Introduction - Ametek 7280 Instruction Manual

Front Panel Operation

5.1 Introduction

This chapter describes how to operate the model 7280 using the front panel controls,
and discusses its capabilities when used in this way. Chapter 6 provides similar
information for when the unit is operated remotely using one of the computer
interfaces.
It is assumed that readers are already familiar with the use of the front panel
keys, but if not then they should refer to the detailed description of their operation
given in chapter 4.
The model 7280 uses a flexible, menu-based, control structure which allows many
instrument controls to be adjusted from the front panel with only a few key presses.
Furthermore this design makes it very easy to introduce new features or improve
existing ones without the restrictions which would result from a fixed front panel
layout.
The instrument may be operated in one of four modes, as follows:-
Single Reference
This is the normal operating mode of the unit, where it functions as a conventional
dual phase lock-in amplifier. It includes both internal and external reference modes
and provides detection either at the reference frequency or one harmonic of it.
Virtual Reference
Virtual reference mode is an extension of internal single reference mode operation,
where the Y channel output is used to make continuous adjustments to the internal
oscillator frequency and phase to achieve phase-lock with the applied signal such that
the X channel output is maximized and the Y channel output is zeroed. Virtual
reference mode operation is only possible with signals at frequencies between 100 Hz
and 2.0 MHz.
Dual Reference
In dual reference mode the model 7280 can make simultaneous measurements at two
different reference frequencies, of which one must be external and the other must be
derived from the internal oscillator. In standard instruments, the maximum detection
frequency for either reference
7280/99 option allow operation to 800 kHz and those with the 7280/98 option allow
operation to 2.0 MHz
Dual Harmonic
Dual harmonic mode allows the simultaneous measurement of two different
harmonics of the input signal. As with dual reference mode, in standard instruments,
the maximum detection frequency for either harmonic
units fitted with the 7280/99 option allow operation to 800 kHz and those with the
7280/98 option allow operation to 2.0 MHz
The sections which follow describe the menus as they appear when the unit is being
used in single reference mode. The menus range from the Main Display, used most of
or reference is 20 kHz, but units fitted with the
1 2
Chapter
or harmonic is 20 kHz, but
1 2
5
and
5-1