g .
. Low Pass or High Pass Fi lte r with Doub l ed Ro l l off
The two channel s of the instrument may be cascaded as shown in Fig . 2-11. The
Cutoff Frequencies of both channels are set to the same va l ue and both channels
are set to either High Pass, or Low Pass . F lat Ampl itude response is uti l ized i n
both channels. Signal and channel connections are made as described under
Band-Pass F i l ter and gain settings should a lso be made in accordance with the
instructions given under Band-Pass Filter.
The overa l l respanse of this configuration may be determined by combining the
nonmalized plots given in Figures 2-3 through 2-6 . The Response at the C utoff
F requency wi l l now be 6 dB down and Rol loff wi l l be 48 dB/octave for Mod e l
452 and 96 dB/octave for Made l 852 .
2 -7 .
OUTPUT S IGNAL
F ul l -sca l e output signal is specifi ed as ± 10 Volts and ± 15 mA , max . Above 300 K H z ,
the output signal w i l l fol l ow the reduction i n i n put signal shown i n Fig . 2-2,
provided the current required by the load conne cted to the i nstrument does not
exceed the maxi mum value of ± 15 mAo Heavy capacitive l oads can easily exceed
this current at high frequencies . For example, 25 feet of RG-58 cabl e
is equiva lent to a capacitance of 750 pf, which requires ± 15 mA current a t 300 K H z .
2 -8.
CUTOFF F REQUE N CY OVERRA N GE
The unmarked position between 0 and 10 on the Cutoff Frequency dials is an acti ve
position corresponding to the digit 11. I f a l l Cutoff Frequency dials are set to th is
position a maxim um setting of 122 . 1 (110 + 11 + 1 . 1) is avai l ab l e .
This position provides a 1 0% overrange relative to the specified maximum setting
of 111
•
2 -9 .
M I N I M U M C UTOFF F REQUENCY S ETTI NG
The minimum val i d setting of the Cutoff Frequency dials is 0 . 01. The setting 0 . 00
i s not val id .
2-10
CUTOFF FREQUE N CY RES OLUT I ON
The Cutoff F requency dials shou ld a lways be set for maximum resolution . For exampl e,
a cutoff frequency of 500 H z may be set as 5 . 00x1 00, 0 .50x1 K , or 0 .05x1 OK . Of
the above choices, 5 . 00x100 is the proper setting .
2- 10
