4
August 18, 2003
V.
MAINTENANCE
A.
The instrument was shipped with a full charge on the batteries. Operating under a
maximum power consumption of measuring a 60" sensor in a near empty dewar, the unit
is capable of making approximately 1,000 level measurements before battery recharging
is required.
B.
The failure of the front panel LED to light when a measurement is being made indicates
low battery power. If the front panel LED fails to stay lit during a measurement, the
batteries should be recharged. The supplied AC adapter plugs into a 90VAC to 132VAC
50/60Hz (or optional 180VAC to 264VAC 50/60Hz for the European model) source and
into the jack provided on the side of the instrument. The batteries should be charged for
a minimum of 1 hour before taking more readings; subsequently, as soon as it is feasible,
batteries should be charged for at least 72 hours to fully charge the battery.
NOTE: Best battery performance will be realized by charging
the Model 150A continuously whenever it is not being used.
NOTE: The AC adapter is rated for connection to Category II
mains voltages.
NOTE: Only AMI approved AC adapters should be used on the
device.
NOTE: Only an authorized service representative should replace
the factory installed batteries.
C.
As part of the routine maintenance, keep the exterior surfaces of the instrument clean by
gently wiping with a damp cloth moistened with a mild detergent.
VI.
CALIBRATION
The instrument is calibrated for a specific sensor length before shipping and should never
need adjustment. However, the calibration procedure is included for your information.
All AMI sensors have a resistance of 4.56 ohms/cm (active length) when in the normal
state and maintained just above the transition temperature of 10K. Thus, if you are using
a 50 cm sensor, you will need a 50 x 4.56 = 228.0 ohm resistor for calibration purposes
(ensure that the resistor power rating is sufficient and that its temperature coefficient is
adequately low such that self-heating due to the 75 mA excitation current does not cause
excessive shift in the resistor’s resistance).
NOTE: The active length of a sensor is usually 1" less than its
overall length.
NOTE: Disconnect the helium level sensor from the instrument.
