INDIRECT METHOD TO ADJUST STRAIN GAUGES WITH BRIDGE MEASURING CIRCUIT BY MULTIPLICATIVE TEMPERATURE ERROR WITH ACCOUNT OF NON-LINEARITY OF TEMPERATURE CHARACTERISTIC OF GAUGE OUTPUT SIGNAL Russian patent published in 2015 - IPC G01B7/16 

FIELD: electricity.

SUBSTANCE: gauge is connected to high-resistance load R_L>500kOhm, initial unbalance and output signal of the gauge is measured at temperature t₀, as well as temperatures t⁺ and t^-corresponding to the upper and lower limit of the operating temperature range. Temperature coefficient of frequency is calculated for bridge measuring circuit $${\alpha }_{do}^{+}$$ and $${\alpha }_{do}^{-}$$ at temperatures t⁺ and t^- respectively as well as non-linearity of temperature coefficient of frequency for the bridge measuring circuit $$\left(\Delta {\alpha }_{do}={\alpha }_{do}^{+}-{\alpha }_{do}^{-}\right).$$ Input resistance is measured for bridge circuit of the gauge. Thermally independent process resistor R_m=0.5·R_in is switched on. Initial unbalance and output signal of the gauge is measured at temperature t₀, t⁺ and t^-. Temperature coefficient of frequency is calculated for input resistance at temperature of t⁺ and t^-. Resistor R_m is switched off. Thermally independent process resistor R_αmin, which rate value is more than permissible values of compensatory thermally dependent resistor R_αin, is mounted to power supply diagonal of the bridge circuit. Initial unbalance and output signal of the gauge is measured at temperature t₀, t⁺ and t^-. Temperature coefficient of frequency is calculated for process thermally dependent resistor R_αmin at temperature t⁺ and t^-. When temperature coefficient of frequency (TCF) of the bridge circuit and its non-linearity belong to the area of TCF positive non-linearity of the bridge circuit to negative one, then rate value of thermally independent resistor R_i is accepted as 0.1·R_in, rate values of resistors R_αin and R_din are calculated. Process thermally dependent resistor R_αmin is replaced by resistor R_αin by partial involvement of resistor R_αmin. Input resistance of the bridge circuit is shunted with resistors R_αin and R_din intercoupled in series. Resistor R_i=0.1·R_in is switched on to power supply diagonal of the bridge circuit. Output resistance R_out is measured for bridge circuit of the gauge. The gauge is coupled to low-resistance load R_l=2·R_out. Initial unbalance and output signal of the gauge is measured at temperature t₀, t⁺ and t^-. Measurements are repeated upon shunting of output resistance of the bridge circuit by thermally independent resistors R_sh=R_out. TCF of the bridge circuit is calculated upon conversion of TCF non-linearity of the bridge circuit $${\alpha }_{do}^{\text{'}+}$$ and $${\alpha }_{do}^{\text{'}-},$$ temperature resistance coefficient (TRC) is measured for the bridge circuit at temperature of t⁺ and t^- respectively as well TCF non-linearity of the bridge circuit $$\Delta {\alpha }_{do}^{\text{'}}={\alpha }_{do}^{\text{'}+}-{\alpha }_{do}^{\text{'}-}.$$ Thermally dependent process resistor, which rate value is more than permissible values of compensatory thermally dependent resistor R_αout, is mounted to power supply diagonal of the bridge circuit. Initial unbalance and output signal of the gauge is measured at temperature t₀, t⁺ and t^-. TCF is calculated for process thermally dependent resistor R_αmout at temperature t⁺ and t^-. If $${\alpha }_{do}^{+\text{'}}$$ and $$\Delta {\alpha }_{do}^{\text{'}}$$ belong to the compensatory area of multiplicative temperature error considering negative TCF non-linearity of the bridge circuit, then rate value is calculated for thermally dependent resistor R_αout and thermally independent resistor R_dout. Process thermally dependent resistor R_αmout is replaced by resistor R_αout by partial involvement of resistor R_αmout. Resistor R_αout is shunted by thermally independent resistor R_dout.

EFFECT: higher accuracy of compensation.

2 cl, 1 tbl