Measurement Computing DAC488 v.1 - Manual (Page 98)

92 Troubleshooting DAC488 User’s Manual
With the power cord plugged in and connected to the DAC488, turn on the unit by depressing the rear-panel
power switch. All of the front-panel LED indicators should light up for approximately one second while the
DAC488 performs an internal ROM and RAM self-check. At the end of this self-check all of the LED
indicators should turn off except for POWER.
Otherwise, the DAC488 may be in an error condition according to the one of the four following LED
patterns:
•
If all of the LED indicators remain on: Then a ROM error has occurred.
•
If the POWER LED indicator remains on while the rest of the LED indicators flash continuously:
Then a RAM error has occurred. Try cycling the power to the DAC488 to determine that the error is
repeatable.
•
If the POWER and ERROR LED indicator remain on while the rest of the LED indicators are off:
Then a checksum error on Non-Volatile RAM occurred, and the saved configurations may be lost. The
checksum error condition may be cleared by doing a save of a configuration using the System Defaults
(
S ) command. The error condition may also be cleared by using the Query Error Status ( E? )
command.
•
If all of the LED indicators are off: Then there may not be any power being supplied to the DAC488.
In this event, check to make sure that the AC power cable is securely connected at both ends.
Otherwise, there may be a problem with the fuse. For more information, see section Power Line &
Fuse Configuration in Chapter 3.
Trigger Processing & Trigger Overrun
Operation of the DAC488 is controlled by an internal 1 millisecond timer. Each DAC port is updated at a
maximum rate of once every millisecond. When a trigger event occurs, the DAC will output the
programmed voltage within 1 millisecond of receiving the trigger. If a second trigger event occurs before
the DAC has finished processing the first trigger, the second trigger will be held pending and a trigger
overrun error will occur. The error condition may be cleared by issuing the Error Query command (E?) and
then reading the response from the DAC488. After the first trigger is processed, the pending trigger will
then be processed. Any additional triggers which may occur while a trigger is held pending will be ignored.
Query Error Status
The Query Error Status ( E? ) command is used to determine the present error condition on the selected port
of the DAC488. After execution of the Query Error Status command, the present error condition is cleared.
The error condition is also cleared by executing the Status (
U0 ) command. When an error has occurred, the
ERROR LED on the DAC488 front panel will turn on. The ERROR LED will stay on until a Query Error
Status (
E? ) or Status ( U0 ) command is executed.
If a Calibration Write Protected Failure ( E4 ) occurs, this error condition may also be cleared by executing
the Query Error Status ( E? ) command. This type of error occurs when an attempt is made to save
Calibration Constants without first setting the calibration switch on the back panel to the depressed position.
If a Non-Volatile RAM error ( E5 ) occurs on power up, the S? command may be used to check the system
defaults. One of the following responses will be returned:
•
S0 = Factory defaults are in use, user programmed defaults were lost
•
S1 = User programmed defaults are still valid
The Calibration Constants may be tested by issuing the following command string: A0 R0 X J? . One of
the responses below will be returned:
•
J128,128 = Factory Calibration Constants are in use, Calibration Constants which were saved from a
calibration procedure have been lost. The DAC488 should be recalibrated if this response is returned.
•
J127,127 = Calibration Constants which were saved from a calibration procedure are still valid.
For more information, see the Query Error Status ( E? ) command in the Chapter 7 command reference.