As stated in Table 5.4d, Ni-Span C seamless tubing, drawn to the profile in Figure 5.4c, is the best choice for Bourdon tube applications in all cases except those at very high pressure or those that are extremely corrosive. Direct indicators or motion balance transmitters using C-Bourdon elements are available with spans from 0–15 PSI to 0–20,000 PSI (0–100 kPa to 0–140 MPa) and can be used for positive, negative, or compound pressure ranges, but the indication on the vacuum side will not be accurate or sensitive. The accuracy
of these devices is a function of the Bourdon tube diameter, design quality, and calibration procedures. It can vary from ± 0.1 to ± 5% inaccuracy, with the majority of these units failing in the area of ± 1% (Table 5.11f).