HIOKI FT6041-91 Earth Tester Set | With Clamp Sensors

When You Can’t Afford to Shut Down Power — And Still Need Compliant Earthing Results

Earthing compliance doesn’t pause for operational schedules. A data centre running 24/7 needs verified earth resistance values just as much as a construction site that can be temporarily de-energised. The challenge is that the standard approach to earth resistance testing — disconnecting the grounding electrode, running a 3-pole fall-of-potential test, and reconnecting — simply isn’t practical in many of the environments where it matters most.

Hospitals, pharmaceutical manufacturing, food processing plants, telecommunications exchanges, server facilities — in all of these settings, power interruption carries costs and risks that far outweigh the inconvenience of a non-compliant test report. Yet the earthing system still needs to be checked. It still needs to be documented. The results still need to hold up under scrutiny.

What changes the equation entirely is having the right clamp sensors in your kit.

The HIOKI FT6041-91 Earth Tester Set is the configuration built specifically for professionals who need live-system ground resistance testing capability from day one. It combines the field-proven FT6041 Earth Tester with both the FT9847 Signal Induction Clamp and CT9848 Clamp-On Sensor — the complete hardware pair required to activate the FT6041’s MEC function and 2-clamp measurement method, delivered together in a single purchase.

No additional accessories to source separately. No compatibility guesswork. Everything required to test live earthing systems is in the case.

What the FT6041-91 Includes — and Why Each Component Matters

HIOKI FT6041 Earth Tester (Main Unit)

The FT6041 is HIOKI’s flagship portable earth resistance tester. Rated IP67 for dust and water protection, drop-tested from 1 metre onto concrete, and rated for operation across -25°C to +65°C, it’s built for the kind of outdoor and industrial conditions found routinely across Australian electrical work. Six measurement methods are supported natively: 3-pole, 4-pole (Wenner’s soil resistivity), MEC function, 4-terminal low-value resistance, 2-clamp, and low-resistance continuity.

Measurement speed matters on multi-point testing programs — the FT6041 returns a full 3-pole reading in 6 seconds, with auto-hold capturing the value automatically. The included 100 kΩ maximum auxiliary electrode resistance tolerance means a single rod insertion is generally sufficient even in the dry sandy soils common across much of regional Australia, eliminating the frustrating cycle of repeated insertions and water pours.

The full measurement cable set is included: 25 m yellow, 25 m blue, and 50 m red winder cables plus a 4 m black lead and 1.2 m test lead. The winder mechanism is designed to retract cleanly without tangling — a detail that sounds minor until you’ve spent time managing 50 metres of cord on a busy site.

FT9847 Signal Induction Clamp

The FT9847 is the signal injection component of the MEC and 2-clamp measurement system. It clamps around the conductor connected to the earth electrode being tested and injects the FT6041’s test signal into that specific conductor — without any electrical contact required. The clamp jaw accommodates conductors up to 52 mm diameter and bus bars up to 78 mm × 20 mm, covering the range of earthing conductor cross-sections encountered in commercial and industrial installations.

The FT9847 is also used in the 2-clamp method, where it injects the measurement signal into a multi-electrode earthing network, enabling individual electrode resistance values to be determined without disconnecting the network.

CT9848 Clamp-On Sensor

The CT9848 is the current detection component. It measures the current flowing specifically through the target electrode conductor, allowing the FT6041 to calculate resistance from the known injected signal and the measured response current. With the same jaw capacity as the FT9847 (52 mm diameter / 78 mm × 20 mm bus bar), the CT9848 is designed with a thin jaw profile to work in tight busbar compartments and enclosed switchboard spaces where a standard clamp sensor simply won’t fit.

Together, the FT9847 and CT9848 enable the FT6041 to perform:

• MEC function (3-pole with clamp): Live-system earth resistance measurement without electrode disconnection or power interruption
• MEC function (4-pole with clamp): Live-system measurement with enhanced accuracy at low resistance values
• 2-clamp method: Individual electrode resistance measurement within parallel multi-ground networks

Without these sensors, these three measurement modes are unavailable. In the standard FT6041, they must be purchased separately. In the FT6041-91, they’re included as standard.

