某温度检测系统以100Ω铂电阻(Pt100)为温度传感器,需1mA 高精度恒流源为其供电,并以6位半数字电压表检测Pt100两端电压作为环境温度信号使用。要求Pt100一端接地。恒流源技术指标如下: 供电电源:220V±10％输出电流:DC1mA 恒流精度:0.01％/24h(24小时允许波动0.1μA) 环境温度:5～45℃要求电路尽可能简单、可靠。请提供电路图,元 A temperature detection system with 100Ω platinum resistance (Pt100) as the temperature sensor, 1mA precision constant current source for its power supply, and a 6 half digital voltmeter to detect the voltage across Pt100 as the ambient temperature signal. One end of Pt100 is required to be grounded. Constant current source technical indicators are as follows: Power supply: 220V ± 10% Output current: DC1mA Constant current accuracy: 0.01% / 24h (24 hours allowed to fluctuate 0.1μA) Ambient temperature: 5 ~ 45 ℃ Circuit as simple and reliable as possible. Please provide the circuit diagram, yuan