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.