VRF Transmission Cable Resistance Check
Use this check to assess the resistance of the VRF transmission cable. The measured resistance should correspond with the approximate cable distance from the termination resistor.
Key point: As transmission cable length increases, the expected resistance also increases. Use the measured resistance together with the approximate distance to the termination resistor to assess the network.
Approximate resistance by cable distance
| Distance from termination resistor | Approximate resistance range | Assessment |
|---|---|---|
| 0–100 m | Approx. 50–75 Ω | Normal range shown by the reference chart |
| ~200 m | Approx. 65–105 Ω | Normal range shown by the reference chart |
| ~300 m | Approx. 80–135 Ω | Normal range shown by the reference chart |
| ~400 m | Approx. 85–155 Ω | Normal range shown by the reference chart |
| ~500 m | Approx. 95–180 Ω | Normal range shown by the reference chart |
Fault indication
0–50 Ω
A short circuit may be present, or two or more termination resistors may be connected.
A short circuit may be present, or two or more termination resistors may be connected.
190 Ω or higher
Indicates a faulty contact or transmission wiring length over 500 m.
Indicates a faulty contact or transmission wiring length over 500 m.
1 kΩ to ∞
Indicates a faulty contact, an open circuit, or no termination resistor.
Indicates a faulty contact, an open circuit, or no termination resistor.
How to interpret the reading
| 1 | Measure the transmission cable resistance using the applicable service procedure. |
| 2 | Estimate the distance from the test point to the termination resistor. |
| 3 | Compare the measured resistance with the corresponding range above. |
| 4 | If the reading is in one of the fault ranges, investigate the transmission wiring, connections and termination resistor arrangement. |
Note: The resistance values shown are approximate and are intended to be interpreted against the transmission cable length. Always refer to the applicable VRF service documentation for the specific system being tested.