Correction Tables
Why corrections are needed
Resistance (pin-type) moisture meters do not measure moisture directly. They measure electrical resistance between two pins and convert it to a moisture content reading using a calibration curve. Delmhorst calibrates its meters to Douglas Fir, the USDA reference species.
Two things change that relationship in the field: the species of timber, and its temperature. Meters with species and temperature settings built in apply these corrections for you. Older meters, and simpler models, do not — on those the correction has to be applied manually to the reading.
If your meter has species and temperature compensation built in, set it correctly and ignore these tables. They are for meters that don't.
Species corrections
Because the electrical characteristics of different species vary, all species read differently at the same moisture content. Delmhorst uses Douglas Fir as the basis for all wood calibrations, so a correction is required for any other species.
Readings in the Delmhorst species table are taken with the 26-E two-pin electrode using insulated pins. Do not apply the pin correction below as well — the species table already accounts for it.
The SPF correction is based on USDA/Forintek data and can be used for Lodgepole Pine, Alpine Fir, Eastern White Spruce, Black Spruce and Jack Pine.
For Australian timbers, use our Australian Species Correction Tables instead. The Delmhorst species table covers North American species and will not give you a reliable result on Australian hardwoods.
Download the Delmhorst species correction table (PDF)
Temperature corrections
As wood temperature increases its electrical resistance falls, and the indicated moisture content rises. Lower temperatures produce lower indicated readings.
If the wood temperature — usually the same as ambient — is between 10°C and 32°C, no correction is needed.
Find your wood temperature in the left-hand columns, read across to the column matching your meter reading, and use the corrected figure.
| °C | °F | 6 | 7 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 50 | 60 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| -20 | 0 | 9 | 11 | 15 | 22 | 31 | 38 | 45 | 53 | |||
| -10 | 20 | 8 | 10 | 14 | 20 | 28 | 34 | 40 | 47 | 55 | ||
| 5 | 40 | 7 | 8 | 12 | 18 | 24 | 30 | 36 | 42 | 48 | ||
| 15 | 60 | 6 | 7 | 11 | 16 | 21 | 27 | 32 | 38 | 43 | 54 | |
| 30 | 80 | 6 | 7 | 9 | 14 | 19 | 23 | 28 | 33 | 38 | 47 | 55 |
| 40 | 100 | 5 | 6 | 8 | 12 | 17 | 21 | 25 | 29 | 34 | 42 | 50 |
| 50 | 120 | 5 | 5 | 7 | 11 | 15 | 19 | 22 | 26 | 30 | 38 | 44 |
| 60 | 140 | 4 | 5 | 7 | 10 | 14 | 17 | 20 | 23 | 27 | 34 | 40 |
| 70 | 160 | 4 | 4 | 6 | 9 | 12 | 15 | 18 | 21 | 24 | 30 | 36 |
| 80 | 180 | 3 | 4 | 5 | 8 | 11 | 13 | 16 | 19 | 22 | 27 | 33 |
| 95 | 200 | 3 | 4 | 5 | 7 | 10 | 12 | 14 | 17 | 19 | 24 | 28 |
| 105 | 220 | 2 | 3 | 4 | 6 | 9 | 11 | 13 | 15 | 17 | 21 | 26 |
Values shown in bold are above the fibre saturation point (30% MC) and are qualitative only. Treat them as an indication that the timber is wet, not as a precise figure.
Download the temperature correction table (PDF)
Pin corrections
Delmhorst pin meters are calibrated using non-insulated pins penetrating 5/16 inch. Insulated pins read slightly lower than non-insulated pins, so a correction is needed when using an insulated electrode such as the 26-ES.
| Meter reading with insulated pins | 7 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 |
|---|---|---|---|---|---|---|---|---|---|---|
| Corrected reading (true moisture content) | 7.3 | 8.4 | 10.6 | 12.8 | 14.9 | 17.0 | 19.2 | 21.4 | 23.7 | 26.0 |
Download the pin correction table (PDF)
Specific gravity corrections for pinless meters
Readings from pinless (capacitance) meters such as the Delmhorst TechScan or Wagner Orion are strongly influenced by the specific gravity of the timber. Wood with a higher specific gravity produces a higher reading than lower-density wood at the same moisture content.
The Delmhorst TechScan is calibrated for wood at a specific gravity of 0.46. A correction is required when measuring species with an SG other than 0.46. Refer to your meter's owner's manual for the correction method — it varies by model.
Download the specific gravity chart and species list (PDF)
Order of operations
Where more than one correction applies, work in this order:
- Take the reading.
- Apply the temperature correction.
- Apply the species correction to the temperature-corrected figure.
Applying them the other way round will give a different answer.
Not sure which correction applies to your meter, or whether your model compensates automatically? Contact Carpet Cleaners Warehouse before you rely on a reading — it takes a minute to check and it is cheaper than a callback.
