Using electronic diagram below can be built a simple metal detector. This detector will help you find objects composed of materials with relatively high magnetic permeability and also indicate if the object inside the detector coil is good or bad conductor properties
Metal detector is powered symmetrical from two 9V batteries, each loaded with about 15 mA. Detector coil L1 is part of sinusoidal oscillator built around transistor T1.
Using this circuit diagram can be built an electronic interface for measuring temperature using a digital multimeter. Temperature sensor interface is very simple, and is built using operational amplifiers and some other electronic components.
Size of the input signal can be measured from the input power.
When is used as a sensor a LM35 and an LM358 type ao at a supply voltage of 5V current is 0.65mA, 0.7mA at 10V, and at a voltage of 15V current is 0.77mA.