HP 3457A Service Manual page 48

Operation 3457A
3-22. Integration Time. The Integration time can be changed to reduce measurement noise or to permit
faster readings. The integration time is dependent upon the power line frequency and is expressed in num-
ber of power line cycles (NPLC). There are six integration times available; 100 PLC, 10 PLC, | PLC, .1 PLC,
005 PLC and .0005 PLC. The greater the PLC number, the quieter and more accurate the reading will be
and the slower the measurement speed.
© To select the Integration Time - Press the NPLC / A configuration key. Use the [/AUTO or |/HOLD
scroll key to display the desired number and press the ENT / LAST ENTRY key.
The Integration Time can also be changed by pressing the NPLC/A key, entering the desired number directly using the
MATH keys and pressing the ENT/LAST ENTRY key.
3-23, Input Connections. For 2-Wire Ohms measurements, the unknown resistance is connected to the
INPUT HI and LO terminals. This applies to both front and rear terminal operation. When using one of the
optional Plug-In assemblies, the input would be connected to the HI and LO inputs of a particular channel.
For 4-Wire Ohms measurements, the unknown resistance is connected to the INPUT HI and LO terminals
and to the Q SENSE HI and LO terminals as shown in Figure 3-1. When using the HP 44491A General
Purpose Multiplexer assembly, the unknown resistance is connected as shown in Figure 3-2.
Figure 3-1. Front Panel Connections Figure 3-2. Plug-in Connections
3-24. Front/Rear Input Selection. The Input configurations are Front Terminals, Rear Terminals/Scanner
or Open. Only one input configuration (front, rear, scanner or open) can be selected at a time.
© To select Input configuration - Press the TERM / M configuration key. Use the {/AUTO or |/HOLD
scroll key to display the desired input and press the ENT / LAST ENTRY key.
The input can also be changed by pressing the TERM/M key, entering the appropriate number using the MATH keys and
pressing the ENT/LAST ENTRY key.
3-25. Current Measurements (Manual Operation)
3-26. Function Selection. The measurement function is selected by pressing the appropriate function key.
The current measurement functions available are DC Current, AC Current and DC Coupled AC Current.
© To select DC Current - Press the DCI function key.
© To select AC Current - Press the ACI / ACDCI function key.
® To select DC coupled AC Current - Press the Blue SHIFT key then the ACI / ACDCI function key.
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