Stanford Research Systems DS335, Руководство пользователя

Страница: 66 / 86

4-20 Calibration
DS335 Synthesized Function Generator
Bessel Filter Adjustment This adjustment sets the bandpass of the DS335's Bessel waveform filter.
1) Set the DS335 to RAMP waveform, 8 Vpp, 10 kHz frequency. Connect
the DS335's output to an oscilloscope with a 50W terminator. Set the
DS335 for 50
Ω
Load Impedance. Set the scope to 2 V/div vertical and
200 ns/div horizontal.
2) Adjust C542 to make the output rise time as fast as possible while
minimizing the peak-to-peak ripple.
CALIBRATION
The DS335 is fully calibrated at the factory with all calibration bytes secured
in ROM and RAM. The user can change the calibration bytes in RAM after
changing the position of the calibration jumper JP200. The list of calibration
bytes on page 6-2 shows the address and function of every byte. The only
calibration byte that might need adjustment as the instrument ages is the
frequency reference byte. The following procedure describes the adjustment
of the DS335's clock calibration calbyte. In the case where the calibration
bytes in RAM get corrupted, the user can recall the factory calibration bytes.
Please refer to page 6-1 for that procedure.
Allow the DS335 at least 1/2 hour warmup before beginning calibration. All
calibrations should be done with the DS335 completely assembled and 1/2
hour of warmup after reassembly. When the new calbyte values are
determined they should be entered into the DS335's RAM.
Clock Calibration This procedure sets the frequency of the DS335's internal 10 MHz clock.
The procedure is identical for standard and optional oscillators. Be sure that
the DS335 has been completely reassembled and warmed up for at least 1/2
hour before this calibration is started.
1) Connect the DS335's Function output to the frequency counter input with
a 50W terminator. Use the frequency standard as the counter's
timebase.
2) Adjust the value of calbyte 0 so that the frequency is within 1 Hz of 10
MHz (0.01 Hz for optional oscillators). The range of calbyte 0 is 0 to
4095.