A Novel Temperature and Pressure Measuring Scheme Based on LC Sensor for Ultra-High Temperature Environment

Abstract

A novel temperature and pressure measuring scheme based on LC sensor for ultra-high temperature environment is presented here. This method resolves the interference of the temperature drift of the HTCC LC pressure sensor and avoids magnetic field crosstalk between two sets of LC circuits. The scheme is that the temperature is expressed by the amplitude of the resonant frequency of an input return loss curve (S11). And then, the temperature and the resonant frequency are combined to calculate the pressure value. According to this idea, the sensor is manufactured. The sensor is composed of high temperature co-fired ceramics (HTCC) substrate and platinum LC circuit based on screen-printing technology. The platinum circuit consists of a planar spiral inductor(L) and four parallel plate capacitors(C). The external antenna is coupled to the inductor of the sensor to form a device whose impedance is measured by the network analyzer to generate an input return loss curve (S11). The testing principle is to utilize the thermistor characteristics of platinum and the pressure-sensitive properties of airtight cavities. The amplitude of the resonant frequency of S11 is mainly affected by the platinum resistance of the sensor, and the pressure has a reduced influence on the amplitude with elevating temperature. The maximum pressure sensitivity measured is 23.735kHz / kPa at 1200°C in the pressure range of 50kPa to 300kPa. The temperature sensitivity is 0.009dB/°C from 25°C to 1200°C. The impedance variation of the sensor and the XRD and SEM analysis of the platinum film conductor were analyzed.