Bessemeter makes two pinless moisture meters that look nearly identical on paper: the D300 and the DS500. Both read from 6%–32% moisture content, both can be set to individual species or other building materials, and both ship with a hard case and a calibration verification device. We ran both through the same lab tests, and the results are close enough that the decision comes down to one feature rather than to accuracy.
The short version: the D300 scored 82% overall and the DS500 scored 81%. Choose the DS500 only if you need to read at two depths.
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| Bessemeter D300 | Bessemeter DS500, with the ¼ inch and ¾ inch depth markings |
Side-by-Side Test Scores
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Here is how each individual test scored, out of 5.0:
| Test | D300 | DS500 |
|---|---|---|
| Accuracy | 4.2 | 4.2 |
| Surface moisture | 1.0 | 1.0 |
| Meter temperature | 5.0 | 5.0 |
| Wood temperature | 5.0 | 4.5 |
| Reading repeatability | 5.0 | 5.0 |
| Drift | N/A (pinless) | N/A (pinless) |
| Cable interference | N/A (pinless) | N/A (pinless) |
What the DS500 Adds
The DS500 is a dual depth meter. It can be set to measure ¾ inch or ¼ inch into the material, which helps when you want to compare a surface layer against the core, or when you are working with thinner stock. You can see the two depth markings around the display in the photo above. The D300 reads at a single depth.
One caveat about the numbers: our DS500 review tested the ¾ inch setting. The ¼ inch mode was not scored separately, so every DS500 result here describes the meter reading at ¾ inch.
Where They Score Differently
Wood Temperature
Wood temperature is the only individual test where the two meters scored differently. The D300 scored 5.0 out of 5.0, reading about 1.5% high on higher moisture content wood at high wood temperatures. The DS500 scored 4.5 out of 5.0, reading about 2% low on higher moisture content wood at low wood temperatures.
The gap is small, but the direction of the error is worth knowing. In our wood temperature test, the D300 tended to read high on warm wood, while the DS500 tended to read low on cold wood.
Surface Moisture
Both meters scored 1.0 out of 5.0, and this is the most important thing to understand before buying either one. A small amount of moisture on the wood surface raised the D300 reading by 3.5% moisture content. On the DS500, surface moisture raised the reading by almost 5%.
If there is dew on the boards, or the stock has just come in out of the rain, neither meter will give you a number you can trust. Let the surface dry first. Our surface moisture test explains how we measure this.
What They Share
Both meters scored 4.2 out of 5.0 for accuracy. Each did well across all three species we measured in the lower moisture content range, and each tends to read somewhat high above 15% moisture content, particularly on hardwoods, when compared against ASTM D4442 oven-dry standards. You can see the method in our accuracy test procedures.
Both scored 5.0 out of 5.0 for reading repeatability, with very little variation across sequential readings, and 5.0 for meter temperature. Because both are pinless, the drift and cable interference tests do not apply to either one.
They also share the same two shortcomings: neither has a backlit display, and neither has a high moisture alarm.
Which One Should You Buy?
Buy the D300 unless you specifically need readings at two depths. Accuracy, repeatability, and meter temperature performance are the same on both meters, and the D300 finished one point ahead overall. The step up to the DS500 buys depth flexibility, not better readings.
For the complete results, see our Bessemeter D300 review and our Bessemeter DS500 review. Both meters also appear in our best wood moisture meters rankings.
How We Tested
Every meter we review goes through the same seven tests, run the same way on the same samples, so the scores can be compared directly across brands. Our review procedures describe each one.