Service manual

Test 2-1: Closed Channel Resistance Test
This test verifies that all relay contacts meet the closed-channel resistance
specification for the multiplexer. If the closed-channel resistance of any
relay contact is greater than 2Ω, the relay should be replaced. This test uses
the test fixture (see Figure 2-1).
Measuring Protection
Resistors
Since there are 100Ω protection resistors (R20 through R31) in the relay
paths, measure the protection resistor values to begin this test. The values of
the protection resistors are then subtracted from the measured path
resistance to determine the relay contact resistance. To measure the
protection resistor values, set the 3458A DMM to 4-wire ohms, autorange
and measure each resistor value with the DMM (see Figure 2-2). Record the
measured values in Table 2-1.
NOTE
On the E1343A and E1344A, Resistors R22, R25, R28, and R31 are 1.0kΩ
resistors.
Table 2-1. Measured Protection Resistor Values
Resistor
Measured Value (Ω)
Resistor
Measured Value (Ω)
R20
R21
R22
___________________
___________________
___________________
R26
R27
R28
___________________
___________________
___________________
R23
R24
R25
___________________
___________________
___________________
R29
R30
R31
___________________
___________________
___________________
Figure 2-2. Typical Resistance Measurement Connections
24 Verification Tests Chapter 2