LTW300 series

Two-wire non-tripping loop impedance testers

  • Two-wire non-tripping loop tester
  • 50 V to 440 V operation
  • 110 V centre-tap loop testing
  • CAT IV installation testing
  • Auto start operation
  • 0.01 Ω resolution

The LTW300 two-wire non-tripping loop impedance testers verify the loop impedance of a live electrical circuit, i.e., without the need to disconnect the electrical supply. The new LTW300 series instruments offer a two-wire loop testing solution that does not trip 30 mA RCDs and can be used on a wide range of voltages.

The new LTW300’s offer a range of features to make earth loop testing safer and easier. The range consists of:

  • LTW315: two-wire loop impedance measurement
  • LTW325: two-wire + maxZ + (R1+R2)
  • LTW335: two-wire + maxZ + (R1+R2) + download

The LTW300 series of instruments are guaranteed not to trip working RCDs of ≥30 mA, using the no-trip loop test. Three-phase circuits with RCD protection can also be tested, as all test modes operate on single and three phase systems. The loop test runs for approximately 10 seconds, with an additional 10 seconds if the instrument detects electrical noise on the supply that could otherwise cause errors on the test result.

For supplies that do not have an RCD fitted, the high current test should be used, as there is no risk of tripping and RCD. Noise detection (only applies to no-trip tests).

The LTW300 also uses sophisticated noise detection circuitry which continually monitors the supply whilst performing a loop test to ensure the accuracy of the result has not been compromised by the effects of electrical noise from plant and services

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Technical Documents
Technical guide
Instrument category rating
Technical guide
Loop testing techniques
Technical guide
Testing on 110 V systems
Technical guide
Testing three-phase systems
Technical guide
Use of fused test leads