Six Measurement Methods — Covering Every Scenario in the Field

3-Pole Method (Standard Fall-of-Potential) The go-to approach for precise ground resistance verification on standard electrical installations. Accuracy of ±1.5% rdg. ±4 dgt. across the core 30–300 Ω range. Appropriate for installation commissioning and periodic compliance verification under AS/NZS 3000 and AS/NZS 3017.

4-Pole Method — Soil Resistivity (Wenner’s Method) Required for grounding system design on new builds, subdivisions, and infrastructure projects. Australian soil conditions are highly variable — coastal sandy soils, clay-heavy suburban environments, and rocky regional terrain all have very different resistivity profiles that directly determine what earthing electrode design will achieve compliant resistance values.

MEC Function — Live System Testing The defining capability of this kit configuration. By clamping the FT9847 and CT9848 around the earthing conductor, resistance can be measured on fully energised systems without disconnecting anything. The MEC function measures only the current flowing through the specific electrode under test, isolating it from parallel grounds in the same system. For any site that cannot tolerate power interruption, this capability removes the barrier to compliant earthing documentation.

3-Pole with 4-Terminal Measurement For grounding systems where target resistance values are very low — bonded structural steelwork, reinforced concrete foundations, or high-performance earthing grids — the 4-terminal variation of the 3-pole method delivers precision at sub-ohm levels where a standard 3-pole test becomes unreliable.

2-Clamp Method Multi-point earthing networks — common in industrial facilities, transmission infrastructure, and campuses with multiple buildings sharing an earthing grid — contain parallel electrode connections that affect each other’s apparent resistance. The 2-clamp method uses the FT9847 and CT9848 pair to inject and detect independently, allowing individual electrode values to be resolved within the network without any disconnection.

Low-Resistance Measurement Built-in continuity testing using 4-terminal or 2-terminal measurement, from 0.00 Ω to 3000 Ω. Confirms bonding conductor integrity immediately after ground resistance testing — one instrument handles the complete post-installation verification sequence.

Rugged Enough for Australian Conditions

The FT6041-91 is not a lab instrument that happens to go outside. Every aspect of the FT6041 main unit is designed for sustained outdoor use in demanding environments:

IP67 Dust and Water Protection — Fully sealed against dust ingress, rated to survive 1 metre water immersion. Rain, mud, and site dust are non-issues. If it gets dirty, wash it off with water.

-25°C to +65°C Operating Temperature — Australian summer conditions on exposed plant sites, combined with winter work in alpine or southern regions, push test instruments to their limits. The FT6041 operates correctly across this full range without performance compromise.

1 m Drop Resistance (with Protector) — Tested to withstand being dropped onto concrete from 1 metre with the included protector fitted. The kind of accidental drop that destroys an entry-level instrument won’t stop the FT6041.

30 V RMS Ground Potential Tolerance — Near distribution infrastructure or in industrial environments with significant stray potentials, the FT6041 maintains stable readings up to 30 V RMS ground potential. The live wire warning function activates automatically when ground potential is detected at the earth terminal.

Measure on Any Surface — Including Concrete: The L9846 Earth Nets Module (2× Included)

Here’s a scenario that catches a lot of electricians out: you’ve driven to a site, unpacked the gear, and the auxiliary electrode locations are solid concrete — a basement plant room, a rooftop plant deck, a warehouse slab. No soil access. Nowhere to drive a rod.

This is exactly what the HIOKI L9846 Earth Nets Module is designed for, and the FT6041-91 includes two of them as standard.

The L9846 is a foldable flat-surface auxiliary electrode with two integrated copper mesh contact pads, each measuring 18 × 22 cm. It features a magnetic latch that holds it closed during storage and transport, and clips directly onto the L9845-series cable reels included in this kit — so it travels as a single unit with the measurement cable, not as a separate item rattling around in your bag.

How it works in the field:

1. Unfold the L9846 and place both copper mesh faces flat against the concrete surface
2. Pour water through the built-in funnel on the attachment side — it distributes across the mesh via outlet slots on the opposite face
3. Connect via the alligator clip lead and measure

The water establishes conductivity between the copper mesh and the concrete surface, creating a usable auxiliary electrode contact without any drilling, hammering, or soil access required. Standard auxiliary rods back into the picture when you return to soil-accessible locations — the L9846 slides back onto the cable reel and stows away cleanly.

