CLIOwin 7 PCI User's Manual - Audiomatica

13 MEASURING IMPEDANCE AND T&S PARAMETERS
13.1 INTRODUCTION
This chapter deals with impedance measurements generally before going onto the Thiele
and Small Parameters Menu description. CLIO performs impedance vs. frequency
measurements both from within the MLS and the Sinusoidal Menu. You will find specific
information in the relative Chapters. Both are relevant to what we will now explain. Here
we explain connections, principles and other topics that apply to both menus.
Differences and choice criteria are also covered.
13.2 GENERALS
Whatever the stimuli, CLIO sees a voltage at its input. Impedance is obtained by a
suitable post process, which changes depending upon how the user decides to perform
the measurement. Four methods are available. Two of them, Internal and I Sense,
were already found in the Settings Dialog, both in MLS and Sinusoidal. We will start with
these, leaving Constant Voltage and Constant Current to later on. The last two
methods derive their name from the description of what is going on during the
measurement; they were the standard before automatic computer based Measuring
Systems. Internal and I Sense are faster, requires only one measurement, and
handles the connections needed much more easily.
13.3 INTERNAL MODE
INPUT A
CLIO
INPUT B
OUTPUT A
OUTPUT B
ZX
Figure 13.1
In principle, internal mode is very similar to Constant Current. It takes advantage of
the knowledge CLIO has of its own output level and output impedance (150 Ohm 0.1%).
In fact, this value is lower than what should be used for a true Constant Current
procedure. Veterans should not worry: even if the resistor value is on the same order
of magnitude as the device you are going to measure instead of 10 times higher as
usually advised, no errors occurs as CLIO is able to acquire and evaluate the signal as
a complex signal (real and imaginary) at the device terminals. Fig.13.1 shows the
connections for measuring Impedance in Internal mode. Only one cable (pin-toalligators
like the one in the photo) is needed, without any other external active or
passive devices. Before starting any impedance measurement in Internal Mode
remember to switch on the loop button ( or ) of the channel you are going to
use.
Chapter 13 - Measuring impedance and T&S parameters 157