Test Point
A test point is an exposed copper area left deliberately on the board for a measurement probe or a production fixture to contact. It is placed on critical nodes such as supply lines, reference voltages, controller outputs and fault signals; it makes the measurement possible without touching a component lead.
On a board without test points, measurement is done by resting the probe on a component lead. This both carries the risk of accidentally shorting two leads and is not practically possible on fine-pitch parts.
- Service test points: these are the points to be checked with a multimeter in the field; supply, reference voltage and fault line, for example. The manual states what should be read at which point.
- Production test points: these contact the spring-loaded probes in the fixture. They are usually gathered on a single side of the board and on a regular grid.
- Size: for a hand probe, an area of a few millimetres is a comfortable working size; fixture pins can also work with smaller pads.
The value of test points in fault finding is this: with the first few measurements you separate whether the problem is in the supply stage, the logic stage or the output stage. If the expected value ranges of the test points are written in the board's documentation, this separation takes minutes.
The context in which this term is used: Our Services