I�C was designed to communicate over short distances between printed circuit boards and is really a simple, 8-bit serial data bus. In the meantime, it isn’t only PCB-mountable pressure sensors that utilize the I�C signal for data transfer, but additionally pressure sensors remote from customer electronics.
Remote sensors usually have the advantage of being less sensitive to contaminated or aggressive media and having the capacity to measure directly at the process. In the case of sensors mounted on the circuit board, the sensor element is, in many cases, exposed directly to the medium. With remote sensors, steel or ceramic generally serve as the wetted surface.
I�C circuit
The I�C bus, alongside the two supply lines, requires only two further lines:
SCL (serial clock line)
SDA (serial data line)
Additional possibilities through I�C
The I�C bus is a well-known standard in electronics, offering additional possibilities for communication with a pressure sensor than with an analogue signal:
In the data protocol, in addition to the pressure value, a temperature value and diagnostic information (for example an integrity test of the info transfer) can be transmitted via a status byte.
Several pressure sensors could be connected to a bus line as ?slaves? to the customer electronics that functions as a ?master?.
On the customer side, as opposed to the usage of pressure sensors with analogue signals, the analogue-to-digital conversion of the pressure value for further signal processing is unnecessary because the pressure value is already within digital form. This contributes to faster and easier signal processing.
The electronics for communication could be built with standard components readily available on the market.
Often, I�C signal pressure sensors are also optimised to take less energy, making them perfect for battery-powered applications. In the WIKA portfolio, for example, this applies to the MPR-1 pressure sensor module.
Boundary conditions by using I�C
Since I�C isn’t a fieldbus, long wire lengths are not recommended. The maximum wire length depends, at length, on the operating environment and the corresponding disturbing influences. I�C communication is best used in projects where the pressure sensor or the pressure sensor module is built-into the customer product and thus protected against external influences. It should also be noted that with any digitally processed signal, the response time due to discrete-time sampling will be somewhat slower than for an analogue, continuous signal.
Note
Your contact person will undoubtedly be happy to assist you to with any more questions on digital interfaces.
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