Pressure Sensor Readings (Pressure Transducer, Pressure Transmitter)

Pressure sensors, also known as a pressure transducers or pressure transmitters, take an applied force and convert it into a proportional electrical signal which is then output to a PLC or other controlling device. The controlling device then converts the signal to a pressure reading on a range scale, proportionate to the signal level, in a usable form such as P.S.I., bars, etc.

When selecting a pressure sensor, it is important to select one with an output that other parts of your system can read. There are four main types of pressure sensors outputs.

Millivolt: Produces a millivolt output which is driven by the excitation level of the input. For example if your output is 2mV/V, and your input is 10V then the full scale output would be 20mV, if your input was 5V then the full scale output would only be 10mV. Because the level changes with the input, typically a voltage regulating power supply is used to maintain a stable excitation level. These types of pressure sensors are the most widely used due to their low cost, however they are only able to transmit the signal a short distance and are susceptible to electrical interference from nearby devices. If the voltage level of the signal needs to be higher, either to be read by the system or to travel further distances a signal amplifier should be used at the output of the device.

Voltage: Outputs a voltage signal in a range readable by most systems, usually 0-5V or 0-10V. Typically this is not dependent on excitation level so they work well with unregulated power supplies. They are less susceptible to electrical interference and can transmit the output signal longer distances, because of this they are usually used in industrial environments where a millivolt sensor isn’t feasible due to electrical interference or harsh conditions.

4-20 mA: These pressure sensors output a signal between 4mA and 20mA. They are the least susceptible to electrical interference from nearby devices and can transmit a reliable signal over distances of 1000ft or more.

Digital: Digital pressure sensors output a digital signal. They are more versatile than the analog sensors and capable of communicating other factors as well as pressure readings, such as transmitting location, recording logs, alarm signals, etc. They produce little electrical noise and have the longest transmission distances. Typically used when smart sensing and additional functionality are necessary. It is important when selecting a digital pressure sensor to choose one that uses a communication protocol that is compatible with your system, I2C, SPI, UART, etc.