Deep wall probe for cavities and insulation
A two-pin probe with long insulated 608 pins, for reading moisture inside a wall cavity, behind stucco or under roofing without opening the structure up.
Why the insulation matters here
On the way to the insulation the pins pass through plasterboard, an air gap and whatever else is in the cavity. An uninsulated pin would report the wettest of all of it and you would not know which. The 608 pins are bare only at the tip, so the reading belongs to the depth the tip has reached.
Fitment
- Connects to any Delmhorst meter with an external electrode socket, including the BDX-30 and BDX-20
- Fitted with 608 insulated contact pins — up to 3 1/4 inch (82.6 mm) penetration
- Uses the 305RET-0021 pin retainer
- Uses the 315CAB-0025 cable assembly
Specifications
| Model | 21-E |
|---|---|
| Pins | 608, Teflon insulated except at the tip |
| Maximum penetration | 3 1/4 inches (82.6 mm) |
| Applications | Insulation behind drywall, stucco, roofing materials |
Choosing between the variants
- 21-E — 608 pins, 3 1/4 inch penetration. This listing.
- 21-ET — same pins, tapped handle so an extension pole can be fitted for high or awkward areas.
- 21-E/001 and 21-ET/001 — fitted with the longer 608/001 pins for deeper cavities. Not currently stocked; ask us.
Frequently asked questions
Does it leave a hole?
Two small pin holes in the surface, which is the point — it is the least invasive way to find out what is happening in a cavity.
Can I read the moisture content of insulation itself?
Resistance meters are calibrated for wood. In insulation, treat the reading as comparative — wetter or drier than the reference area — rather than an absolute moisture content.
Will it reach through a double-layer wall?
Maximum penetration is 3 1/4 inches. For deeper cavities you need the /001 variant with the longer pins.
Not sure which part suits your meter? Tell us the model and what you are testing and we will confirm the right one before you order.
