TE - White Papers

WHITE PAPER PAGE 6 TE CONNECTIVITY SENSORS /// WHITE PAPER Analog and Digital Transducers — the Advantages of Both There are applications and markets for both analog and digital transducers, and each have specific advantages for a particular application. See our case study examples. A CASE FOR AN ANALOG SENSOR Some applications have unique conditions that must be considered when deciding on an analog versus a digital transducer. Monitoring the pressure of chemical processes in an oil refinery is a good example. Because of the way a refinery is designed, a pressure transducer is sometimes located hundreds of feet from the control system to which it's attached — requiring a long cable run to make connection. These cable runs make excellent antennas that pick up EMI/RFI/ESD signals from adjacent cabling and machinery. However, this electrical "noise" can overwhelm, distort, or corrupt high-impedance analog signals in the cable. A common technique to overcome this problem is to use a high current, low impedance transmission method that's immune to the noise sources. The 4-20 mA current loop was developed solely to provide this capability. At the transducer, the pressure signal is used to control the amount of current the sensor draws from the power supply located at the controller location. For a signal level of zero, the transducer draws 4 mA of current. For a maximum signal level, the transducer draws 20 mA. For any signal in between the limits, the current draw will be a value that is ratiometric to the signal level. Everything about this approach is analog. It's an excellent way to help eliminate problems caused by EMI/RFI/ESD. The M3200 pressure transducer is available in an analog 4-20 mA version with 12 different pressure ranges. A CASE FOR A DIGITAL SENSOR A new market is emerging for industrial pressure transducers that's referred to as the Industrial Internet of Things (IIoT or Industry 4.0 for short). The basic idea is to populate a factory with sensors and transducers that monitor every critical parameter of the manufacturing process. The collected data is sent to a central computer, or to the cloud, where analytics are applied, and the data is stored. All of this is done in the digital domain for efficiency of communication, analysis, and storage. It makes sense to use a transducer that provides data in a digital format. This reduces system costs and makes it more convenient to interface the transducer to the control electronics.

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