Main Window - Analog Devices EVAL-AD5781 User Manual

UG-184

MAIN WINDOW

The main window is divided into three tabs: Configure,
Program Voltage, and Measure DAC Output.
Configure
The Configure section allows access to the control register,
clearcode register, software control register, and DAC register
and also allows control of the RESET , CLR , and LDAC pins.
Program Voltage
The Program Voltage section programs the DAC register with
a value calculated from the entered values: the positive voltage
reference (VREFP), the negative voltage reference (VREFN),
and the desired output voltage (see Figure 4).
Figure 4. Program Voltage Window
Measure DAC Output
The Measure DAC Output section allows the PC to control an
Agilent 3458A multimeter to measure and log the DAC output
voltage.
The multimeter is controlled over a general-purpose interface
bus (GPIB). Once connected to the PC, the multimeter should
first be configured via its front panel before taking a measure-
ment. Figure 6 shows the measurement options. The software
runs through a sequence of steps, programming the DAC
register and measuring the DAC output voltage. The sequence
begins with the software programming the DAC with the Start
Code value, incrementing the programmed value at each step
by the Code Step value, and finishing when the programmed
value reaches the Stop Code value. A delay between measure-
ments can be inserted if required. The GPIB address of the
multimeter must be specified.
To begin the measurement, click the START button. The
measurement can be halted at anytime by clicking the STOP
button. When the measurement is completed, a dialog box
appears to allow the data to be saved as a spreadsheet file
with three columns of data. The first column is DAC code,
the second column is DAC voltage in volts, and the third
column is INL error in LSBs, as shown in Figure 5. A graph
of both DAC output voltage vs. DAC code and INL error vs.
DAC code is displayed on-screen (see Figure 6). In the
measurement example shown in Figure 6 measurements are
taken in 256 code steps beginning at Code 0 and finishing
at Code 261,888, in total 1023 measurements. With the number
of power line cycles (NPLC) setting on the multimeter set to 1,
the measurement takes ~75 sec to complete. To complete an all
codes measurement requiring 262,144 measurement points
takes ~6 hours to complete.
If an Agilent 3458A multimeter is not connected to the PC,
the software steps through the codes without taking any
measurements.
Rev. 0 | Page 6 of 16
Evaluation Board User Guide
Figure 5. Saved Data Format