ISO 15212-2:2002 pdf download
ISO 15212-2:2002 pdf download.Oscillation-type density meters -Part 2:
Process instruments for homogeneous liquids.
ULWFi tIi tWO UF1SIL iiieaureiiierit FldII U -t- IU Li duO — IU Li 110111 tillS iiieaui uuledsUrluly teuuiperature.
6.2.2 Effect of liquid properties
6.2.2.1 The density measuring transducer shall be constructed in such a way, that the maximum permissible errors are in accordance with the requirements given in 9.1 when measuring liquids with different sound velocities and, where appropriate, having different viscosities.
6.2.2.2 For testing, use Newtonian liquids with known densities and sound velocities as well as, where appropriate, known viscosities. They shall cover the intended application range of the density meter specified by the manufacturer with regard to sound velocity and viscosity. Testing shall be performed in accordance with 9.2.
6.2.3 Deviation between liquid and sensor temperatures
6.2.3.1 The density measuring transducer shall be designed to minimize the deviation between liquid temperature and sensor temperature. The density deviations due to this temperature deviation at constant flow and temperature shall not exceed 50 % of the specified maximum permissible error of the density measuring transducer.
6.2.3.2 Testing shall be performed by comparing the densities determined by the density measuring transducer with the actual densities of a suitable test liquid of known density at three different temperatures, being approximately the lower, upper and mean value of the specified liquid temperature range. Ambient temperature shall be kept constant to within ± 1 °C of the mean value for the specified ambient temperature range of the density measuring transducer. For this test
— switch on the density measuring transducer and circulate the test liquid for at least 1 h at a temperature as specified above and at a suitable flow rate;
— determine the actual liquid temperature as mean value of the temperatures at the inlet and outlet of the density transducer, measured by suitable thermometers;
— calculate the deviation between the actual density of the test liquid of known density at the actual liquid temperature and the density displayed by the density measuring transducer;
— repeat the test at the two other temperatures specified above.
Ethanol, n-nonane or mineral oil are suitable test liquids for this test.
6.2.4 Effect of instrument parts oscillations
6.2.4.1 Measurement deviations arising from parasitic resonances of instrument parts on the density measuring transducer shall not exceed 35 % of the maximum permissible error over the whole measuring range, specified for the density measuring transducer by the manufacturer.
6.2.4.2 For testing, examine the oscillatory characteristics of the built-in density sensor provided by the manufacturer. This test may not show any parasitic resonant points (see 3.3 of ISO 15212-1:1998) whose effects exceed 35 % of the maximum permissible error specified for the density measuring transducer by the manufacturer over the whole density measurement range.
6.2.5 Effect of instrument positioning
6.2.5.1 Unless otherwise specified by the manufacturer, the maximum permissible errors, in accordance with Table 2 or in accordance with the manufacturer’s specifications (see 9.1), shall not be exceeded if the position of the instrument is turned 90° from the vertical and horizontal sample flow direction.
6.2.5.2 Testing shall be performed in all three positions in accordance with 9.2 at constant temperature, pressure and density.
6.3 Liquid temperature measurement
6.3.1 Built-in temperature sensor
6.3.1.1 If the process density meter is equipped with a built-in liquid temperature measurement, the temperature sensor shall be fitted in such a way, that a good thermal contact with the liquid is guaranteed. The deviation between the displayed and actual liquid temperatures shall not be greater than the maximum permissible error of the density measuring transducer multiplied by the factor 0,2 °C x kg1 x m.
NOTE This factor has been defined by assuming an extreme thermal density deviation of 2,4 kg x m 3K1.
If the application range of the density measuring transducer is limited to aqueous liquids and water-containing mixtures, the factor to be multiplied by the maximum permissible error can be increased to 0,5 °C x kg1 x m.
6.3.1.2 Testing shall be performed by comparing the temperature determined by the built-in temperature sensor with the actual liquid temperature at three different temperatures, i.e. approximately the lower, upper and mean value (preferably 20 °C) of the specified liquid temperature range. Ambient temperature shall be kept constant to within ± 1 °C of the mean value for the specified ambient temperature range of the density measuring transducer. For this test
— switch on the density measuring transducer and circulate water, or, if water is not suitable, a typical test liquid, for at least 1 h at a temperature as specified above and at a suitable flow rate;
— determine the actual liquid temperature as the mean value of the temperatures at the inlet and outlet of the density measuring transducer, measured by suitable thermometers.
