A pressure transducer, commonly known as a pressure transmitter, is a transducer used for converting the pressure into an analog electrical signal. There are many pressure transducer types, one of the widely used is the strain-gage base transducer.
Pressure transducer has a diaphragm, to which strain gages are bonded and wired into a wheatstone bridge configuration. The physical deformation of strain gages results in conversion of pressure into an electrical signal. As the pressure is applied to the pressure transducer, it generates a deflection of the diaphragm that causes strain to the gages. This strain produces an electrical resistance change proportional to the pressure.
The Electrical Output of Pressure Transducers
Pressure transducers are accessible with three types of electrical output; millivolt, amplified voltage and 4-20mA.
Summary of the outputs and their best usage
Millivolt Output Pressure Transducers
As the name implies, the pressure transducer has millivolt output and is the most economical transducer. 30mV is the normal output of the millivolt transducer. The input power or excitation of the pressure transducer is directly proportional to the actual output. As the excitation fluctuates, the output changes. As there is a dependence on the excitation level, millivolt transducers are supplied with regulated power supply suggestions. This transducer must not be located in an electrically noisy environment as the output signal is so low. There must also be shorter distances between the transducer and the readout instrument.
Voltage Output Pressure Transducers
Voltage output transducers in comparison to millivolt transducer provide higher output owing to its integral signal conditioning. 0-5Vdc or 0-10Vdc is the normal output. Unlike millivolt pressure transducer, the transducer output is not a direct function of excitation. If the power supplies are unregulated and still they fall within a specified power range, it is sufficient. These transducers with higher level output can be used in industrial environments as these are unaffected by the electrical noise.
4-20 mA Output Pressure Transducers
The transducers that fall in this category are also called pressure transmitters. These are ideal for transmitting signal to long distances, as a 4-20mA signal is least affected by electrical noise and resistance in the signal wires. Rarely this transducer is used in applications where the lead wire must be 1000 feet or more.