Procedure for oscilloscope monitoring of DCH low voltage power supply
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		       Last updated:  13 October 2005


The BaBar drift chamber low-voltage power supply (LVPS) is located in the
BaBar electronics house in Rack 12.  The supply puts out up to 300A at 8V
(adjustable) and constitutes an electrical stored energy hazard for burns.

This procedure allows a user to apply scope probes to the power supply
output terminals and to monitor the performance of the supply in operation.
The user must be trained in lockout/tagout (LOTO) procedures.

1. Turn off power.

	HAZARDS:  Electrical shock, burn.

	a)  Turn off LVPS front-panel switch.
	b)  Turn off breaker supplying power to LVPS.
	c)  Apply LOTO lock and tag to breaker switch.

2. Attach oscilloscope probe to the positive output of the supply.
3. Attach the probe ground to the negative output of the supply.

	HAZARDS:  Minor cuts, abrasions.

	a)  Output terminals accessible on back of LVPS.
	b)  Exercise due caution in tight quarters.

	HAZARDS:  Electrical shock, shorts, fire.

	c)  Ensure that probes are in good condition, properly insulated,
	    and isolated from each other and from LVPS chassis.

4. Measure LVPS output response with oscilloscope.

	HAZARDS:  Electrical shock, shorts, burns.

	a)  Close rack rear door, restrict access to power supply terminals.
	b)  Remove LOTO lock and tag from breaker switch and turn on.
	c)  Turn power supply on and off, capturing output with scope.
	d)  Repeat (c) as necessary, configuring scope appropriately.

5. Disconnect oscilloscope, restore normal LVPS operation.

	HAZARDS:  Electrical shock, shorts, burns.

	a)  Turn off LVPS front-panel switch.
	b)  Turn off breaker supplying power to LVPS.
	c)  Apply LOTO lock and tag to breaker switch.

	HAZARDS:  Minor cuts, abrasions.

	a)  Exercise due caution in tight quarters.
	b)  Remove oscilloscope probes from LVPS terminals.
	c)  Remove LOTO lock and tag from breaker switch and turn on.
	d)  Turn on LVPS front-panel switch.

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