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

FIELD: measurement equipment.

SUBSTANCE: sensor is connected to a load R_l>500 kOhm, initial unbalance and output signal are measured at normal temperature t₀, and also temperatures t⁺ and t^-, corresponding to the upper and lower limit of the working temperature range. Temperature coefficient of frequency for a bridge circuit $${\alpha }_{\partial o}^{+}$$ and $${\alpha }_{\partial o}^{-}$$ is calculated at temperatures t⁺ and t^-, accordingly, as well as non-linearity of temperature coefficient of frequency of the bridge circuit $$\left(\Delta {\alpha }_{\partial o}={\alpha }_{\partial o}^{+}-{\alpha }_{\partial o}^{-}\right)$$ . Input resistance of the bridge circuit of the sensor is measured. A heat-independent resistor R_m=0.5·R_inp is started. Initial unbalance and output signal is measured at temperatures t₀, t⁺ and t^-. The temperature coefficient of resistance is calculated for input resistance at temperatures t⁺ and t^-. The resistor R_m is disconnected. If $${\alpha }_{\partial o}^{+}$$ and Δα_∂o belong to the field of conversion of a positive non-linearity of temperature coefficient of frequency into a negative one, then the nominal of the resistor R_i is calculated. Into the power supply diagonal of the bridge circuit they connect a heat-independent resistor R_i with the calculated nominal. They measure the output resistance of the bridge circuit for the sensor R_outp. The sensor is connected to a low-resistance load R_l=2·R_outp. A heat-independent process resistor R_αm, the nominal of which is more than possible values of a compensatory heat-independent resistor R_α, is installed into the output diagonal of the bridge circuit. Initial unbalance and output signal of the sensor is measured at temperatures t₀, t⁺ and t^-. Measurements are repeated after shunting of the resistor R_αm with a heat-independent resistor R_sh1=1.25·R_αm. Measurements are repeated after replacement of the resistor R_sh1 with a heat-independent resistor R_sh2=0.25·R_αm. The temperature coefficient of frequency is calculated for the bridge circuit after conversion of non-linearity of the temperature coefficient of frequency of the bridge circuit $${\alpha }_{\partial o}^{{\text{'}}_{+}}$$ and $${\alpha }_{\partial o}^{{\text{'}}_{-}}$$ , and also the temperature coefficient of resistance for the output resistance and the temperature coefficient of resistance of the resistor R_αm at temperatures t⁺ and t^- accordingly, and also the non-linearity of the temperature coefficient of frequency of the bridge circuit $$\Delta {\alpha }_{\partial o}^{\text{'}}={\alpha }_{\partial o}^{{\text{'}}_{+}}-{\alpha }_{\partial ou}^{{\text{'}}_{-}}$$ . If $${\alpha }_{\partial o}^{{\text{'}}_{+}}$$ and $$\Delta {\alpha }_{\partial o}^{\text{'}}$$ belong to the area of compensation of the multiplicative temperature error with account of negative non-linearity of temperature coefficient of frequency of the bridge circuit, they calculate the nominal of the heat-dependent resistor R_α and heat-independent resistor R_∂. The process heat-dependent resistor R_αm is replaced with a resistor R_α by partial engagement of the resistor R_αm. The resistor R_α is shunted with a heat-independent resistor R_∂.

EFFECT: increased accuracy of compensation of multiplicative temperature error.

2 cl, 1 tbl