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Item #: GMH 38
Our Price: $495.00
Brush Electrodes  
GMS300/91 Needle probes  
GOK91 Surface Electrodes  
Electrode Handle  
GSP91 Surface Electrode  
Moisture Tongs  

Description  more details

Portable moisture meter for wood, construction and various other hard and soft materials including textiles, paper, wool, polystyrene...

  • Professional Moisture Meter
  • Library of 494 materials
  • 466 wood types
  • 28 construction materials
  • 0-100% u material moisture
  • Serial interface or analog output
  • Calibration protocol
  • Data logging option
  • Capacitive measuring method
  • Temperature compensated

The GMH 3800 series meter and accessories offer a comprehensive range of tools for measuring the moisture in wood, construction materials, textiles, papers, agricultural products and more. The accessories make the unit adaptable to bulk materials, thin materials hard and soft materials. The absolute moisture of 494 material types is displayed directly and can be automatically converted to water content. Calculation tables are not required and you get a moisture rating (wet ... dry) of the measured material. The 3851 unit includes data logging and the possibility of downloading data to a PC

Measuring method
The electrical resistance depends on the amount of moisture in the material. The device measures the values of resistance and converts them to the moisture value by means of integrated characteristic curves. The temperature effects the measurement and has to be compensated for, especially in the measurement of wood. This is done automatically when using the external thermocouple probe. Contact with the bulk material is achieved by means of electrodes or injection probes that are driven into the material (wood) or placed in bore holes (concrete) or are placed in close contact with a surface.
Interpretation depends on knowledge of the moisture content "u" or wet-basis moisture content "w". Woodworkers commonly use the moisture content u (sometimes referred to as MC). When evaluating firewood, wood chips etc., the wet basis moisture content w is needed. The instrument can be configured to both of the values. Please refer to chapter “configuration“in the manual.
Moisture content u or MC (relative to dry weight) = dry basis moisture content. The unit is %, sometimes expresse as % MC.
The unit expresses the moisture content as calculated below:
Moisture content u [%] = (weightwet-weightdry) / weightdry*100
Moisture content u [%] = (weightwater) / (weightdry) *100
weightwet: weight of the wet material
weightwater: weight of water in the wet material
weightdry: oven-dryed weight of material.

Example: 1kg of wet wood, which contains 500g of water has a moisture content u of 100%

Wet-Basis moisture content w (relative to total weight, mind the arrow at left bottom!)
The wet-basis moisture content expresses the ratio of the mass of water to the total mass of the substance. The ratio is represented by the following equation (the unit is also %l)
wet-basis moisture w[%] = (weightwet-weightdry) / weightwet*100
wet-basis moisture w[%] = (weightwater) / weightwet*100
Example: 1kg of wet wood, which contains 500g of water has a moisture content u of 50%


Measuring Principle Resistive material moisture measurement acc. to DIN EN 13183-2:2002
Temperature External thermocouple, NiCr-Ni (type K)
Internal NTC
Measuring Range
Moisture 0.0 ... 100 % u (material moisture)
0.0 ... 50 % w (water content, wet basis)
(depends on selected characteristic
Temperature -40.0 ... +200.0 °C (-40.0 ... +392.0 °F)
Moisture rating 9 steps dry to wet
Resolution 0.1 % or 0.1 °C (0.1 °F)

Sensor - BNC with connection cable BNC to twin banana plugs
Temperature - Mini Thermocouple socket for K type sensor
Output mini jack socket for analog output or connection to digital converter

Device Accuracy  
Wood ±0.2 % material moisture (deviation from corresponding characteristic curve in range 6 ... 30 %
Building Material 0.2 % material moisture (deviation from corresponding characteristic curve)
Temperature (external) ± 0.2 % of m.v. ± 0.3 °C
Display two 4-digit LCD displays (12.4 mm and 7 mm high), additional indicator arrows
Output 3-pole jack connector Ø 3.5 mm, either with serial interface or analog output
Serial Interface connectable to RS232 or USB interface of PCs via electrically isolated interface converter GRS 3100, GRS 3105 or USB 3100 N (accessories).
Analog Output 0-1V freely scalable
Averaging 3 measurements
Power supply 9 V battery, additional socket for external 10.5 ... 12 V direct current power supply
Battery life ~120 hr
Working temperature -5 ... 50 °C (material not frozen )
Storage Temperature -20 ... +70 °C
Relative Humiduty 0 ... 80 % RH (non-condensing)
Housing impact resistant ABS housing
Dimensions approx. 142 x 71 x 26 mm (H x W x D)
Weight 155 g
Measuring Pins (nails) for use in wood Wood is measured with measuring-pins (nails ). Use electrodes: impact-electrode GSE91 or GSG91, or reciprocating piston electrode GHE91 to insert the pins. Punch in the pins across the wood-grain, having a good contact between the pins and the wood. Image to the left shows nail driving tool with electrical connections to the pins via banana sockets in the tool. The temperature probe is located close by. connection cable
GHE91 Impact electode with sliding hammer handle knocks nail into position and provides a means of connection via banana pin sockets in the tool
GSE 91 Nail insertion tool nail insertion toolAlternative pin nail insertion tool works by drilling a pilot hole in the wood then inserting the threaded spindle and screwing down so that the nails are forced into the wood. The electrical connection is made via banana sockets in the tool.

Measuring in Soft Materials
For Soft materials such as polystyrene use measuring pins as described for wood. The pins can be inserted without the use of the impact tools. Image at the left shows pins GST15B 3.8X15mm, GST25B 3.8x25mm and GST40B 3.8x40mm with connection hole for a banana plug

Measuring in hard materials - concrete and similar use brush type probes GBSL91 or GBSK9 which are inserted into predrilled holes. The image to the left shows the brush type electrodes connected to the input cable (BNC on the meter, banana plugs on the brush electodes. Available in two lengths 100mm and 300mm.wire brush electrodes

GMS 300/91 measuring needles for wood chips, wool, paper carton. use with GSG91 electrode handle.
GOK91 surface electrodes use with GSG 91 electrode handle.
GSG 91 Electrode handle for GOK91 and GMS300/91 with banana plug sockets
GEF38 Flat electrode pair for screed, paper etc., banana plug sockets.
GSP91 Surface electrode for textiles, paper and similar materials
GMZ38 moisture tongs for thin veneers or thin wood or similar up to ~10mm thick
GMK38 Connects from BNC on meter to banana sockets on probes

GTF38 thermcouple temperature probe for use with meter for automatic temperature compensation especially of wood.
2.2 fits in nail hole

Accessories kit for wood, building materials and similar.

Kit Includes
GKK 3500 (case)
GMK 38 (measuring cable)
GSE 91 (impact electrode)
GST 91 (measuring nails)
GTF 38 (temperature probe)
GMS 300/91 (measuring rods)
GBSK 91 (wire brush electrodes)
GLP 91 (conductive paste)
Includes space for meter


See other electrode accessories here (pdf)

Instruction Manual pdf

Order accessories a la carte here


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