Data Translation DT9824, User Manual, Page: 72 / 102

Chapter 7
72
Using the Manual Calibration Procedure
Note: Ensure that you let the DT9824 module warm-up for a minimum of 1 hour before
calibrating it.
If you want to manually calibrate the analog input circuitry instead of auto-calibrating it,
perform the following steps:
1. Select the A/D channel to calibrate (at the top of the window).
2. Select the frequency to use for the calibration (100 or 1200). If you select 100, the chopper
is enabled for the A/D converter at frequencies equal to or lower than 960 Hz. If you
select 1200, the chopper is disabled for the A/D converter at frequencies greater than
960 Hz.
3. Adjust the offset for the selected channel as follows:
a. Select the gain to apply to the channel (1, 8, 16, or 32).
b. To calibrate to 0 V, connect a dead-short wire to the selected channel.
The actual voltage is continuously returned in the AD Voltage text box. Since this number is
constantly changing, a Running Average value is also displayed.
c. If desired, click the Reset button under the Running Average edit box to reset the
running average.
d. Once the Running Average value has settled, adjust the offset by entering values in
the Offset edit box, or by clicking the up/down buttons until the Running Average
value matches 0 V.
e. Repeat steps 3a to 3d, selecting the next gain in the list, until the offset values are
calibrated for each gain setting.
4. Adjust the gain for the selected channel as follows:
a. Select the gain to apply to the channel (1, 8, 16, or 32).
b. Apply the appropriate voltage, shown in Table 20 , for the selected gain .
c. If desired, click the Reset button under the Running Average edit box to reset the
Running Average value.
Table 20: Voltages for Calibrating the Gain
Gain Voltage to Apply
1 9.60000 V
8 1.20000 V
16 0.60000 V
32 0.30000V