For an electronic pocket scale, it is not enough fo […]
For an electronic pocket scale, it is not enough for a high-precision strain sensor to form a bridge measuring circuit with four strain gauges alone. Due to the influence of factors such as process and temperature changes, the sensor is bound to produce certain errors.
The initial unbalanced output of the zero-load output temperature compensation sensor when it is not under load can be adjusted to within the tolerance after the initial unbalance compensation. However, due to the temperature change, the zero-point output of the sensor will also drift, which is referred to as zero-point drift. The main reasons for the zero point drift are that the temperature coefficients of the resistance of each strain gauge are inconsistent, and the linear expansion coefficients of the strain gauges, strain glue, and elastic elements do not match. The length of the lead wire of the film varies. In order to improve the precision and temperature stability of the pocket electronic scale, temperature compensation is necessary. The temperature compensation method of zero-load output is to insert a temperature-sensitive resistor in series in a bridge arm of the bridge circuit and connect the zero-load temperature compensation resistor rt to the bridge arm with a small temperature coefficient according to the drift size and polarity. The temperature compensation resistor rt is generally made of pure copper or pure nickel wire with a large temperature coefficient of resistance. After compensation, the zero drift error of the sensor can be reduced to 0.03%/10°C of the full scale within a few tens of °C.