Fluke 8842a instruction manual Remote Erasure, Example Calibration Program

8842A

Instruction Manual

The C0 command can take up to 22 seconds. If during this time the controller continues to send the 8842A more commands, the commands may fill up the 8842A’s input buffer. If this happens, errors will probably occur.

You can avoid this problem by knowing when these commands are completed. There are three ways to determine this:

1.Monitoring the Cal Step Complete bit in the serial poll status register. This status bit is set false every time the remote processor sends a command to the in guard processor. It is then set true when the in guard processor completes the command and is ready to accept more. So you can send a command and loop on a check of the status, until the command is complete.

2.Setting the SRQ mask to generate an SRQ on Cal Step Complete. An SRQ is generated and the Cal Step Complete bit in the serial poll status response is set when a cal command is complete. This approach depends on capabilities of the controller being used.

3.Executing a delay in controller software after sending each command. (Not recommended.)

Although not usually necessary, these methods can be used for other commands as well.

6-25. REMOTE ERASURE

The C3 command allows you to erase the entire calibration memory. The erasure is executed by sending the string "C3 C0" (equivalent to pressing ERASE and then STORE). Any command other than C0 after C3 will abort the erasure. To facilitate remote calibration, the C0 command does not timeout as does the front panel ERASE button. The selective erasure that is possible from the front panel is intended as a troubleshooting aid, and is not available over the IEEE-488 Interface.

Note that the erase command can take up to 3 seconds to execute. To prevent timeout problems with the controller, you must determine when the command is completed before continuing. Several methods are presented in Timing Considerations, above.

NOTE

When erasing calibration memory, it is good practice to send the commands C3 and C0 in the same command string. Sending C3 by itself could lead to accidentally erasing calibration memory, since the C3 command does not time out as does the ERASE button.

6-26. EXAMPLE CALIBRATION PROGRAM

An example A/D calibration program is shown in Figure 6-5. The program is written in Fluke BASIC for the Fluke 1722A Instrument Controller. It uses the Fluke 5440A Direct Voltage Calibrator to perform and then verify the A/D Calibration procedure. In this program, the 8842A is at bus address 1, and the 5440A is at bus address 7.

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