KYORITSU KEW 4105DLBT-H: What This Bluetooth Earth Resistance Tester Is, and Who Actually Needs the Hard-Case Model

If you landed here searching "KEW 4105DLBT-H," you probably saw the model number on a job-site instrument, a distributor listing, or an eBay title, and want to know what it actually does before spending on it. Short answer: it's a digital earth (ground) resistance tester from KYORITSU, Japan's clamp-meter and multimeter maker, built to run the standard 3-pole fall-of-potential ground test and stream the reading to a phone over Bluetooth. It's not a multimeter and it's not a simple continuity checker — it's a dedicated instrument for verifying that a grounding electrode is actually doing its job, which matters for anyone signing off on an electrical installation or a periodic safety inspection. This post covers what the 3-pole measurement actually checks, who realistically needs the Bluetooth hard-case version versus the cheaper alternatives in Kyoritsu's own lineup, and whether ordering it from Japan makes sense.

KYORITSU KEW 4105DLBT-H, hard case set (photo from the eBay listing)

What a 3-pole earth resistance tester actually measures

The core function is the "fall-of-potential" test defined in IEC 60364-6: you drive two auxiliary earth spikes into the ground at set distances from the electrode being tested, the instrument pushes a small current through the earth path via one spike, and measures the resulting voltage drop through the other to calculate the electrode's actual resistance to true earth. This 3-pole method is the one that produces a number you can put on an inspection certificate, as opposed to the 2-pole "simplified" mode, which just compares the electrode against a known reference ground (useful for a quick recheck, not for a first-time verification). The 4105DLBT-H's specific contribution on top of that measurement is Bluetooth 5.0 streaming to the KEW Smart Advanced app — worth being precise here, since it's easy to assume a "Bluetooth model" logs data internally. It doesn't: this unit has no built-in memory or data-hold function, so the app is the only place a reading gets recorded, which means the phone (not the meter) is doing the record-keeping. Add in an IP67 rating that lets you literally rinse mud off the case after a job, a backlit LCD with a rotary-switch interface, and a red warning LED that lights if stray earth voltage is detected during the test, and the instrument is built around one use case: getting an accurate ground reading outdoors, on a real job site, and getting that number onto a phone without transcribing it by hand.

Who actually needs the Bluetooth hard-case model

The realistic buyer is an electrician or maintenance technician doing 3-pole ground verification as part of an actual documented process — new-installation grounding checks against IEC 60364-6 or an equivalent local code, solar and EV-charger installers confirming a grounding electrode system meets spec before sign-off, and industrial or facilities electricians running scheduled periodic checks on switchgear, generator grounds, or lightning-protection systems where a written record of the reading matters. The Bluetooth piece specifically earns its keep for anyone who'd otherwise be copying numbers from an LCD into a paper log or a phone note by hand — the KEW Smart Advanced app turns that into photographing or exporting the reading directly. That said, it's worth being honest about when this exact configuration is overkill. If you only need an occasional rough check against a known reference — not a certifiable 3-pole measurement — Kyoritsu's own simplified 2-pole-only testers, like the KEW 4300, are cheaper and simpler for that narrower job. And if you don't care about phone connectivity at all, the non-Bluetooth KEW 4105DL-H runs the identical 3-pole measurement, with the identical accuracy specs, for less money — the DLBT-H is specifically for people who want that reading on a phone, not just on the LCD.

Is there a reason to buy this from Japan specifically?

Kyoritsu isn't an obscure name to anyone who's worked with test equipment — the company set up a US sales channel back in 1957 after an inquiry from the US Department of Commerce, and by 1965 the KEW brand was already sold in more than 60 countries. That history matters here because it means the brand carries real recognition among electricians and test-equipment buyers, not just goodwill inside Japan. Where it gets more complicated is the specific product category and configuration. In the US, ground-resistance testing equipment on the shelf at electrical-supply houses and industrial distributors is dominated by Fluke, Megger, and AEMC — mainstream distributors like Grainger don't stock Kyoritsu earth testers as a regular line. The 4105DLBT-H does turn up on Amazon.com and Amazon.co.uk, but under third-party "Japan Quality"-branded reseller listings rather than an official Kyoritsu USA storefront, which means there's no dedicated authorized-distributor warranty or support path backing that specific listing. At roughly 690g including the hard case, it's light enough that international shipping doesn't eat deeply into any price advantage the way it would with a heavier tool. So the honest framing is: if you want the shortest path to US-based support and don't mind paying a reseller markup, the Amazon listings exist; if price is the deciding factor and you're comfortable buying directly from a Japan-based seller, that's a real gap worth comparing rather than a case where "just buy it locally" is obviously the better answer.

Specifications (measurement methods, ranges, accuracy, standards, communication interface, dimensions, weight, and included accessories) were sourced directly from KYORITSU's official English-language product page for the KEW 4105DLBT-H (kew-ltd.co.jp/en/products/detail/01316/), cross-checked against the related-model pages for the KEW 4105DL-H (detail/01283/) and KEW 4105DLBT (detail/01361/) to confirm which features (Bluetooth, case type) differ between the three. Company history and founding dates were sourced from KYORITSU's official corporate History and Company Data pages (kew-ltd.co.jp/en/company/history/ and /company/data/). The claim that mainstream US distributors do not stock this model, and that current Amazon US/UK listings are third-party reseller listings rather than an official Kyoritsu USA storefront, was checked via web search of Amazon.com, Amazon.co.uk, and general distributor search results as of August 2026; this does not rule out the existence of a dedicated Kyoritsu USA channel not surfaced by that search. Country of manufacture was not stated on the sourced product page and is not claimed in this article. Figures reported only by unverified secondary sources were not used.