Building one is a very practical way of going about it. You will be surprised at what kind of everyday household items can be used to build this kind of tester. Materials include laser pointers, rulers, drills, electrical tape, microphones, photo transistors found inside a computer mouse, batteries and clay. It can also involve more specific and advanced pieces of hardware such as phototransistors, experimenter boxes, circuit boards and digital audio editing software.
You can go about building your own tester in several ways. One of the easiest and most practical ways is by building a device box and connecting it to a microphone which then sends sound signals to a sound editing program like Audacity, CoolEdit shareware or Music Morpher. To build the device, you just need a photosensitive transistor, a resistor, a switch, a 1.5V battery, a cable and a box that will contain all of these parts. This device box is a simple and cheap way of measuring the speed of your shutter. It doesn’t work alone, though.
To use this kind of tester, you must place a light source like a light bulb in front of your camera’s lens, open the back of your camera and place your device box near your camera’s shutter. You must also make sure that your device box is connected to your computer’s microphone input and your digital audio editing software is running. Once all of these things are ready and your device box is in place near your shutter, you can turn the device box on. Doing this will produce sound waves that you can see in your digital audio workstation’s recording tool. You must then press the shutter. This will produce the sound that will then be captured by your device box. This specific sound will produce two peaks on your digital audio recording software. One of the peaks represents your shutter in an open state while the other represents your shutter in a closed state. The difference and timing between these two peaks are now your exposure time.
To see the full steps and illustrations, check out this great post by Pablo Martinez Diaz.
You can basically try all types of setups with the basic principle of measuring the sounds of the shutter in two different states, namely its open and close states. If you do not have the skills and the patience to play around with electronics and other unusual items for camera equipment testing, you can always use the good old TV.