Easily integrated pressure transmitters for OEMs
18 July 2011
Thanks to its Chip-in-Oil (CiO) technology, Keller's Series 4 LC-9 LC pressure transmitters incorporate a special ASIC for signal processing, fitted directly adjacent to the pressure sensor, in the same housing, under oil, and with the exclusion of air. This yields a host of advantages in terms of application; in particular, all the key pressure measurement components are now protected against the risks from humidity and condensation.
The interior wiring is implemented with short, lightweight bonding wires, while sintered-in pressure-resistant glass lead-through feed the transmitter signals out. Together with the high-grade stainless steel housing, they form a Faraday cage around the measuring system, acting as feed-through capacitors. This makes the CiO technology RFI resistant up to field strengths of 250V/m and for frequencies of up to 4GHz.
Series 4 LC-9 LC pressure transmitters offer two output signals: a ratiometricanalog voltage output and a digital inter-integrated circuit interface (I2C). The ratiometric signal eliminates the need for an expensive voltage reference in the support electronics to the A/D converter, with no additional effort and expense for compensation and calibration. For a supply of 5.0V, the output signal is specified as 0.5 - 4.5V. The transmitters provide constant protection against over-voltage and polarity reversal on all lines up to ±33Vdc.
Up to 128 OEM transmitters in Series 4 LC-9 LC can be addressed successively by one I2C master in order to call up the current pressure and temperature values from the transmitters (slaves). With an I2C output, the pressure transmitters can operate with a voltage supply of only 2.7-3.6Vdc, and they are ready to supply the current measured values 5ms after switching on. Appropriate on/off operation and low power consumption make these transmitters suitable for mobile applications.
With an analogue output, the transmitters can be used at temperatures of between -40°C and +150°C, and with an I2C output the range is from -40°C to +80°C. The full scale pressure ranges for the analogue version extend from 2bar to 1,000bar, and for the digital version from 2bar to 200bar. The internal sampling rate is 2kHz. The digital version draws less than 3mA, and the analogue version draws just 8mA, in operation.
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