RELAY SWITCHING TECHNIQUES
The 20-Node Relay Matrix
The Voltech AT3600 uses a 20-node relay matrix, terminating in pairs of spring probes, to allow standard fixtures to be connected to the unit. Each pair of spring probes (a node) connects to four high-voltage relays, configured for full Kelvin (4-wire) measurement. Two of these relays, 'Source Hi' and 'Source Lo' (the "power" pair), are energized to supply the voltage/current source to the component under test. The remaining two relays, 'Measure Hi' and 'Measure Lo' (the "sense" pair), are energized to route the voltage/current source to the measure circuit. This configuration is shown below, in Figure 1, for one of the nodes connected to one end of a transformer winding under test.
This type of Kelvin relay arrangement for each of the 20 nodes is fully controlled by the AT3600 and is programmable through the supplied AT Editor software. There are no limitations as to which node is used for which transformer winding.
The picture on the right is a screen shot from the AT Editor software. It is a graphical representation of the actual 20-node relay matrix on the AT tester itself. Each numbered node (1-20) represents the four-relay schematic shown in Figure 1 above. There are four relays per node and 20 nodes, totalling 80 relays.