External pattern and internal circuit of ultra-small multimeter

Probe domestic PL75-Q2 big four claw head head nickel plated head diameter is 1.3mm needle outside

The ultra-small multimeter is only 40 x 80 x 17mm and can be easily placed in the pocket of a garment or hung on the waist.
The left part of the figure is the shape of the ultra-small multimeter, and the right part is the internal circuit. The head of the circuit adopts the commonly used 91L16 type 0-300V small voltage meter. The internal resistance of this small meter is 430Ω and the full current is 0.5mA. If the reader's head is not this parameter, it needs to be re Design peripheral component values.
The ultra-small multimeter has six gear positions, which are AC 500V, DC 2.5V, 25V, 250V voltage and R×1KΩ resistance and DC 0.5mA current. The gear position changeover switch K1 is a common two-knife three-position toggle switch, and a single-pole two-position switch K.
With the cooperation function replacement. The battery used in the resistor file is a VR22 type 12V battery. The pen is made of hard and thick wires, and it can also be welded with a pair of small alligator clips. The adjustable zero potential potentiometer uses an adjustable resistor with a plastic cap. The scale of the header needs to be redrawn.