Keychain Voltmeter

Build

Instructions for building this tool at . The anticipated cost of materials to build this tool is Less than $20. It may take A few hours.

About this tool
Description	Simple and handy voltmeter used to check DC voltage ranges from 3v - 30v without any additional power supply. 3V - 30V DC This tool is recommended for lending libraries.
Ideal Age Group	Elementary school (6 - 10 years), Middle school (11 - 13 years), High school (14 - 17 years), College, Graduate students, Adults, Families, Seniors (Whenever we go outside, there may be need of a voltmeter. We may not carry the traditional voltmeter every time. Sometimes, we may forget or we cannot carry simply due to its size. So, I had a thought to make a tiny voltmeter as a key chain. While going outside we will carry at least 1 key. It may be either a vehicle's or a house key. That's why I made the voltmeter as a key chain.)
Use considerations	Assembly is required. Callibration is required. This tool relies on lab processing. This tool require consumable materials (e.g. batteries, light bulbs, etc.).
Size & weight	Flat: This tool would fit in an envelope. Less than 13oz (a full soda can weighs a little less than 13oz)
Expected lifetime	Should last more or less forever
Topics	Science Policy
Activities	At home, At a science center, zoo or aquarium, In the car, Emergency Response
Tool updated	May 1, 2017, 7:11 a.m.