EVALAD5933EB datasheet(12/32 Pages) AD

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EVAL-AD5933EB

Preliminary Technical Data

Rev. PrC | Page 12 of 32

The gain factor, which is calculated once at system calibration,

must be calibrated correctly for a particular impedance range

before any subsequent impedance measurement is valid (refer

to the AD5933 data sheet for a more detailed explanation of

gain factor).

The evaluation software can evaluate either a single midpoint

frequency gain factor or multipoint frequency gain factors (that

is, a gain factor for each point in the programmed sweep); see

Arrow 3. The midpoint gain factor is determined at the midpoint

of the programmed sweep; the multipoint gain factors are deter-

mined at each point in the programmed frequency sweep. After

you click Calculate Gain Factor, the software automatically

calculates the gain factor(s) for the subsequent sweep.

Once the midpoint gain factor or the multipoint gain factors

have been calculated, a message is returned to the main dialog

box of the evaluation software (see Figure 15). The gain factor(s)

returned to the evaluation software are subsequently used for

the sweep across the impedance being tested.

Figure 15. Confirmation of a Midpoint Gain Factor Calculation or a

Multipoint Gain Factors Calculation

After the system interface software calculates the gain factor(s)

for the programmed sweep parameters, this value appears in the

Calculated Gain Factor

section in the main dialog box of the

evaluation software.

However, it is important to note that if you change any of the

system gain settings (for example, if you change the output

excitation range, PGA gain, etc.) after the system has been

calibrated (that is, after the gain factor(s) have been calculated),

it is necessary to recalculate the gain factor(s) in order to sub-

sequently obtain accurate impedance measurement results. The

gain factor(s) calculated in software are not programmed into the

AD5933 RAM and are only valid when the evaluation software

program is open and running. The gain factor(s) are not retained

in the evaluation software after the software program is closed.

To begin the sweep, click Start Sweep (see Arrow 4). Once the

evaluation software completes the sweep, it automatically returns

both a plot of impedance vs. frequency and a plot of phase vs.

frequency for the impedance being tested (see Figure 14). The

progress of the sweep is outlined with a progress bar, as shown

in Figure 16.

Figure 16. Sweep Progress Bar (Blue)

To take a reading from the on-board temperature sensor, click

Measure

in the Internal Temperature box of the main dialog box.

This returns the 13-bit temperature of the device. See the AD5933

data sheet for more information on the temperature sensor.

To download the frequency sweep data (that is, frequency,

impedance, phase, real, imaginary, and magnitude data) from

the DFT of the sweep, click Download Impedance Data. The

common dialog box shown in Figure 17 now appears. Choose a

file name in the directory of choice and click Save (see Figure 17).

Note that the default is to save the file in a .csv format.

1: CHOOSE DIRECTORY

2: CHOOSE FILE NAME

3: SAVE THE FILE

Figure 17. Saving the Sweep Data

This saves the sweep data as a comma separated variable file

(.csv) located in the directory of your choice.

You can access this file content by using Notepad or Excel to

plot the data. Each file contains a single column of data. The

format of the downloaded data is shown in Figure 18

Figure 18. Opening the Sweep Data in Excel

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