ERT Series
ERT-15C & ERT-20C+
Clamp on, read the earth loop, move to the next electrode. No auxiliary rods, no disconnecting the down conductor, and on the C models a true RMS leakage current reading that tells you whether a high figure is a real fault or noise on the loop.
Where the ERT Series excels
Anywhere the earth is already bonded into a loop and taking it apart to test it is not an option.
Transmission & telecom towers
Lightning protection down conductors
Substations & distribution
PV arrays & bonded building grids
Flat steel earthing tape
Built for fast, repeatable surveys
No auxiliary electrodes
On a looped system the jaw injects and reads on the same conductor, so nothing has to be disconnected or driven into the ground.
0.001 Ω resolution
±(1% + 0.01 Ω) from 0.01 to 0.99 Ω, which is where earthing work is usually judged.
True RMS leakage current
0.0 mA to 20.0 A on the C models, so a high reading can be traced to a genuine fault or to loop interference.
99-reading memory
Store, recall and clear on the instrument, with an alarm threshold you set for resistance or current.
Interference indicator
A NOISE flag warns when loop current is corrupting the reading, so a doubtful figure is not recorded as a good one.
Test loop supplied
A nominal 5.1 Ω loop at 20 °C, for proving the instrument on site before the survey starts.
Round jaw or long jaw?
Both share the same measurement principle, keypad and memory. The difference is the shape of the opening, and that decides what you can get the instrument around.
Ø32 mm circular opening
- Takes round conductors up to 32 mm across
- Resistance 0.01 to 200 Ω, no current measurement
- Shortest and lightest of the range at 260 mm and 1120 g
- Suits earth rods, round down conductors and tower legs
- Best where access is tight and the reading is expected to be low
65 × 32 mm elliptic opening
- Swallows flat earthing tape up to 65 mm wide
- Resistance 0.01 to 1200 Ω plus leakage current to 20 A
- RS232 upload with software on the ERT-20C+
- Suits substation earth bars, tape-bonded grids and multi-core bundles
- Best where you also need to see the current flowing in the earth
Note the round jaw takes the wider round conductor: the long jaw spans 65 mm across the flat but only 28 mm through the round axis. If you are clamping cable rather than tape, check the diameter before choosing.
Technical specifications
| Models | ERT-15C, ERT-20C, ERT-20C+ |
|---|---|
| Measurement | Earth loop resistance · leakage and neutral current on C models |
| Resistance range | 0.01 to 200 Ω (ERT-15C) · 0.01 to 1200 Ω (ERT-20C, ERT-20C+) |
| Current range | 0.0 mA to 20.0 A, true RMS – ERT-20C and ERT-20C+ |
| Jaw | Round Ø32 mm (ERT-15C) · long elliptic 65 × 32 mm (ERT-20C, ERT-20C+) |
| Alarm | Resistance 1 to 199 Ω · current 1 to 499 mA · audible and visual |
| Memory | 99 readings, retained through power off |
| Data upload | RS232 with software – ERT-20C+ only |
| Test frequency | Resistance above 1 kHz · current measured at 50/60 Hz |
| Safety | IEC/EN 61010-1 and 61010-2-032 · CAT III 150 V to earth, 20 A maximum |
| Protection | Double insulated · pollution degree II · IP30 · IK04 |
| Display | 4-digit LCD with backlight, sign and decimal point · automatic ranging |
| Power | 4 × 1.5 V LR6 AA alkaline · below 50 mA · auto power off after 5 minutes |
| Dimensions | 260 × 90 × 66 mm, 1120 g (ERT-15C) · 285 × 90 × 66 mm, 1160 g (ERT-20C/C+) |
| Environment | Operating −10 to 55 °C, 10 to 90% RH · storage −20 to 60 °C |
What’s in the box
- ERT main unit, model as ordered
- Test loop for on-site verification
- Carrying case
- User manual
Need pricing or a spec check?
Tell us the conductor and we’ll tell you which jaw fits, with pricing and lead time.
Accuracy across the range
Accuracy is tightest at the low end, where earthing is normally judged, and widens towards the top of the range. Published in full so you can see where the instrument is definitive and where it is indicative.
| Resistance range | Resolution | Accuracy |
|---|---|---|
| 0.010 to 0.099 Ω | 0.001 Ω | ±(1% + 0.01 Ω) |
| 0.10 to 0.99 Ω | 0.01 Ω | ±(1% + 0.01 Ω) |
| 1.0 to 49.9 Ω | 0.1 Ω | ±(1% + 0.1 Ω) |
| 50.0 to 99.5 Ω | 0.5 Ω | ±(1.5% + 0.5 Ω) |
| 100 to 199 Ω | 1 Ω | ±(2% + 1 Ω) |
| 200 to 395 Ω | 5 Ω | ±(5% + 5 Ω) |
| 400 to 590 Ω | 10 Ω | ±(10% + 10 Ω) |
| 600 to 880 Ω | 20 Ω | ±(20% + 20 Ω) |
| 900 to 1200 Ω | 30 Ω | ±(25% + 30 Ω) |
| Current range | Resolution | Accuracy |
|---|---|---|
| 0.00 to 9.00 mA | 0.05 mA | ±(2.5% + 2 mA) |
| 10.0 to 99.0 mA | 0.1 mA | ±(2.5% + 10 mA) |
| 100 to 300 mA | 1 mA | ±(2.5% + 20 mA) |
| 0.30 to 2.99 A | 0.01 A | ±(2.5% + 0.1 A) |
| 3.0 to 9.9 A | 0.1 A | ±(2.5% + 0.5 A) |
| 10.0 to 20.0 A | 0.1 A | ±(2.5% + 1 A) |
Resistance rows above 200 Ω apply to the ERT-20C and ERT-20C+ only. Current measurement is on the C models. These instruments read the resistance of a closed loop: a single isolated electrode has no loop, and is measured by bonding it to a second known-good electrode, or by the three-point method set out in the user manual.