Datasheet

Evaluation Board User Guide UG-257
Rev. 0 | Page 5 of 20
USING THE AD7195 EVALUATION BOARD IN STANDALONE MODE
The AD7195 evaluation board can be operated in standalone
mode. In this mode, the evaluation board functions as a dc
excited weigh scale demonstration. Channel AIN3-AIN4 is
the analog input channel. The AIN3 and AIN4 pins along
wit h AV
DD
and AGND are connected to the J4 header. This
header allows the user to connect a load cell to the AD7195.
The load cell should be connected to the header as shown in
Figure 5. A 6-wire load cell is shown, but a 4-wire load cell can
also be connected. The three reference links on Header J3
must be removed (see Figure 6).
EXC+
EXC–
OUT–
OUT+
SENSE+
SENSE–
09727-005
AGND
EXC+
REF(+)
AIN3(+)
AIN4(–)
REF1–
BPDSW
EXC–
J4
Figure 5. Load Cell Connection to Header J4
AV
DD
AIN1 AIN2 AINCOM AGND REF– REF+ VREF
J3
09727-006
Figure 6. Link Positions for Standalone Mode
The AD7195 is configured for an update rate of 4.69 Hz, and
the gain is programmed to 128. Channel AIN3-AIN4 is selected
as the active channel.
The conversions from the AD7195 are displayed on the LCD
display. The four buttons beneath the LCD display allow the
user to calibrate the weigh scale system, adjust the LCD
contrast, and read the offset and gain registers. The function
of each button is listed at the bottom of the LCD display.
To operate the weigh scale demonstration, connect the load cell
to Header J4 as shown in Figure 5. Apply power to the AD7195
evaluation board using either a 9 V battery or a 9 V dc power
source. Ensure that Link J1 is in Position 5 V BAT/EXT. The
weigh scale demonstration can also be powered from the USB
connector if the board is connected to a PC. Link J1 should be
in Position 5 V USB in this case.
With no weight on the weigh scale, perform an offset
calibration. Then, place the expected full-scale weight on the
load cell, and perform the full-scale calibration. Next, select the
corresponding full-scale weight on the LCD display as the
weigh scale demonstration supports full scale weights of 500 g
to 10 kg. The software then continuously reads conversions
from the AD7195, scales the conversions appropriately, and
displays the resulting weight on the LCD display.