Check Your Moisture Meter's Calibration in 3 Easy Steps

Posted by Tom Laurenzi on Oct 28, 2016 9:30:18 AM

One of the biggest concerns when taking moisture readings is making sure the meter is in calibration so that you get accurate readings . When a meter is not calibrated, you may get faulty results—and being just one or two percentage points off can have a significant impact.

So, being able to check a meter’s calibration is crucial for ensuring accuracy.

Because not all moisture meters are the same, it’s important to know about the different types of calibration check methods that are available.

Some meters have built-in calibration tests that let you check accuracy literally with the push of a button. However, checking your moisture meter’s calibration may not be that easy—or you may just want to check your results with a different test method.

In either case, here are a few quick steps for checking your moisture meter’s calibration:

Using a Moisture Content Standard (Pin Meters)

  1. MCS-JL-2000.jpgPlace the meter’s pins on the moisture content standard’s (MCS) metal contacts
  2. Turn on the meter.
  3. Check the reading & compare to value given in instructions (different standards may be calibrated for different values).

If the reading is different from the one the MCS was set for, then the meter is out of calibration. Try inserting a replacement battery and repeating the test. If results are still off, you may need to send the moisture meter back to the manufacturer.

Using a Sensor Block (Pinless Meters)

  1. Hold the meter to the sensor block—make sure the scanning plate is making solid contact with the block.
  2. Turn on the meter.
  3. Check the reading and compare to the sensor block’s instructions.

Like with MCS checks for pin meters, if the reading is different than what the sensor block is supposed to read, then the meter may need to be recalibrated by the manufacturer.

Using a Reference Meter (Both Pin and Pinless Meters)

Using a reference meter to check calibration is less accurate than checking with an MCS or sensor block, but it can be a good solution if your meter doesn’t have a built-in calibration check feature, or if you don’t have a moisture content standard. This method requires you to have a second, IDENTICAL moisture meter to use as a reference—which is more expensive and inefficient than using built-in checks or purpose-built testing tools.

This reference meter should only be used for reference checks, and then tested using a different method every few uses. I personally recommend using built-in checks or a moisture content standard over using the reference meter method.

Pin Meter Reference Checks:

  1. Push the pins of the meter being tested to their full depth.
  2. Activate the meter and record the reading.
  3. Take the reference meter and insert the pins into the material, using new holes as close to the first set of holes as possible.
  4. Activate the reference meter and compare to the first reading.
  5. Repeat the process at a different testing site, using the reference meter first.

If both meter readings agree both times, this is a good indication that the meter you’re testing is in calibration. If the meter is consistently lower or higher than the reference meter’s readings by a fixed amount, then you know one of the meters is off.

Pinless Meter Reference Checks

  1. Press the test meter’s scanning plate firmly against the wood.
  2. Activate the meter and record the results.
  3. Press the reference meter’s scanning plate to the same area as the first.
  4. Activate the meter and record the results.
  5. Repeat steps 1-4 once or twice.

If the results agree or are very close (+ or - less than 0.1%), then the meters are most likely in calibration.

If results differ, then either one meter is inaccurate. Marking out a test site is strongly recommended to ensure consistent placement between the two meters.

The Best Testing Method

When you want to check moisture meter calibration, I would strongly recommend using either a built-in check, or a specialized testing tool such as an MCS or sensor block. These testing methods are much more reliable than reference checks—not to mention faster and easier.

Even using both built-in checks and an MCS or sensor block takes less time and effort to do than using a reference meter. Don’t get me wrong I would love for you to buy a second moisture meter for doing tests—I just know that using an MCS is the better option for most.

Learn how you can get a moisture content standard or sensor block for your Delmhorst moisture meters today!

The Craftsman's Guide to Using Woodworking Moisture Meters