Tsunami Sensor off Kushiro - Tokachi Two seabed tsunami sensors are installed in the Kushiro-Tokachi System. * By clicking the image to the right you can display an expanded version of a photograph of the exterior of the seabed tsunami sensor.

1.1 Outline
The tsunami sensor consists of two oscillation circuits, with oscillator elements of (1) pressure-detection crystal resonator that, with stability and over the long term, detects minute changes in pressure and (2) pressure-reference crystal resonator that has the primary objective of compensating for temperature changes.  The difference in frequency of each crystal oscillator is outputted as a tsunami signal (7 kHz to 16 kHz). The thermometer consists of a temperature-measurement crystal resonator and a temperature measurement oscillator.  The thermometer outputs, as a frequency signal (3.776 MHz at 2 °C), the temperature measured by the temperature-measurement crystal resonator.  The temperature-measurement crystal resonator is affixed to the interior of one end of a pressure container.  The temperature-measurement oscillator is mounted inside the transmission unit.
1.2 Specifications
1.2.1 Tsunami Sensor  1) Detection system  2) Output frequency  3) Characteristics of power variation  4) Characteristics of temperature variation  5)  Linearity	Crystal oscillation system 7 to 16 kHz Respective of current variation of DC 14 mA ± 10 %, output frequency varies within ± 10×10 ppm. Frequency change in line with surrounding temperature variation of 2 to 16 °C is within 500 ± 10 ppm / °C. Linearity of water pressure frequency variation characteristic of a max. of 400 kg/cm² is within ± 10 %.
1.2.2 Thermometer  1) Detection system  2) Output frequency  3) Sensor measurement scope  4) Frequency temperature characteristic	Crystal oscillation system 3.776 MHz ± 50 ppm (at 2 °C) 0 to 15 °C approx. 12 ppm / °C
1.3 Data Processing
1.3.1 Pressure Data Transmission from the seabed is done by making the pressure frequency (variation of approx. 12 to 13 kHz in a state of installation) into a gate. Transmission then is performed with timing of 8 kHz (256 division of 2.048 MHz) for the count value of the pulse of the system-standard-clock (2.048 MHz).  In the relation of 8 kHz versus 12 kHz, the gate may rotate several times, therefore the summation of the number of rotations and the count value is transmitted to land. On land, every 8 kHz of data is estimated 800 times, each with a 0.1 second value.
1.3.2 Temperature Data Regarding the temperature data, the gate circuit has timing of 8 kHz.  The pulse of the temperature crystal frequency is counted, and the count value thereof is deemed as data.