Frequent Y /Period Measurements; Hp 44491A General Purpose Multiplexer - HP 3457A Service Manual

Operation 3457A
3-32. Frequency/Period Measurements (Manual Operation)
3-33. Function Selection. The measuremcnl function is selected by pressing the appropriate key. T h e func-
tions available are Frequency and Period.
T o select Freq~lency
-
Press the FREQ
/
PER function key.
T o 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 t o 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 digil refers t o the most sig-
nificant digit which is limited t o a value of 0, 1, 2, or 3. The default number of digits displayed is 5 1/2
(most significant digit plus 5 digits).
T o change the number of digits
displayed -
Press the
DIGITS DISP
/
P
conl'iguration key. enter the
number 3, 4, 5 o r 6 and press the ENT
/
LAST ENTRY hey.
3-36. Integration Time. The Integration time can be changed t o reduce measurement noise o r t o 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, I PLC, .I 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.
T o select the Integration Time
-
Press the NPLC
/
A
configuration key. Use the
?/AUTO
o r
HOLD
scroll key t o display the desired n~lmber and press the ENT
/
LAST ENTRY key.
3-37. lnput Connections. For frequency/period measurements, the input signal is applied t o the INPUT HI
and L O Terminals. This applies t o both Front and Rear Terminal operation. When using one of the optional
Plug-In assemblies, the input is connected t o the HI and LO inputs of a particillar channel.
3-38. Front/Rear lnput Selection. The Input configurations are Front Terminals, Rear Terminals/Scanner
o r Open. Only one input configuration (front, rear, scanner or open) can be selected a t a time.
T o select Input configuration
-
Press the TERM
/
M configuration key. Use the ?/AUTO o r JJHOLD
scroll key t o display the desired input and press the ENT
/
LAST ENTRY key.
The input cart o l t o he chnrtged hy pructirrg tlrr TERM/M k e y , erttwirtg the nl)proprittfe rtrrrtrl~er rrsirtg the M A 1'H k c ) , $ cfrtcl
pressing tlte ENTILAST ENTRY Icey.
3-39. HP 44491A General Purpose Multiplexer (Manual Operation)
3-40. The HP 44491A General Purpose Multiplexer has eight 2-wire input channels nilmbered 0 through 7
and t w o current/actuator channels numbered
8
and
9.
The 2-wire i~lpirt 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 t o make (Voltage, Resistance,
Current, Frequency/Period) and set the instrument for that measurement as described in the previous
paragraphs.