Will temperature affect the accuracy of instrument readings?
The short answer is yes, but the degree is usually very small in needle instruments. As the temperature of the wood increases, its resistance decreases, leading to an increase in the indicated% MC of the sample. For on-site conditions, if the temperature of the tested wood sample is between 50 ° F (10 ° C) and 90 ° F (32.2 ° C), there is no need to correct the temperature reading results.
When measuring wooden materials that exceed these temperature values and the instrument itself does not have built-in temperature correction, you can use a temperature correction chart to find the correction (Delmhurst provides these corrections for each humidity meter).
The needle free measuring instrument does not measure resistance, so unless the sample is completely frozen, their readings are not affected by the temperature of the wood.
How to correct readings for different types of wood?
Using needle and needle free moisture meters, the type of wood will affect the readings you obtain. For needle instruments, the difference in readings is due to the inherent resistance characteristics of different types of wood. For needle less instruments, the specific gravity (SG) of wood can affect the reading results.
Each hygrometer is usually calibrated using a specific type of wood, such as Douglas fir or oak, which makes the instrument accurate when measuring that type of wood, but less accurate for other types of wood.
Usually, there are two methods to correct readings for a given type of wood:
1. Use the species correction table provided by the instrument manufacturer.
2. Use instruments with built-in species correction.
Using instruments with built-in calibration functions is usually easier and faster than referring to manuals and performing mathematical calculations on your own.
How to determine the distribution of moisture in a circuit board?
To determine the distribution of moisture in the circuit board, you need to use a pin type meter with insulated pins (non insulated pins can be used, but insulated pins can make this easier).
Firstly, remove the pins of the instrument and gently push them into the material to be tested. Read the "shell" or outer layer of the board. After reading, push the pin in increments of 1/16 inch and take out a new reading at any time. By recording humidity readings of circuit boards at different depths, you can effectively indicate the distribution of moisture in the circuit board.
Why not use a needle less meter? Because a needle less instrument can read the humidity of the entire area and the depth of a single digital scan, it cannot separate the depth of moisture presence.
