RTD Embedded Technologies, Inc.
|
www.rtd.com
55
DM35425HR User’s Manual
Use AIN0 and set it for a gain of 1 while calibrating the board. Connect your precision voltage source to AIN0. Set the voltage source to
+1.22070 mV, start a conversion, and read the resulting data. Adjust trimpot
TR6
until the data flickers between the values listed in the table
below.
Table 26: Data Values for Calibrating Bipolar 20 V Range
Offset (TR6)
Input Voltage = +1.22070 mV
ADC Converted Data
0000 0000 0000
0000 0000 0001
Unipolar Range Ideal Bit Weight
Below is a table listing the ideal input voltage for each bit weight for the unipolar ranges.
Table 27: ADC Bit Weights, Unipolar
Sign
ADC Bit Weight
Ideal Output Voltage (mV)
0 to +10 V
0
1111 1111 1111
+9997.60
0
1000 0000 0000
+5000.00
0
0100 0000 0000
+2500.00
0
0010 0000 0000
+1250.00
0
0001 0000 0000
+625.00
0
0000 1000 0000
+312.50
0
0000 0100 0000
+156.25
0
0000 0010 0000
+78.13
0
0000 0001 0000
+39.06
0
0000 0000 1000
+19.53
0
0000 0000 0100
+9.77
0
0000 0000 0010
+4.88
0
0000 0000 0001
+2.44
0
0000 0000 0000
0.00
7.2.3
G
AIN
A
DJUSTMENT
Should you find it necessary to check any of the programmable gain settings, the following table will show the proper trimpot to adjust.
Table 28: Trimpots for Calibrating ADC Gain
Gain
Trimpot
X2
TR7
X4
TR8
X8
TR9