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, the initial offset is measured, as well as the output signal at normal temperature t₀, and also temperatures t⁺ and t^-, corresponding to the upper and lower limit of the working temperature range. The temperature coefficient of frequency of the bridge circuit $${\alpha }_{do}^{+}$$ is calculated, and $${\alpha }_{do}^{-}$$ at temperatures t⁺ and t^- accordingly, and also non-linearity of the temperature coefficient of frequency of the bridge circuit. They measure the input resistance of the bridge circuit of the sensor. The heat independent resistor is started R_minp=0.5·R_inp. The initial offset and the output signal of the sensor is measured at temperatures t₀, t⁺ and t^-. The temperature coefficient of resistance of the input resistance is calculated at temperatures t⁺ and t^-. The resistor R_minp is disconnected. The heat-dependent process resistor R_αminp, the rated value of which is more than values of the compensation heat-dependent resistor R_αinp, is installed into a power supply diagonal. They measure the initial offset and the output signal at temperatures t₀, t⁺ and t^-. The temperature coefficient of resistance is calculated for the process heat-dependent resistor R_αminp at temperatures t⁺ and t^-. If $${\alpha }_{do}^{+}$$ and $$\Delta {\alpha }_{do}^{\text{'}}$$ belong to the area of transformation of the positive non-linearity of the temperature coefficient of frequency of the bridge circuit into negative one, then they calculate the rated value of the resistor R_αinp. The process heat-dependent resistor R_αminp is replaced with the resistor R_αinp by partial engagement of the resistor R_αminp. They measure the output resistance of the bridge circuit of the sensor R_outp. The sensor is connected to the low-Ohm load R_l=2·R_outp. The heat-dependent process resistor R_αmoutp, the rated value of which is more than possible values of the compensation heat-dependent resistor R_αout, is installed into the output diagonal of the bridge circuit, accordingly. At temperatures t₀, t⁺ and t^- they measure values of both the initial offset and the values of the output signal of the sensor at the nominal value of the measured parameter. Into the output diagonal they connect serially with the load a heat-independent resistor R_m1=R_outp, repeat measurements of initial offset and output signal of the sensor. The resistor R_m1 is replaced with the resistor R_m2=2·R_out, measurements of the initial offset and the output signal of the sensor are repeated. The resistor R_m2 is disconnected, values of the temperature coefficient of resistance are calculated for the output resistance, the resistor, temperature coefficient of frequency of the bridge circuit after transformation of the temperature coefficient of frequency of the bridge circuit $${\alpha }_{do}^{\text{'}+}$$ and $${\alpha }_{do}^{\text{'}-},$$ as well as non-linearity of the temperature coefficient of frequency of the bridge circuit $$\Delta {\alpha }_{do}^{\text{'}}={\alpha }_{do}^{\text{'}+}-{\alpha }_{do}^{\text{'}-}.$$ . If $${\alpha }_{do}^{\text{'}+}$$ and $$\Delta {\alpha }_{do}^{\text{'}}$$ 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, then the rated value of the heat-dependent resistor R_αoutp and the heat-independent resistor R_∂are calculated. The process heat-dependent resistor R_αmout is replaced with the resistor R_αoutp by means of partial engagement of the resistor R_αmoutp. The resistor R_αoutp is shunted with the heat-independent resistor R_∂.

EFFECT: increased accuracy of compensation of multiplicative temperature error.

2 cl, 1 tbl