The ’heart’ of Mininfra grain analysers is a unique, patented optical arrangement called ‘SBCS’ – Single Beam Compensation System.
Complex mechanical elements
Due to the samples’ granularity and inhomogeneity related to the size of the light beam one measurement does not give a satisfactory result: to get an acceptable accuracy and repeatability we have to average the results of hundreds of elementary measurements. ‘Traditional’ instruments divide the sample into sub-samples and measure these sub-samples or move the sample and measure it on more spots to reach a representative sampling. These methods require usually complex and expensive mechanical solutions.
In case of quantitative analyses, where not only the type of components but also their percentages have to be determined, very stable and accurate analyses are required. Stability can be achieved only if we compensate the changes of the measurement system (e.g. warming up, changes of parts, etc.) with simultaneous measurement of a very stable optical element (optical standard). ‘Traditional’ instruments do this usually by implementing 2 measurement ‘channels’ or doing 2 consecutive measurements:
– the 1st solution is expensive any only acceptable if the 2 channels are absolutely equal,
– the 2nd solution can’t be a perfect solution theoretically because of the time elapsed between the 2 measurements.
High demand on light intensity
NIT instruments measure the sample and the high stability optical transmission standard at the same time. The instruments calculate the logarithm of the ratio of the light intensities measured on the sample and the optical standard. From these data the percentages of the components are calculated by averaging, based on the stored calibration equations. In order to be able to measure the sample and the high stability optical transmission standard at the same time, ‘traditional’ instruments divide the light of the lamp into 2 beams: one beam trans-illuminates the standard, the other beam trans-illuminates the sample. This light intensity can be produced by a high power lamp associated with significant heat generation which warms up both the instrument and the sample.
Our patented optical arrangement SBCS is different from all of the above because it applies only one optical channel and the elements of this channel are rotating. This means that by SBCS representative sampling can be achieved by moving the light and not by moving the sample: a high speed rotating light beam scans the sample on a large surface.
The light beam measures the sample at 16 different sequential spots and in each cycle it measures the transmission optical standard too. The speed of the rotation ensures the simultaneity of the representative measurement of the sample and that of the transmission standard.
This simultaneity and the optical arrangement applying only one optical channel result in perfect compensation.
Advantages of SBCS
-simple machinery with very few moving parts;
-small size, light weight;
-uncomplicated and cheaper production and service;
-low power lamp, less heat generation, but still high light intensity;
-unaffected by temperature, no warm up time: the instrument can be used right after turning on;
-the lamp is only lighting during the measurement which provides much longer lifetime and no regular change is needed.