You need to do a little DIY and run some cables to the extension upstairs, but are more than a little concerned about hitting some power cables with your trusty drill. With a portable ammeter you can quickly and easily check a wall for current before you drill, making sure you are safe while knocking all of those holes in your walls. An ammeter is a simple measuring instrument that is useful for locating and measuring electrical circuits. Electric currents are measured in amperes, which is how the device came by its name. If you want to get the job done as quickly and efficiently as possible, a digital ammeter can give you a simple digital reading in seconds. If you are something of a purist and like to get your hands on old-fashioned tools, you can also find a vintage ammeter that may be a little more cumbersome to use, but really looks the part. No matter for which type of tools you are looking, be they new, used, or vintage, you can rely on the wide selection on eBay for everything you need.