EM4058 Earth resistance meter

EM4058 — smart earth tester with multi-frequency

The EM4058 is a digital, microprocessor-controlled earth tester for measuring earth resistance and soil resistivity (Wenner’s method), as well as detecting parasitic voltages in the soil. The instrument is suitable for earth systems in substations, industry, distribution networks and more, in accordance with IEC 61557-5.

What makes the EM4058 unique is its multi-frequency measurement: the test frequency can be set to 270, 570, 870, 1,170 or 1,470 Hz. The lowest frequency analyses the earth system behaviour during industrial fault currents, while the highest frequency assesses behaviour during lightning strikes and offers maximum immunity against interference voltages near substations.

The Frequency Scan function automatically measures at all available frequencies and calculates the average result alongside the individual results per frequency.

Applications

• Substations and high-voltage networks — earth resistance measurement of grounding systems in accordance with IEC 61557-5
• Lightning protection systems — verification of earth electrodes and lightning conductors
• Industrial installations — verification of factory and machine earthing
• Distribution networks — periodic inspection of earthing at transformer stations and distribution boards
• Soil resistivity survey — Wenner’s method for designing and optimising earthing systems
• Telecom and data centres — earthing verification for sensitive electronic systems
• Stray voltage detection — measurement of parasitic voltages in the ground using the voltmeter function

Key features

• Earth resistance — 0.01 Ω to 20 kΩ, auto-ranging, 4 measurement ranges
• Soil resistivity (Wenner) — up to 50 kΩm, automatic calculation using Wenner’s full equation
• 5 measurement frequencies — 270, 570, 870, 1,170 and 1,470 Hz, user-selectable
• Frequency Scan — automatic measurement at all frequencies with average calculation
• Parasitic voltage measurement — 0–60 V AC voltmeter function
• High interference immunity — up to 7 V AC spurious voltage, error < 10%
• Accuracy — ± 2% (≤ 2 kΩ), ± 5% (> 2 kΩ)
• Built-in thermal printer — direct printout of measurement results in the field
• Memory — storage of measured values with date/time
• BlueLogg Android app — wireless control via Bluetooth
• USB interface — data transfer to PC
• IP65 enclosure — dust and waterproof, only 3 kg
• Rechargeable LFP battery — LiFePO4 12 V, 3,000 mAh, approx. 2,000 charge cycles
• Automatic fault detection — checks for low battery, excessive interference, high test spike resistance
• Compliant with IEC 61557-5 — CE, IEC 61010-1, IEC 61326-1
• 2-year warranty — standard Megabras factory warranty

Multi-frequency measurement

The EM4058 offers 5 selectable measurement frequencies. This is a significant advantage over single-frequency earth testers:

• 270 Hz — analyses the earth system during industrial fault currents (closest to 50 Hz), also suitable for soil resistivity
• 570–1,470 Hz — higher frequencies provide better insight into behaviour during lightning strikes and offer superior immunity against interference voltages near substations
• Frequency Scan — automatic measurement at all frequencies, calculates and prints the average plus individual results

MegaLogg 3 and BlueLogg

The EM4058 supports the BlueLogg Android app for wireless control via Bluetooth — including remote control, live measurement display and GPS location. Via USB, data transfer to a PC is possible using MegaLogg 3 software.

When to choose the EM4058, MTD20KWR or TM25T?

The EM4058 is the multi-frequency earth tester: 5 frequencies, Wenner’s method, Frequency Scan, ideal for comprehensive earth system inspections and soil surveys. For a compact earth resistance meter for standard inspections, the MTD20KWR is a budget-friendly alternative. For high-frequency earth resistance measurement at 25 kHz, see the TM25T.