |
| 5.9 | 263 |
| 6 | 254 |
| 6.1 | 245 |
| 6.2 | 237 |
| 6.3 | 228 |
| 6.4 | 220 |
| 6.5 | 213 |
| 6.6 | 205 |
| 6.7 | 198 |
| 6.8 | 191 |
| 6.9 | 184 |
| 7 | 177 |
| 7.1 | 171 |
| 7.2 | 165 |
| 7.3 | 158 |
| 7.4 | 152 |
| 7.5 | 147 |
| 7.6 | 141 |
| 7.7 | 136 |
| 7.8 | 130 |
| 7.9 | 125 |
| 8 | 120 |
| 8.1 | 115 |
| 8.2 | 110 |
| 8.3 | 105 |
| 8.4 | 101 |
| 8.5 | 96 |
| 8.6 | 92 |
| 8.7 | 88 |
| 8.8 | 83 |
| 8.9 | 79 |
| 9 | 75 |
| 9.1 | 71 |
| 9.2 | 67 |
| 9.3 | 64 |
| 9.4 | 60 |
| 9.5 | 56 |
| 9.6 | 53 |
| 9.7 | 49 |
| 9.8 | 46 |
| 9.9 | 43 |
| 10 | 39 |
| 10.1 | 36 |
| 10.2 | 33 |
| 10.3 | 30 |
| 10.4 | 27 |
| 10.5 | 24 |
| 10.6 | 21 |
| 10.7 | 18 |
| 10.8 | 16 |
| 10.9 | 13 |
| 11 | 10 |
| 11.1 | 8 |
| 11.2 | 5 |
| 11.3 | 2 |
| 11.4 | 0 |
| 11.5 | 0 |
| 11.6 | 0 |
| 11.7 | 0 |
| 11.8 | 0 |
| 11.9 | 0 |
| 12 | 0 |