Datasheet

UG-185 Evaluation Board User Guide
Rev. 0 | Page 6 of 16
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
as shown in . Figure 3
Program Voltage
The Program Voltage section programs the DAC register with
a value calculated from the three entered values: the positive
voltage reference (VREFP), the negative voltage reference
(VREFN), and the desired output voltage as shown in Figure 4.
0
9290-004
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. In the measurement example shown in
Figure 6, measurements are taken in 1024 code steps beginning
at Code 0 and finishing at Code 1,047,552, 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 1,048,576 measurement points takes ~21 hours to
complete.
09290-006
Figure 5. Saved Data Format
If an Agilent 3458A multimeter is not connected to the PC,
the software steps through the codes without taking any
measurements.