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

FIELD: instrumentation.

SUBSTANCE: in an output diagonal of a bridge circuit they install a heat-dependent process resistor R_αt, the par value of which is more than possible values of a compensation heat-dependent resistor R_α. In parallel to the resistor R_αt they install a link. Output resistance of the bridge circuit is measured R_out. The sensor is connected to a low-resistance load R_l=2·R_out. Initial unbalance is measured, as well as the output signal of the sensor at normal temperature t₀, and also temperature t⁺, corresponding to the upper limit of working range of temperatures, and t^-, corresponding to the lower limit of working range of temperatures. Measurements are repeated after connection of the sensor to the low-resistance load $$R_l^{\text{'}}=R_{out}.$$ On the basis of measured values of the initial unbalance and the output signal of the sensor, they calculate temperature coefficient of frequency $${\alpha }_{\text{s meas}}^{+}$$ and $${\alpha }_{\text{s meas}}^{-},$$ and temperature coefficient of resistance for the output resistance at temperatures t⁺ and t^- accordingly, and also non-linearity of temperature coefficient of frequency of the bridge circuit ( $$\Delta {\alpha }_{\text{s meas}}={\alpha }_{\text{s meas}}^{+}-{\alpha }_{\text{s meas}}^{-}$$ ). The link is removed from the resistor R_αt. They measure initial unbalance and output signal of the sensor at temperatures t₀, t⁺ and t^-. On the basis of measured values of initial unbalance and output signal of the sensor they calculate temperature coefficient of resistance for the heat-dependent resistor R_αt at temperatures t⁺ and t^-. If temperature coefficient of frequency of the bridge circuit and its non-linearity belong to the area of method application, then they calculate par value of the heat-dependent resistor R_α and heat-independent resistor R_sh. The process heat-dependent resistor R_αt is replaced with the resistor R_α by partial engagement of the resistor R_αt. The output resistance of the bridge circuit is shunted by the heat-independent resistor R_sh.

EFFECT: increased accuracy of compensation.

2 cl