Adjusting Notch Filters - Stanford Research Systems SR850 User Manual

SR850 Service
Adjusting the Notch Filters
1. The Notch filter frequency and depth adjustments must be done together. This procedure requires
a BNC cables. A small slotted screwdriver is also required to adjust the potentiometers.
2. Turn the unit ON while holding the [<-] key down. This resets the unit. Let it warm up for at least
an hour.
3. Remove the four black screws which secure the top lid. There are two screws on each side. Slide
the top lid back about 1/4". Remove the lid by pulling the lid towards the back and upwards.
4. The adjustment pots are on the Analog board on right hand side of the card cage. The notch filter
adjustments are accessible through the card cage vent holes. Do not remove the card cage
cover.
5. The adjustment pots are shown in the figure.
The Notch Frequency and Notch Depth adjustment
pots are outside the shield which is mounted on the
analog board.
6. Connect the SINE OUT output to the A input with a BNC cable.
Press the following keys to set the frequency, display and time constant.
After the readings are stable, the top display should read 1.00 V (±2%).
[REF/PHASE]
<Ref. Frequency> Select Reference Frequency
[6] [0] [ENTER] Enter 60 Hz OR
[5] [0] [ENTER] Enter 50 Hz
[DISPLAY/SCALE]
<Type/Trace> Select Trace Number for Top display
[3] [ENTER] Enter 3 to display R on the top
<Full/Top/Bottom> to select Bottom display
[4] [ENTER] Enter 4 to display
[GAIN/TC]
<Filter dB/oct> twice to select 24 dB/oct
<Synchronous> to select <200 Hz
DSP
Board
on the bottom
8-6
Analog
Board
2xLine Notch Depth
Line Notch Depth
2xLine Notch Freq
Common Mode
Line Notch Freq
Voltage Input Offset
Current Input Offset
Front