Measurement Computing Data Translation DT9857, User Manual

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Calibration
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6. Repeat steps 3 to 5 for each analog input channel on the module.
Note: At any time, you can click Restore Factory Settings to reset the A/D calibration
values to their original factory settings. This process will undo any auto or manual calibration
settings.
Using the Manual Calibration Procedure
If you want to manually calibrate the analog input circuitry instead of auto-calibrating it, do
the following for each channel:
1. Select the A/D Calibration tab of the calibration utility.
2. Under the Calibration Settings area of the window, select the sampling frequency, in
Hertz, and the gain that you want to use.
Notes: The DT9857 and DT9857E modules have two power modes: low power mode and
high power mode. Low power mode is calibrated when you specify a sampling frequency
less than 52.734 kHz. High power mode is calibrated when you specify a sampling
frequency greater than 52.734 kHz. Ensure that you calibrate the board for both high and
low power mode if you are using sampling frequencies below and above 52.734 kHz.
By default, this utility uses DC coupling with the current source disabled. This is the
recommended setting for most users. While changing these settings is not advised for
most users, users with unique applications can change these settings by clicking the
Advanced button.
3. Under the Manual Calibration area of the window, select the channel that you want to
calibrate, and then click the
Start button.
4. Adjust the offset as follows:
a. Verify that 0.0000 V is applied to the channel that you want to calibrate.
The current voltage reading for this channel is displayed in the AD Value box.
b. Adjust the offset by entering values between 0 and 255 in the Offset edit box, or by
clicking the up/down buttons until the AD Value is 0.0000 V.
5. Adjust the gain as follows:
a. Verify that +9.3750 V is applied to the channel that you want to calibrate.
The current voltage reading for this channel is displayed in the AD Value box.
b. Adjust the gain by entering values between 0 and 255 in the Gain edit box, or by
clicking the up/down buttons until the AD Value is 9.3750 V.
6. When you have finished calibrating the channel, click the Stop button.
7. Repeat steps 3 to 6 for each analog input channel on the module.