Table of Contents
Advertisement
Figure 5-60, Main Display - Dual Harmonic Mode
In dual harmonic mode, controls and displays relating to the first detection harmonic
carry the suffix "1" and those for the second, the suffix "2". Hence, for example, if a
reference frequency of 1 kHz is applied, Harmonic 1 is set to 3 and Harmonic 2 to 5,
the instrument will measure signals at both 3 kHz and 5 kHz. The Sensitivity 1, Time
Constant 1 and Harmonic 1 Phase controls will affect the signal being measured at
3 kHz, while the Sensitivity 2, Time Constant 2 and Harmonic 2 Phase controls will
affect the signal being measured at 5 kHz.
The range of controls that can be placed on the left-hand side of the Main Display
using the Select Control key is therefore extended to include those relating to both
harmonics of the reference, as follows:-
SENSITIVITY 1 and SENSITIVITY 2
When set to voltage input mode, using the Signal Channel menu, the instrument's
full-scale voltage sensitivity may be set to any value between 2 nV and 1 V in a
1-2-5 sequence.
When set to current input mode, using the Signal Channel menu, the instrument's
full-scale current sensitivity may be set to any value between 1 pA and 1 µA (wide
bandwidth mode, or 10 fA and 10 nA (low-noise mode), in a 1-2-5 sequence.
The number reported after the letters DR is the instrument's Dynamic Reserve,
expressed in decibels, as calculated by the following equation:-
DR
20
log
10
SEN
Example:-
If AC Gain = 12 dB and SEN = 2 mV then
DR
20 log
10
0.002
DR = 46 dB
TIME CONSTANT 1 and TIME CONSTANT 2
The time constant of the output filters is set using this control, in the range 10 µs to
Chapter 5, FRONT PANEL OPERATION
2
ACGain (in dB)
2
14
5-79
Advertisement
Table of Contents
