American Magnetics 135 & 136 Liquid Helium Level Instruments (CE-Marked) - Manual (Page 64)

52 Rev. 3
Service Guide
Custom Instrument Configurations
6.2 Custom Instrument Configurations
6.2.1 Modifying the line voltage requirements
Warning
Before removing the cover of the instrument, remove the power from
the instrument by disconnecting the power cord from the power
receptacle. Failure to do this could expose the user to high voltages
and could result in life-threatening electrical shock.
Caution
The Model 135/136 instrument operates on 50-60 Hz power and
may be configured for 100-120 VAC or 200-240 VAC
±
10%. The
power requirements for each instrument are marked on the rear
panel. Be sure the instrument’s power requirements match your
power source prior to plugging in the line cord. Do not fail to connect
the input ground terminal securely to an external earth ground.
If the instrument operating voltage needs to be changed, ensure the
instrument is de-energized by disconnecting the power cord from the
power source. Remove the instrument cover and slide the voltage selector
switch on the main printed circuit board to the proper voltage. Replace the
instrument cover and indelibly mark the rear panel indications to match
the new configuration.
6.2.2 Enabling dirty sensor operational mode
Warning
Before removing the cover of the instrument, remove the power from
the instrument by disconnecting the power cord from the power
receptacle. Failure to do this could expose the user to high voltages
and could result in life-threatening electrical shock.
To operate in this mode, de-energize the instrument and remove the cover.
Place a jumper on W2 of the printed circuit board vertically-mounted
directly behind the front panel. Replace the cover and energize the
instrument. The operation in this mode is not detectable from the front
panel. Each time the sensor current is energized in the SAMPLE mode, a
high current is briefly shunted to the sensor before the actual level
measurement cycle is initiated.