Delmhorst BDX-20 Moisture Meter Behind the Wall Package

The Delmhorst BDX-20 Behind the Wall Package includes the meter, the 21-E deep wall electrode and a carrying case.

The Delmhorst BDX-20 is the latest in Delmhorst's long-running BD series of pin moisture meters for building inspectors, flooring installers, builders and water damage technicians. It measures timber from 6% to 60% moisture content and drywall from 0.1% to 6%, and has a reference scale for other building materials. It replaces the Delmhorst BD-2100.

The meter has an easy-grip handle, large tactile buttons and a custom backlit LCD with a simple menu, so readings are quick to take and easy to read on site.

What is in this package

• BDX-20 meter with integral contact pins
• 21-E deep wall electrode, 3 in penetration (our 21-E listing gives 3.25 in)
• Sturdy plastic carrying case
• 2 × AA Energizer alkaline batteries

The 21-E reads inside a wall cavity through a small drilled hole instead of only at the surface. For an inspector, that is the difference between reporting that the plasterboard is damp and confirming whether the framing behind it is. If you only need surface readings, the BDX-20 meter and case costs less, and you can add a 21-E later.

Features

The BDX-20 has 3 built-in measurement scales – Wood (Douglas Fir 6%–60%), Reference Scale (0–100) and Drywall (0.1%–6%). It uses the same meter body and core functions as the BDX-30 but has no Bluetooth, so it does not work with the EDGE™ app.

• Large, custom display with auto backlight – easy to read under all conditions.
• 3 measurement scales:
  • 6%–60% Wood (Douglas Fir)
  • 0.1%–6% Drywall
  • 0–100 Reference scale
• Wood temperature correction (°F/°C)
• Alarm set point – alerts at a user-selected MC level
• On-screen reading statistics – High, Low, Average, Standard Deviation, Last 10
• Internal calibration check
• Pins/electrode correction (insulated or non-insulated)
• Integral contact pins, max 5/16" (7.9 mm) penetration (replacement pins: 2498/A-100)
• Compatible with any Delmhorst external electrode
• Colour-coded LEDs
• Sturdy plastic carrying case – included
• Power – 2 × AA batteries – Alkaline Energizer included
• "Low Batt" warning with audio
• Auto-off timer, set to 1, 4 or 10 minutes
• QR code on meter for easy access to support materials

BDX-20 or BDX-30?

Both meters cover the same wood, drywall and reference ranges, and use the same pins, electrodes and temperature correction. They differ in species correction and record keeping:

If you write readings into your own reports or job system, the BDX-20 does the measuring job. If you want each reading logged with a date and location straight from the meter, or you regularly test species outside the built-in corrections, choose the BDX-30.

Specifications

Earlier versions of this page gave the meter's size and weight as "2.2mm" and "1.3g" and its depth as 39 mm (1.55 in). Those were errors; the figures above are from the Delmhorst owner's manual.

Operating advice

• Run the internal calibration check before each job. The manual gives a pass reading of 11.8 to 12.2; outside that, replace the batteries and check again.
• Select the correct scale for the material before reading. A drywall reading taken on the wood scale, or the reverse, means nothing.
• Set the pin correction to match what you are using – the integral pins and most electrodes are non-insulated; insulated pins read only at the tip, which is what lets you find the wet layer at depth.
• For timber, enter the material temperature so the temperature correction is applied.
• Test in the same places on each visit so a drying or acclimatisation trend means something.

Replacement pins

• Integral meter pins: 2498/A-100 pins with retainer
• 21-E deep wall probe: 608 insulated pin, 82.5 mm or 608/001 insulated pin, 152 mm

For every other Delmhorst pin and retainer, see the Delmhorst Contact Pins and Retainers Guide (PDF).

Frequently asked questions

Pin meter or pinless — which do I need?

The BDX-20 is a pin meter. It measures electrical resistance between two pins, giving a moisture content figure at a known depth, so you can trace where moisture sits in a structure. A pinless meter scans without marking the surface, but reads only near the surface and gives a relative indication. Many inspectors carry both.

Does it leave holes?

Yes. The integral pins leave two small marks, and electrodes leave larger ones. On finished surfaces, take readings somewhere out of sight — inside a cupboard, under a skirting board or behind furniture.

Can I read timber species other than Douglas Fir?

Yes. The BDX-20 has 3 built-in corrections. For other species, read on the Douglas Fir scale and apply a correction table — the owner's manual has one, and for Australian timbers see our Australian Timber Species Correction Tables and the general Correction Tables. If you do this often, the BDX-30 stores more corrections and removes the manual step.

Can I use my existing electrodes?

Yes. Every current Delmhorst meter accepts every Delmhorst electrode, so a 21-E or 26-ES from an older meter works on the BDX-20.

Can I upgrade a BDX-20 to Bluetooth later?

No. Bluetooth is built into the BDX-30 only. If you think you will want app records, buy the BDX-30.

Support and warranty

The Moisture Meter Company (Aberford Holdings Pty Ltd) is the exclusive Australian distributor for Delmhorst non-agricultural moisture meters. Service, calibration questions and warranty claims are handled here rather than sent overseas.

2-year warranty on manufacturer's defects. Bonus extended warranty with online registration. This does not exclude, restrict or modify your rights under the Australian Consumer Law.

Documents

• Delmhorst quick start guide (PDF)
• BDX-20 and BDX-30 owner’s manual, 05.2024 (PDF)
• Tether attachment guide for BDX series meters (PDF)
• BDX series brochure (PDF)

Not sure whether the BDX-20, the BDX-30 or a package with electrodes suits your work? Tell us what you are testing — timber floors, wall cavities, plasterboard, cladding — and we will recommend what you need. See the full range in Delmhorst Moisture Meters.