Making Measurements: The Generator 1250 Frequency Response Analyzer
4-4 AMK / 1250 / 4
The exponent must always be expressed with respect to the units in the square
brackets.
Having set the required value plus units and/or exponent in the New Data section,
ENTER must be pressed for the change to be actioned. The Display will again revert to
that shown in Fig. 4.1. If FREQ is pressed again, the new frequency will now appear in
the Current Data section.
Note that the format may have been altered by the transition from New to Current Data
status, e.g. if 0.25 kHz is entered, this will appear as 250 Hz in the Current Data section.
4.2.5 CLEAR
If an error is made whilst keying information into the New Data section, pressing CLEAR
erases the contents of the round brackets. As with "Setting the Waveform", the contents
of the New Data section has no effect on the 1250 settings until ENTER has been
pressed.
4.2.6 AMPLITUDE
Press AMPL. The Display will be similar to Fig. 4.4 for frequency, but show AMPL, with
units of rms voltage. Key in the new amplitude as described for frequency and ENTER.
Note. The 1250N Generator source impedance is low, at approximately 1.5 Ω. So, for
low impedance loads, multiply the amplitude required by a scale factor to get the
amplitude you must program.
The scale factor = load impedance + 1.5
load impedance
4.2.7 BIAS
Press BIAS. The Display will be similar to Fig. 4.4 for frequency, but show BIAS, with
units of dc voltage. As bias can be of either polarity, select the one required by the +/-
key, set the required voltage and ENTER.
4.2.8 MODULATED CARRIER
This is available only when the optional Modulator/Demodulator Unit is fitted in the
1250. Connecting the Unit and the use of the MOD key are described in Chapter 15
"Options". The default state is "off”, so if no unit is fitted, the MOD key is not used.
If an attempt is made to enter any state other than "off" via the MOD key, when no Unit
is present, an Error Code Number will appear in the Display, accompanied by a warning
"beep". The Error Codes are listed in Chapter 11.
This completes the setting up of the basic Generator menu. The remaining facilities
accessible via the GENERATOR MENU key do not need setting up for simple
measurements and are described in later sections.
4.3 CHECKING GENERATOR SETTINGS: USING THE STATUS
DISPLAYS
To cheek that the Generator, or any other section of the 1250, has been set up correctly,
the user could step through all the Menus again. However, a better method is to use the
STATUS key, as described in Chapter 11.
Attention is also drawn to the Mini-Status Display, described in Chapter 7.
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