Analog Devices EVAL-AD5933EBZ User Manual page 7

Evaluation Board User Guide
1
Figure 12. AD5933 Evaluation Software Front Panel (Impedance Profile of 200 kΩ Resistor Displayed)
•
Choose the external clock as the system clock. Select
External clock in the System Clock section (see 2 in
Figure 12).
•
Set Output Excitation voltage range of the
Pin 6 (VOUT) to Range1:2v p-p (see 2 in Figure 12). The
four possible output ranges available are 2 V p-p, 1 V p-p,
0.4 V p-p, or 0.2 V p-p, typically.
•
Set the PGA gain of the ADC on the receive stage (either
×1 or ×5) in the PGA Control section to ×1 (see 2 in
Figure 12).
•
Refer to the Calibration Impedance panel (see 2 in Figure 12).
Prior to making any measurements, calibrate the
with a known (that is, accurately measured) calibration
impedance connected between the VIN and VOUT pins of
the AD5933. The choice of calibration impedance topology
(for example, R1 in series with C1, R1 in parallel with C1)
depends on the application in question. However, ensure
that each component of the measured calibration impedance
is entered correctly into each chosen topology component
text box (see 2 in Figure 12). For this example, Resistor
2
AD5933 at
•
•
•
AD5933
Rev. 0 | Page 7 of 28
3
only R1 was chosen in the Calibration Impedance
section, that is, to measure the impedance of a 200 kΩ
resistive impedance across frequency. Also for this example,
set Resistor value R1 to 200E3 (Ω).
Click Program Device Registers (see 3 in Figure 12) to
program the sweep parameters as previously chosen into
the appropriate on-board registers of the
2
the I C interface.
The value programmed into the settling time cycles can be
further multiplied by a factor of 2 or a factor of 4 for a sweep.
Select ×1 (Default) in the DDS Settling Time Cycles section.
Now that the frequency sweep parameters and gain settings
are programmed, the next step is to calibrate the
system by calculating the gain factor.
The explanation of the system calibration gain factor, a term
calculated once at system calibration, is provided in detail
in the AD5933 data sheet. The
calibrated correctly for a particular impedance range before
any subsequent valid impedance measurement (refer to the
AD5933 data sheet for further details).
UG-364
4 5
AD5933 through
AD5933
AD5933 gain factor must be