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With the stage 0 attenuator compensation aligned, the front end x10 attenuators can be

aligned. To separate the action of each and because the available test signals are likely to be

limited to a few volts, these attenuators will have to be adjusted one at a time. This is a departure

from normal instrument operation. Click the Ok button to clear the message for stage 0. A

similar message will appear for stage 1. Apply a signal with an amplitude in the range of a few

volts and use the same method as above to adjust the compensation trimmer for stage 1. Click

Ok again to repeat for stage 2 with the same input signal. Click Ok a final time and the

instrument will return to its original settings.

This completes the attenuator compensation calibration. Repeat this procedure for each

channel until the performance is satisfactory. It will be helpful to examine performance on rising

and falling edges over a range of input signal frequencies and instrument settings

4.1.2 Stored Calibration Controls

Other than analog compensation, all calibration information is stored in non-volatile

memory in the instrument hardware. This information is retrieved and applied by the software

when the application is started. This operation occurs at the level of the API library so it will

be transparent to any top level application which uses the API.

As calibration items are adjusted, they are adjusted only within the API and not saved

back to the instrument. The button Load Calibration is available to load the information from

the instrument as it was before calibration began. The button Save Calibration is will save the

calibration information in the API, as adjusted by any updates, to the instrument non-volatile

memory. The button Clear Calibration will return all gains and offsets to nominal values and

clear the non-volatile memory on the instrument. This step is rather drastic, and calibration can

usually be completed without the need to do this. Calibration will be a quicker process if it is not

cleared, because the user can take advantage of previous calibration settings which are likely

close to where they need to be. If significant repairs have been made to a damaged instrument

it may help to clear the calibration memory.

The serial number of the instrument is also stored in non-volatile memory. The button

Set Serial Number allows this number to be changed to the displayed value in the edit box. The

serial number on the product labeling will always be the official serial number of the unit for

purposes of communicating with Data Design regarding the module. The number stored in the

instrument electronics allows the user to easily identify the unit in use. For this reason it is

recommended that this number never be changed. But then in the spirit of open source, the user

is provided with the ability to do bad things as well as good things.

DDC TR122 User Manual

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