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HYDRA
Service Manual
4-18
4-19. External Trigger Input Test
The External Trigger Input Test verifies that the rear panel trigger input of Hydra is
functioning properly.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the eight-terminal Alarm Output connector from the rear of Hydra and all
external connections to it. Connect short wires (to be used as test leads) to the Gand
TR terminals. Leave other ends of wires unconnected at this time. Reinstall the
connector. Refer to Figure 4-4.
3. Switch power ON.
4. On Hydra, select the VDC function, 30V range for channels 0 through 5. Select a
scan interval of 30 seconds.
5. Select trigger ON to enable the external trigger input. Press SHIFT, then
MON(TRIGS). (The display shows TRIG.) Then press either the up or down arrow
buttons until the display shows ON. Finally, press ENTER.
6. Press the Hydra SCAN button. Hydra should scan channels 0 through 5 once every
30 seconds.
7. During the interval when scanning is not occurring, connect (short) the test leads of
the TR and ground Alarm Output terminals.
Ensure the connection causes a single scan to occur.
8. Disconnect (open) the TR and ground connection.
Ensure the scan continues to execute at its specified interval.
+–0123TR 01234567
Σ
9-16 V
DC PWR
!
+30V
ALARM OUTPUTS DIGITAL I/O
+–0123TR
s29f.eps
Figure 4-4. External Trigger Test
4-20. Calibration
Hydra calibration is controlled with computer interface commands. The 2620A may be
calibrated by using the IEEE-488 or RS-232 interface, but the 2625A and 2635A may
only be calibrated via their RS-232 interface. Local (front panel) calibration is not
possible.