Hydromette Compact B evo-100 capacitive structural moisture meter

All three cases determine the moisture of set building materials and other materials directly on site using the calcium carbide method; the measuring range is the same: 0.30 to 7.5 CM-% via the gauge readout and 0.14 to 22.9 CM-% via the conversion table. Common items include a pressure cylinder with lid and Premium gauge, electronic scales and the carrying case P.

• CM-B Standard: basic equipment without digital timer, with 2 vials of test water.
• CM-B Pro: additionally a digital timer for recording the time during the measurement.
• CM-P Pro: additionally a digital timer, a manual pestle for crushing the sample directly in the pressure cylinder, 5 instead of 2 vials of test water and the Hydromette Compact B evo-100 for non-destructive pre-testing of larger areas.

A dash means that the meter does not support this measurement: the HB 30 and BL E 2 do not measure air humidity, and the UNI 1 and UNI 2 do not measure wood moisture. The UNI 1 and UNI 2 are intended as a complement to a wood moisture meter. The B 55 BL, OT 100 BL, ET 10 BL and TT 40 BL are connected to the BL E 2 via the AK 2 adapter cable.

• Drive the electrode pins in across the grain; GANN wood moisture meters are based on this measuring direction. Parallel to the grain the meter shows readings that are too high, by approx. 2 percentage points at around 20 % wood moisture.
• For the average moisture content, measure at a depth of 1/4 to 1/3 of the wood thickness; the 16 mm and 23 mm pins supplied with the M 20 are intended for wood thicknesses of 30 to 40 mm and 50 to 65 mm respectively.
• Set wood species group 2 or 3 according to the enclosed wood species table.
• The readout applies to a wood temperature of 20 °C: colder wood gives readings that are too low and warmer wood readings that are too high; these are corrected with the correction table in the operating manual.
• Above the fibre saturation point, from approx. 30 % wood moisture, accuracy decreases.

Cement screed is darker and coarser, whereas calcium sulphate screed is lighter and finer.

An exact measurement is difficult in multi-layer constructions because the materials used have different bulk densities. Comparative measurements are, however, possible.

Salts normally contained in masonry change the readings only slightly. Visible salt deposits on the surface, however, increase the readings; they should be brushed off as far as possible before measuring.

The CM method is a mechanical-chemical process whose accuracy depends above all on correct sampling across the entire cross-section, low moisture loss during sample preparation and a tight pressure system.

• Test water (vials of 0.7 ml each) is used to check the tightness of the pressure cylinder and the operability of the gauge.
• The manual pestle crushes the sample directly in the pressure cylinder; this preserves the sample moisture. It is included in the CM-P Pro and also fits the CM-B Pro.
• The units work with a small sample quantity, e.g. 20 or 50 g; the case includes electronic scales up to 500 g with 0.1 g resolution.
• Remove the sticker from each calcium carbide ampoule before measuring; a sticker that has not been removed can influence the measurement result.

The electrodes are connected to the UNI 2, HB 30 or BL E 2 via the MK 8 measuring cable.

Without pre-drilling and contact paste the meter may show considerably too low values in hard building materials. Insulating materials should not be pierced completely, as the underlying building material, which is usually already damp, can otherwise produce a wrong value.

For dry mineral wool or glass wool, readings of 5 to 10 digits are normal.

Both are capacitive structural moisture indicators with a ball probe that measure non-destructively using the dielectric constant/radio frequency principle and run on a 9 V block battery. The differences:

• BL Compact B 2: scan mode 0 to 200 digits (resolution 0.1 digits); characteristic curves for 7 building materials with direct readout in wt.-% or CM-%; one limit value per material with acoustic signal; internal memory for max and hold function; three-line LCD; mini USB for firmware updates via GANN Dialog Pro.
• Compact B evo-100: scan mode 0 to 100 digits (resolution 1 digit, tolerance ±5 digits); self-luminous OLED display with hold function; for gypsum- or anhydrite-bound and cement-bound building materials, the manual contains a comparison chart to wt.-% or CM-%. The meter is also part of the Hydromat CM-P Pro measuring case.

Digit values from meters with 0 to 100 and with 0 to 200 digits are not comparable; because of the different measuring depths, no conversion factor should be used either.

A generally applicable limit value for readiness for covering cannot be laid down: the assessment depends, among other things, on the building material, the long-term ambient climate and the planned covering, and requires technical and expert experience.

In cases of doubt, contact the manufacturer of the floor covering or coating and take the recommendations of trade associations and guilds into account. For the on-site decision on readiness for covering, the CM measurement with the Hydromat measuring cases is suitable; capacitive readings, for example from the BL Compact B 2 or Compact B evo-100, should be verified by a CM or resistance measurement.

• Structural moisture test adapter: connect it via the MK 8 measuring cable and set the selector switch of the UNI 2 or HB 30 to position B. The meter should display 45 digits with a tolerance of ±2 digits.
• Temperature test adapter: connect it to the 7-pin socket instead of a temperature probe and set the selector switch of the UNI 1 or UNI 2 to 200°. Target reading: 0 °C with a tolerance of ±0.5 °C.
• BL E 2: select the material setting according to the label or the instructions of the test adapter; no active sensor may be connected. If the pins of the M 6 or M 20 are held against the adapter sockets, the electrode is checked as well.

If the structural moisture reading deviates, the check should be repeated with a new MK 8, as a defective cable is usually the cause. All measuring equipment should also be checked by the manufacturer every 2 to 3 years, depending on the frequency of use.

• Resistance-based (UNI 2, HB 30 or BL E 2 with electrodes such as M 6, M 20, M 21 or M 25): the resistance between two electrodes inserted into the material is measured. The method is common; it allows moisture profiles and depth measurements.
• Capacitive (BL Compact B 2, Compact B evo-100 and the active electrodes B 50, LB 71 and B 55 BL): non-destructive, without drilling or driving in; suitable for a qualitative assessment, for detecting the moisture distribution and for pre-testing. Capacitive meters are moisture indicators; for expert reports their results should be verified by a resistance or CM measurement.
• CM measurement (Hydromat CM-B Standard, CM-B Pro and CM-P Pro): the calcium carbide method, widely used and particularly for screeds.

Digit values from resistance-based and capacitive measurements are not comparable with each other.

• Hold the meter or electrode only by the rear half or the lower part of the housing; the half with the ball and display must remain free, otherwise the hand influences the measuring field.
• Place the ball firmly and as perpendicular as possible (approx. 90°) on the building material.
• Keep a distance of approx. 8 to 10 cm from corners, angles and edges; measurements in drilled holes or chiselled recesses are incorrect measurements.
• Metal in the substrate such as reinforcement, cables, pipes or plaster rails can increase the reading depending on the cover depth.
• For classification, first measure up to 5 points within an imaginary square of approx. 20 cm at a spot known to be dry and use the mean value as a reference; only compare identical materials or structures.