9
TG215/TG230:
with DISPLAY SELECT set to DC offset, the offset level of the MAIN output is
displayed. The display shows open circuit voltage offset (emf); the actual voltage at the socket
will be half the displayed value when the output is terminated with its characteristic impedance.
Aux Output
The AUX output provides a fixed 0 to 5V TTL/CMOS pulse output at the same frequency,
symmetry and phase as the 50
Ω
MAIN output and is capable of driving 4 standard TTL loads.
Sweep Input
The generator frequency can be swept, DC programmed or modulated by a suitable control
voltage applied to the SWEEP IN socket. The instrument sums the SWEEP IN voltage with the
internal control voltage derived from the FREQUENCY vernier to determine the operating
frequency. With the DISPLAY SELECT switch in the frequency position on TG215/TG230, the
display shows the resultant frequency. A positive voltage increases the frequency; for frequency
control with positive-going DC inputs the vernier should therefore be set to the lower frequency
limit of the range to be swept. For example, a 0V to +3V signal will sweep the generator 3
decades up from range minimum, set by the vernier, to range maximum.
Similarly, a negative voltage decreases the frequency and for negative-going DC inputs the
vernier should be set to the upper frequency limit of the range to be swept. For example, a 0V to
-3V signal will sweep the generator 3 decades down from range maximum, set by the vernier, to
range minimum.
To use a sweep signal which is symmetrical about ground, the vernier should be set to give a
frequency at approximately the centre of the band to be swept.
Note: Non-linear operation may result when the sweep input voltage is excessive; that is, when
the attempted generator frequency exceeds the range limits.
Sweep Mode Operation (TG230 only)
With sweep ON, achieved by pulling the RATE control knob to the out position, the output of the
internal sweep generator is summed with the FREQUENCY vernier.
Frequency Selection
Using the FREQUENCY RANGE switches, select the lowest range within which the upper sweep
limit can be set; in this way the best setting resolution and the widest sweep range can be
realised. Select LIN or LOG as required with the STOP control knob; in is LIN and out is LOG.
Sweep Limits
To accurately set the sweep limits on the TG230 proceed as follows:
Set the STOP control to minimum (fully anticlockwise).
Pull out the RATE knob to set sweep on and select LIN or LOG with the STOP knob.
Hold in the SET START button and set the START (lowest) frequency on the display using the
FREQUENCY vernier; the START frequency must be set first. Now release the SET START
button, hold in the SET STOP button and set the STOP (highest) frequency on the display using
the STOP control; release the SET STOP button. Note that both the FREQUENCY vernier and
the STOP control have a log characteristic when LOG mode is selected.
The sweep limits can be checked at any time by depressing the SET START or SET STOP
buttons.