IBM 7220, Инструкция по эксплуатации

Страница: 32 / 155

3-16
Chapter 3, TECHNICAL DESCRIPTION
3.12.05 Auto-Measure
This function only operates when the reference frequency is greater than 1 Hz. It
performs the following operations:
The line filter is disabled, AC coupling is established, the voltage measurement
mode is entered, with the single-ended A input mode, the FET input device is selected
and the FLOAT mode is set. If the reference frequency is more than 10 Hz the output
time constant is set to 100 ms, otherwise it is set to the lowest synchronous value, the
filter slope is set to 12 dB/octave, output expand is switched off, the reference
harmonic mode is set to 1, the X offset and Y offset functions are switched off and the
Auto-Phase and Auto-Sensitivity functions are called. The Auto-Sensitivity function
also adjusts the AC Gain if required.
The Auto-Measure function is intended to give a quick setting of the instrument
which will be approximately correct in typical simple single-ended measurement
situations. For optimum results in any given situation, it may be convenient to start
with Auto-Measure and to make subsequent modifications to individual controls.
3.12.06 Default Setting
With an instrument of the design of the model 7220, where there are many controls
of which only a few are regularly adjusted, it is very easy to overlook the setting of
one of them. Consequently a Default Setting function is provided, which sets all the
controls to a defined state. This is most often used as a rescue operation to bring the
instrument into a known condition when it is giving unexpected results. A listing of
the settings which are invoked by the use of this function can be found in appendix F.