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Ultrasonic Density meausrement

Process control is a very important part in chemistry and food industries. Especially the accurate measurement of the density of fluids challenges the engineers. With changes in conetration of the fluid the density varies and therefore the velocity of sound. A few steps to arrive at time measurement:

schematics The velocity of sound in water is 1483m/S (at 20°C). Many Solutions show a change of velocity of sound depending on concentration betwenn 1200m/s and 1800m/s. For a distance between ultrasonic tranceiver and receiver of 2cm this gives delays between 10us and 20us. With smalle distances of the transducers and an upper limit for velocity of sound of 10.000m/s we find delaytimes of only a few microseconds. The typical resolution of current available devices is about 0,1m/s -

This means a resolution in time of 500ps - for the TDC-GP1 no Problem!

And see all the advantages of the TDC in this application:

  • Small size: Single Chip-solution in the small TQFP44-package
  • Highest resolution: by averaging - the TDC-GP1 is well suited for this - the standard deviation can be reduced down to several picoseconds
  • Industrial operating range: from -45°C to 85°C even +100°C is possible.
  • Battery applications: for handheld devices a low current consumption is essential. Discover the TDC-GP1 - it's perfect for this! When you work in measuring range 2 with only one measurement plus calibration per second, the current consumption will be only 3uA for a 5V supply (Remarkable: nearly the comlete consumption is delivered to the calibration clock. If the active period of this clock can be fitted well, the current consumption can be reduced to nA!)
  • Supply voltage range: 2,7V ....5,5V
  • Temperaturemeasurement: The velocity of sound depends on the temperature. Therefore it's essential to permanently control the temperature of the fluid. As a temperature measurement can be reduced easily to a time measurement, we have allready implemented the necessary functions to the GP1. The RLC-unit allows a reolution of 1°C in the standard configuration. This value can be easily decreased by the use of some external components