Important: The L9846 is also sold separately as a standalone accessory for $650 + GST. The FT6041-91 includes two L9846 modules as standard kit items — a meaningful inclusion that eliminates a separate purchase for any job that involves hard-standing measurement locations.

The L9846 is compatible with HIOKI cable reels L9845-31 (yellow, 25 m), L9845-33 (blue, 25 m), L9845-52 (red, 50 m), L9842-11 (yellow, 10 m), and L9842-22 (red, 20 m) — all of which are part of the standard FT6041-91 cable set.

Kit Contents — Everything Included

The FT6041-91 ships as a complete, ready-to-use kit:

APPLICATIONS

Facility Maintenance — Hospitals, Data Centres, and Critical Infrastructure

The FT6041-91 was built with this use case at its core. In 24/7 operational facilities, the MEC function is not a nice-to-have — it’s the only viable method for periodic earthing verification. The included FT9847 and CT9848 clamps allow maintenance electricians and electrical engineers to document earth resistance values for every electrode in the system without scheduling a shutdown, alerting operations, or risking service continuity. Compliance records get produced on time, every time, without operational disruption.

Industrial Plant — Continuous Process Manufacturing

Chemical plants, refineries, paper mills, and other continuous-process industrial facilities run on tight production schedules where unplanned shutdowns carry significant financial penalties. Earthing systems in these environments are also safety-critical — fault current paths depend on verified resistance values. The FT6041-91’s combination of MEC live-testing capability and 30 V RMS ground potential tolerance makes it the practical choice for industrial maintenance teams working around energised plant.

Multi-Electrode Commercial and Industrial Earthing Systems

Modern commercial buildings and industrial facilities often employ complex earthing arrangements — multiple electrodes, ring earths, structural steel bonding, and lightning protection systems all interconnected. Resolving individual electrode resistances within these parallel networks requires the 2-clamp method, which relies directly on the FT9847 and CT9848 sensors included in this kit. Without them, individual electrode values within the network simply cannot be determined without physical disconnection.

Solar PV and Renewable Energy Commissioning

Utility-scale and large commercial solar installations require verified earthing systems for both safety certification and grid connection approval. The FT6041-91 supports the full commissioning sequence: Wenner 4-pole soil resistivity surveys during design, 3-pole ground resistance verification at commissioning, and ongoing live-system checks using the MEC function during periodic maintenance — all without taking the inverter system offline.

Telecommunications and Critical Communications Infrastructure

Mobile base stations, exchange buildings, and microwave relay sites all rely on low-resistance earthing for both equipment protection and interference suppression. Many of these sites operate continuously and carry operational obligations that preclude routine power interruption. The FT6041-91’s clamp-sensor capability allows regular earthing verification to proceed without service disruption.

Electrical Contractor Pre-Handover and Periodic Testing

Even where live-system testing isn’t strictly required, the FT6041-91 kit gives electrical contractors maximum flexibility at handover and during periodic compliance inspections. Having the clamp sensors on hand means no measurement scenario presents a dead end — whether it’s a tight switchboard space where conventional test leads can’t reach, a system where the client is reluctant to approve power interruption, or a multi-electrode installation that requires individual electrode resolution.

WHY CHOOSE US FOR YOUR HIOKI FT6041-91

We supply HIOKI instrumentation from authorised Australian distribution channels, backed by technical support from a team with genuine electrical compliance and calibration expertise — not a generalist online store. When you order the FT6041-91 from us, you can expect:

• Genuine HIOKI product — not grey-market imports
• Pre-sales application advice — if you’re unsure whether the FT6041-91 or FT6041-92 KIT is right for your workflow, we’ll help you work it out before you buy
• NATA-accredited calibration — when your instrument is due for calibration and you need a certificate that stands up in a compliance audit, we can handle it
• Fast Australian dispatch — no waiting on international freight timelines for your core test instruments
• Ongoing technical support — from people who understand Australian earthing standards and compliance requirements, not just the product datasheet