FT6041-91 - Earth Tester Set with Selective and Stakeless Testing

Key Specifications

• Earth resistance measurement: 2-pole, 3-pole and 4-pole
• FT9847 and CT9848 included for selective and stakeless earth testing 
• Soil resistivity measurement with 4-pole Wenner method 
• Separate 4-terminal resistance measurement 
• Optional Bluetooth communication with Z3210 

Typical Applications

• Selective earth resistance measurement in connected grounding systems
• Stakeless earth resistance measurement in multiple earthed systems
• Earth resistance measurement in electrical installations and industrial grounding systems 
• Soil resistivity measurement according to Wenner for grounding design and site surveys
• Continuity and resistance measurement between earth electrodes and installations 

Detailed Product Overview

The HIOKI FT6041-91 is an earth tester set for electrical professionals working in service, maintenance, inspection and grounding design. It combines 2-pole, 3-pole and 4-pole earth resistance measurement with soil resistivity measurement and separate 4-terminal resistance measurement in one instrument. With the included CT9848 Signal Detection Clamp and FT9847 Signal Induction Clamp, the set also supports selective earth resistance measurement, which HIOKI refers to as Measuring Earth with a Clamp (MEC), as well as stakeless earth resistance measurement. 

Rated IP67 for dust and water protection, the FT6041-91 includes test leads on reels, auxiliary earth spikes, earth nets modules, and the FT9847 and CT9848 clamps. This means the set covers conventional earth testing with auxiliary earth spikes as well as selective and stakeless methods. Measurements on concrete and other hard surfaces can also be carried out with the accessories included in the set. 

Measurement methods for earth resistance and soil resistivity

For checking the earth resistance of an existing earth electrode, the FT6041-91 provides a 3- pole method with two auxiliary earth spikes. In this setup, the earth electrode under test is disconnected from the installation for measurement. The test voltage can be switched from 30 V to 20 V in very wet conditions. If a full 3-pole setup is not possible or practical, the instrument also offers a simplified 2-pole method. In 2-pole measurement, the selectable test voltages are 8 V and 20 V. The measurement frequency can be set to 94 Hz, 105 Hz, 111 Hz, 128 Hz or 55 Hz to reduce the influence of noise or adapt the measurement to site conditions. 

For soil resistivity surveys, the FT6041-91 supports 4-pole measurement based on the Wenner method. The instrument measures resistance and calculates soil resistivity in Ω·m from the selected electrode spacing. In this mode, the test voltage can also be switched between 30 V and 20 V. Electrode spacing can be set from 1 m to 50 m in 0.1 m steps, or from 3 ft to 160 ft in 1 ft steps. 

Selective and stakeless measurements with clamps 

The FT6041-91 includes the CT9848 Signal Detection Clamp and the FT9847 Signal Induction Clamp for selective and stakeless earth resistance measurement. For selective earth resistance measurement, HIOKI uses the term Measuring Earth with a Clamp, or MEC. In this method, the CT9848 detects the measurement current of a specific earth electrode in a connected multiple earthed installation, so the electrode does not need to be disconnected for the test. Depending on the application, this can be carried out as a 3-pole or 4-pole measurement with clamp.

For stakeless earth resistance measurement, the FT9847 injects the test signal into the grounding conductor while the CT9848 senses the resulting current. This two clamp method is intended for multiple earthed systems and works without auxiliary earth spikes. Because both clamps are already included, the FT6041-91 covers both clamp based methods as part of the set. 

Resistance measurement and measurements on hard surfaces

The FT6041-91 also includes dedicated 2-terminal and 4-terminal resistance measurement. That is useful, for example, when an earth electrode has been disconnected for a 3-pole test and the connection needs to be checked after it has been reconnected. The 2-terminal mode is suited to basic continuity checks, while the 4-terminal mode minimizes the influence of lead resistance and allows more accurate low-resistance measurement of earth connections. In many cases, there is no need for a separate resistance meter.

The FT6041-91 includes two L9846 Earth Nets Modules. They are used where earth spikes cannot be inserted directly into concrete or other hard surfaces. After the modules are opened, two copper mesh contact areas are placed on the surface under test and moistened with water to establish electrical contact. The earth nets modules can be clicked onto the supplied test lead reels, forming a single assembly.

Bluetooth communication with Z3210 

Optional Bluetooth communication can be added to the FT6041-91 with the Z3210 Bluetooth Adapter. This allows measured values to be transferred wirelessly to Windows, iOS or Android devices. For smartphones and tablets, the free GENNECT Cross app is available for displaying, storing and documenting readings. Alternatively, the Z3210 can operate in HID mode, where measured values are sent to the active application as keyboard input. This allows direct data entry into Excel, text applications or custom software applications. 

Like all HIOKI earth testers, the FT6041-91 was developed in Japan and is manufactured at HIOKI’s own production facilities in Nagano Prefecture, Japan.