The tank shown in the illustration is an indoor tank for hot food scraps, which, in addition to its rugged design, is paired with an automatic emptying management system. The essence of the system briefly: the daily food residue is emptied into the tank with a vacuum pump system. The consistency and amount of stored medium are entirely variable. The change in level in the tank is also completely unpredictable, so measurement is required that has long-term stability and tolerance to temperature changes and that the contents of the tank are not intermittently inverted to avoid permanent settling, so the surface of the medium may be conical, may become swirling. The MicroTREK guided microwave transmitter family was chosen because of these challenges.
The outlet of the automated system is a GSM telemetry module that sends an SMS notification to the sewage company when the tank reaches 80% of its storage capacity, which can be connected to the drain on the outside of the building and emptied.
During the Covid-19 quarantine period, kitchen utilization dropped significantly, so the amount of food left in storage per day also fell sharply, making it very important for the transmitter to measure near-stagnant levels with sufficient stability.
A further challenge is the presence of certain sticky components due to the composition of the medium, which carries the risk of causing a measurable reflection when larger deposits are formed around the transmitter probe, which can lead to false level measurements.
The MicroTREK HT–400 series has reached the tolerance limits earlier in this application, as the signal processing threshold level can only be set under strict rules. There has been a situation where a mass above the average and adhering to a probe close to the upper limit has produced a false level value that has incorrectly sent an emptying request to the recently emptied tank.
Leveling with the new MicroTREK HT–700 electronics has helped eliminate such leveling anomalies.
The firmware of the new electronics allows us to set more flexible threshold handling depending on the position of the reflection, and we can also freely parameterize the slope of the threshold curve. With such options, you can easily fine-tune the measuring device to the specifics of the measurement task.
Experience to date confirms the reliability of the new measurement evaluation process.
The above test operation is rightly considered a milestone in the history of the development of guided radar level transmitters, as we have not always been able to eliminate the occurrence of erroneous level measurements with software settings in the case of materials adhering to larger probes.
However, it is worth keeping in mind that in a challenging application such as the one above, the versatility of the revamped MicroTREK device is a great advantage, but the expanded software toolbox usually requires a more thorough analysis of the application’s features.
