TDC- Ultrasonic Thickness Meter

The velocity of sound in aluminum is 5100 m/s (at 20 °C). An ultrasonic pulse is reflected on both, the entry wall and the back wall. Take as an example a layer of 1 mm aluminum . The difference in travel time for the two reflected pulses is 2*d/c = 3,9 µs. For a needed resolution of 0.1% this means a resolution of time of 390 ps - no problem for the TDC! A TDC can measure even a layer of 10 cm aluminum with the same absolute resolution!

TDC ADVANTAGES

• Small size: Single-chip solution in the small QFN/TQFP-package
• You need a broad dynamic range? That's no challenge for our TDC. The TDC-GP1 e.g. allows measurements up to 100 ms with the high resolution of 110 ps - this equals a dynamic range of 30Bit!!
• Highest resolution: by averaging - the TDC is well suited for this - the standard deviation can be reduced down to several picoseconds
• Industrial operating range: from -40 °C to 120 °C
• Battery applications: for handheld devices low current consumption is essential. Discover the TDC - it is perfect for this! When you work in measuring range 2 with only one measurement plus calibration per second, the current consumption will be only 3 uA for a 5V supply (Remarkable: nearly the complete 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
• Temperature measurement: The velocity of sound depends on the temperature. Therefore it's essential to permanently check the temperature of the fluid. As a temperature measurement can be reduced easily to a time measurement, we have already implemented the necessary functions into the TDC. The temperature-unit allows a resolution of 0.002 °C