Different Types of Pressure Transducers

Many capillary transducers are filled with mercury. Since the diaphragm of the transducer is quite thin, there is a danger of the diaphragm rupturing and leaking mercury into the plastic and into the workplace. Unfortunately, many transducers do not carry a label indicating that the transducer is filled with mercury, so adequate safety precautions are not always taken. It is important to make sure that mercury-filled transducers are not used in the extrusion of medical products and food packaging products. In these situations, other liquids can he used inside the transducer the most common alternative to mercury is NaK (sodium-potassium). 

Another type of transducer is the pneumatic pressure transducer. It has good robustness, but poor temperature sensitivity, poor dynamic response, and average measurement error. The capillary transducer has fair robustness, fair temperature sensitivity, and fair dynamic response. The total measurement error varies from 0.5 to 3% depending on the quality of the transducer. The pushrod is similar to the capillary transducer, except that it tends to have poor temperature sensitivity and poor total error. The piezo-resistive transducer has good robustness because of its relatively thick diaphragm, good temperature sensitivity, good dynamic response, and low measurement error. A comparison of different pressure transducers is shown in Table 4.1. 

Transducer type Robustness Temperature sensitivity Dynamic response Total error 

Capillary strain gauge Fair Fair Fair 0.5 to 3% 

Pushrod strain gauge Fair Poor Fair About 3% 

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