HP 3457A Service Manual page 50

Operation 3457A
3-32. Frequency/Period Measurements (Manual Operation)
3-33. Function Selection. The measurement function is selected by pressing the appropriate key. The func-
tions available are Frequency and Period.
© To select Frequency - Press the FREQ / PER function key.
© To select Period - Press the Blue SHIFT key then the FREQ / PER function key.
3-34, Range Selection. The HP 3457A has an Auto-Range feature which automatically selects the proper
range to measure the signal applied.
3-35. Measurement Resolution. Measurement Resolution is changed by selecting the number of digits dis-
played. You can choose a display of 3 1/2, 4 1/2, 5 1/2 or 6 1/2 digits. The 1/2 digit refers to the most sig-
nificant digit which is limited to a value of 0, 1, 2, or 3. The default number of digits displayed is 5 1/2
(most significant digit plus 5 digits).
© To change the number of digits displayed - Press the DIGITS DISP / P configuration key, enter the
number 3, 4, 5 or 6 and press the ENT / LAST ENTRY key.
3-36. 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.
3-37. Input Connections. For frequency/period measurements, the input signal is applied 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 is connected to the HI and LO inputs of a particular channel.
3-38, 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.
3-39. HP 44491A General Purpose Multiplexer (Manual Operation)
3-40, The HP 44491A General Purpose Multiplexer has eight 2-wire input channels numbered 0 through 7
and two current/actuator channels numbered 8 and 9. The 2-wire input channels can also be configured as
four 4-wire input channels, In this configuration the input channels are numbered 10 through 13.
3-41. Measurement Selection. Determine the type of measurement you wish to make (Voltage, Resistance,
Current, Frequency/Period) and set the instrument for that measurement as described in the previous
paragraphs.