SERIES AP220 / AP231 ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 28 -
http://www.acromag.com
- 28 -
https://www.acromag.com
4.2 Calibrated Performance
Accurate calibration of the AP231 or AP220 can be accomplished through
software control by using calibration coefficients to adjust the analog output
voltage. Unique calibration coefficients are stored in Flash memory as 1/16
LSB’s for each specific channel. Once retrieved, the channel's unique
offset
and gain coefficients can be used to correct the data value sent to the DAC
channel to accurately generate the desired output voltage.
The maximum calibrated error combining the linearity and adjusted offset
and gain errors:
AP231 Model
AD5761 @ -40oC to 85oC:
Linearity Error is +/-2 LSB
Offset Error is +/-0.0625 LSB
Gain Error is +/-0.0625 LSB
Total Error
+/-2.125 LSB (+/- 0.0032% FSR) maximum
AP220 Model
AD5721 @ -40oC to 85oC:
Linearity Error is +/-0.5 LSB
Offset Error is +/-0.0625 LSB
Gain Error is +/-0.0625 LSB
Total Error
+/-0.625 LSB (+/- 0.0152% FSR) maximum
Thus, correcting the value programmed to the DAC Channel Register using
the stored calibration coefficients provides the means to obtain excellent
accuracy.
Data is corrected using a couple of formulas. Equation (1) expresses the
ideal relationship between the value (
IdealCode
) written to the 16-bit DAC
to achieve a specified voltage within output range assuming Straight Binary
(also called Bipolar Offset Binary)
or 2’s Complement
data format (see Table
3.11 and 3.12).