An automatic circuit board tester for testing for shorts, opens, and
interconnected pins or nodes on a circuit board. The tester first
classifies the nodes as being in one of three categories based upon the
design of the board and the intended interconnection of the nodes. The
categories of nodes are: (1) connected to ground; (2) interconnected to
all other nodes in the test group; or (3) isolated from all other nodes.
The circuit board tester has a testhead containing a plurality of test
channels, each configured to be coupled to a node on the circuit board.
The testhead utilizes a digital signal from a digital driver to drive the
node, at a predetermined voltage and a digital receiver to read the node
voltage to determine if it is coupled to ground. Each test channel also
includes a switch to connect the digital driver and receiver to the test
node as well as a ground switch to selectively couple the node to ground.
Various combinations of switch positions and testing sequences enables the
circuit board tester to test all node connections and to ensure that the
physical embodiment of the circuit board accurately reflects the circuit
board design.