Mode! 21 is a closed-loop, frequency stabilized, function
generator. Both short term and long term frequency
accuracies are 0.09% over its 100 ^Hz to 11 MHz frequency range.
Modes are continuous, triggered and gated. Output levels are
to 20V peak-to-peak (10 Vp-p into 5052).
Waveforms are sine, triangle, square, ramp up, ramp down,
haversine, havertriangle and dc. Above 1,1 kHz waveforms are
analog generated; below, waveforms are digitally
synthesized. Synthesized waveforms can be held at any point
and continued from that point.
Synthesized output signal frequency is 1/1000 of reference
clock frequency, which can be internal or external. By use
of an external reference clock, the output range can be
extended to ultra-low frequencies.
An LCD display shows frequency (3Vz digits plus unit of
measure) and annunciators that indicate selected operating
modes, etc. Output is reverse power protected.
1.2.1 Versatility Waveforms
A bidirectional switch selects sine , triangle, square and
dc. For frequencies below
1.100 kHz ramp up, ramp down and haver-waves are also available.
Continuous: Generator runs continuously at selected frequency.
Triggered: Generator is quiescent until triggered by
external signal or manual trigger, then generates one
complete waveform cycle at selected frequency.
Gated: As triggered mode, except output continues for
duration of gate signal. Last waveform started is completed.
100 piHz to 11 MHz in 9 overlapping decade ranges. Range
switching with bidirectional switch with frequency digits;
decimal and units displayed on LCD display. Each decade
range capable of 1100:1 frequency change controlled by the
Frequency Coarse and Fine controls.
Waveform amplitude variable over a 20 dB range up to 20 Vp-p
(10 Vp-p into 50Q) at Function Out. Waveform also present at
Function Out (-20 dB) with a fixed 20 dB attenuation
relative to the Function Out for a full 40 dB of amplitude
range. Peak output current is 100 mA maximum at Function
Out. Source impedance of both outputs is 50Q.
DC Offset and DC Output
Waveform offset and dc output variable with DC Offset
control with off position for calibrated zero offset.
Function Out is ± 10V maximum (± 5V into 50Q) as offset or
Vdc output. Signal peak plus offset limited to ± 10V(±5V
into 50S2). DC offset plus waveform attenuated
proportionately at Function Out (-20 dB).
TIL pulse (50 % duty cycle) at Generator frequency wifi
drive 10 LS TTL loads.
VCG — Voltage Controlled Generator
Up to 1100:1 frequency change with external 0 to ± 5V signal
applied to VCG IN connector. Upper and lower frequencies
limited to maximum and minimum of selected range. Input
impedance is 5kΩ and maximum slew rate is 0.1 V/µs. VCG IN
is disconnected when the Stabilizer is engaged.
Trigger and Gate
External TTL compatible signal at Trig In BNC triggers or
gates Generator output when Generator is in trigger or gate
mode. Generator triggers on positive edge of input or gates
on for duration of high level input. External signal pulse
width is 50 ns minimum with a maximum repetition rate of 5MHz.
When selected, the Generator frequency is stabilized at the
displayed frequency to a crystal-controlled reference. The
Stabilizer improves long term frequency stability for all
durations to be equal to the 10 min. short term value.
When the stabilizer is on, the Generator frequency is
corrected to the displayed frequency ±0.09% of rangeover the
entire operating temperature range of 0 to 4- 50°C. The
stabilizer is automatically turned off when the mode is
taken out of continuous or Ext Ref. is enabled.
1100 count LCD frequency display with frequency ranging
units(mHz, Hz, kHz, and MHz)and decimal point. Annunciators
indicate selection of waveform, stabilizer and external
reference status, haverwave selection and Generator mode.
External Reference switch provides selection of internal or
external control of waveform output frequency and also
provides a means of holding or releasing the waveform
manually, electrically or through external contact closure.
External Reference connector accepts either aTTL compatible
signal (1.1 MHz maximum repetition rate, 200 ns minimum
pulse width) or contact closure. External reference provides
four modes of operation.
Int Ref: Normal waveform function Generator operation when
in internal reference and the Ext Ref BNC is either left
unconnected or connected to + 5 Vdc or aTTL high.
Ext Ref: External Reference operation by applying frequency
to the Ref In BNC with external reference selected.
Frequency input controls frequency of the selected waveform
at the output. The output frequency will be 1/1000 the
reference frequency. Maximum output frequency is 1.100 kHz.
When external reference is selected, the display is disabled
Manual Hold: At any point on the output waveform by use of
the Ref button. Reference mode must be “Int Ref” as above.
When Ref button is pressed, the output is stopped. When
pressed again, the waveform will start again exactly where
Electrical Hold: At any point on the output waveform:
When in “Int Ref” operation and 1.100 kHz or below, hold the
waveform by applying 0 Vdc or a TTL low to the Ext Ref BNC
or through remote contact closure shorting out the BNC.
When in “Ext Ref” operation, hold the waveform by removing
the external signals at Ext Ref BNC or bringing it to 0 Vdc.