CLIOwin 6.5 PCI User's Manual - Audiomatica Srl

13 MEASURING IMPEDANCE AND T&S PARAMETERS
13.1 INTRODUCTION
This chapter deals, before going in the Thiele and Small Parameters Menu description,
with impedance measurements in general. 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 explain now. 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 upon how 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, require only one measure, it is easier to handle the connections
needed.
13.3 INTERNAL MODE
CLIO
INPUT A
INPUT B
OUTPUT A
OUTPUT B
ZX
Figure 13.1
In principle, Internal mode is very similar to Constant Current. Takes advantage on
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 true Constant Current
procedure. Veterans should not worry; Even if the resistor value is on the same order
of magnitude of 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 at
device terminals as complex (real and imaginary). Fig.13.1 shows the connections for
measuring Impedance in Internal mode. Only one cables (pin-to-alligators like the one
in the photo) needed, without any other external active or passive device. 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 127