Service manual

Test 2-2: DC
Isolation Test
This test verifies that sufficient DC isolation exists at various points on the
multiplexer. DC Isolation is checked from HI to Chassis, HI to LO, and HI
to GU (GUARD). This test uses the test fixture (see Figure 2-1).
NOTE
The DMM used should be capable of measuring at least 1 G.
Ω. If the
DMM indicates an overload, record the reading as >Rmax, where Rmax is
the highest resistance that the DMM can measure. For example, if the
DMM is an Agilent 3458A, a typical return for an overload is 1.E+38 and
the entry in Table 2-2 should be >1.2 G
Ω.
HI to Chassis Isolation 1. Make hardware connections as shown in Figure 2-9
2.
Set DMM to 2-wire ohms, 1 G Ω range
3. Send CLOS (@100,108,116,193) to close all Tree relays
4. Trigger the DMM with TRIG SGL
5. Record the DMM reading on Table 2-2 (HI to CHASSIS)
HI to LO Isolation 1. Make hardware connections as shown in Figure 2-10
2. Trigger the DMM with TRIG SGL
3. Record the DMM reading on Table 2-2 (HI to LO)
Figure 2-9. HI to Chassis Isolation Connections
2-16 Verification Tests