Table 4.

Estimated parameters and evaluation criteria for the linear and several polynomial equations for THT-B121 resistive sensor using 11 salt solutions.

	Linear	2nd Order	3nd Order	4th Order
b0	0.028672	−2.74999	−11.0702	−20.5303
b1	1.008985	1.13766	1.780025	2.805196
b2		−0.0011437	−0.01432	−0.0491534
b3			7.81681 × 10−5	5.39281 × 10−4
b4				−2.07539 × 10−6
R 2	0.9967	0.9974	0.9987	0.9993
s	1.6098	1.4612	0.982	0.7719
Residual plots	clear pattern	clear pattern	clear pattern	uniform distribution