VTI Instruments Corp.
70 Basic EX1200 DMM Operation
DMM INPUT CONNECTIONS
Front Panel Connector
The EX126x DMM’s hardware interface is made available on the front panel of the instrument.
The DMM front panel has the following features: five banana jack inputs, a fuse, and three status
LEDs as seen in Figure 4-1 (LED operation is detailed in the LED Indicators section of Section 3).
FIGURE 4-1: INPUT PIN LOCATIONS AND SIGNALS
Standard banana plugs can be used to interface other external instruments with the DMM. The
fuse located on the front panel is for current input protection and is user-replaceable. It is a 3.15 A,
250 V fuse and can be replaced with VTI P/N: 35-0054-315.
NOTE Use sheathed-type probes for voltage and current measurements at the front panel of DMM.
Rear Panel Connector
EX126x mainframes provide an onboard DMM with a five-line analog bus routed through the
backplane to the DMM. This bus is available through rear panel DMM Bus connector that can be
used to extend the analog backplane to other EX1200 series mainframes. To ensure high signal
integrity, environmental noise and cable length should be accounted for prior to routing these
lines.
CAUTION When voltages are switched across the backplane using a multiplexer or matrix switch card, these
voltages are present on the DMM Bus connector. Caution must be observed when handling this
connector.
Also, when the DMM bus is extended to other EX1200 mainframes, the user must ensure that no
two devices are using the bus simultaneously.
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