2017-05-12
User Manual
SONO-MIX MINI Version 2_7
Page 17
2.3.1. Shortest expecting mixing times and density effects at partial loads
Time to evaluate signal at dry mix stage
The sensor can be configured depending on the requirements of the applications, but in the pre-setting
it requires 15-20s till the value is stable after filling the mixer with aggregates and cement.
Time to evaluate signal at wet mix stage
The sensor will immediately detect the incoming water, but commonly it lasts a little till the water is
distributed homogeneous, thus we suggest not to have shorter wet mixing time than 45s.
Does density have an effect on accuracy
If the mixer load varies from 20% to 100% of total mixer capacity, it needs to calibrate for different
loads. At 20% load, the sensor could experience no material or less material
Different density does always have an effect and on any sensor, operating with an electrical field, but
how strong this effect is depends on the installation place in the mixer, as closer to the wall of the mixer,
as less this effect is, as due to the mixing energy with smaller batches more material is located at the
outside of the mixer. But it always has to be ensured, that at least one mixing tool cleans the sensor per
turn, to ensure the sensor stays clean! Even if close to the wall you will see at least a slight effect of the
filling amount.
2.3.2. SONO-MIX to control the water/cement ratio
SONO-MIX can be also used to control the w/c-ratio by determination of the moisture respectively the
water content at the end of the mixing process. Similar as described in the previous chapter, a recipe
specific calibration with the PLC in the mixing plant can be made at the end of the mixing process with
the final fresh concrete. Depending to the concrete recipe the probe has to be calibrated with two points
in the mixing plant, however this two points shall lie in a closer and higher moisture range, e.g. between
7% to 8% due to the concrete type. With the determined moisture or water content and the known
cement content, the w/c-ratio can be calculated. It should be considered, that the PLC should calculate
the moisture content with several single values over 3 to 5 seconds shortly before the discharge of the
mixture.
