How the DP-20 works

The DP-20 measures the oscillation frequency of an electronically excited U-shaped tube filled with the liquid medium. From the oscillation period at the characteristic frequency of the U-tube and two instrument constants the density of the medium is calculated with very high precision. A temperature sensor outside the U-tube is used to compensate for temperature effects on the oscillation. Finally, the salt concentration is deduced from the exact relationship between density and temperature dependent concentration. The monitored variables – density, salt concentration and medium temperature – are displayed on a switchboard mountable LCD display.

The DP-20 is pre-configured for solutions of NaCl, CaCl₂ and MgCl₂, which can either be selected over the Commander support software or remotely by three digital inputs. An additional custom solution can be configured by means of a density-concentration-temperature table.

With the mixing controller inside the M-version of the DP-20 salt solutions can be produced directly. The PD-controller automatically operates two switch outputs which drive the relays of the mixing valve and pump.