American Magnetics 135 & 136 Liquid Helium Level Instruments (CE-Marked) - Manual (Page 31)

Rev. 3 19
Operation
Normal Operational Mode
3.2.6 Configure the sample time interval setting
To adjust the sample time interval, place the control mode rotary switch in
the INTERVAL position. Use the RAISE/LOWER toggle switch to adjust
the time interval in the same manner as described in paragraph 3.2.2. The
instrument is shipped with the time interval set for 1.0 minutes. This
value can be changed to any setting between 0 and 600 minutes.
Warning
Before removing the cover of the instrument, remove 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.
If desired, the sample interval can be changed to hours. To accomplish
this, the unit must be de-energized and the cover removed so that jumper
W1 (located on the printed circuit board vertically mounted directly behind
the front panel) can be moved from MIN to HR position. The jumper
position can be determined from the front panel at any time. When the
jumper is in the hour position, the display will briefly flash ‘hhh.h’ when
the RAISE/LOWER switch is moved out of the center position (with the
control mode rotary switch in the INTERVAL position) and then will
display the time to tenths of an hour. When the jumper is in the minute
position, the display does not flash ‘hhh.h’.
3.2.7 Select either continuous or sampled update configuration
Place the sampling mode toggle switch in the UPDATE position for
continuous level readings, or in the SAMPLE position for readings taken
at time intervals according the INTERVAL setting. All sample time
intervals are initialized from the time the instrument was last powered on.
If the sampling mode toggle switch is the UPDATE position, the resistive
zone of the sensor is kept in continuous contact with the surface of the
liquid helium. This results in heating effects and an accelerated loss of
liquid helium. The SAMPLE position allows the unit to perform a
measurement and then de-energize the sensor, thereby minimizing the
heating effects and loss of liquid helium.
3.2.8 Select the appropriate units display option
Place the units mode toggle switch in the position desired for the display
output units. The % position displays the percentage of active sensor
length that is immersed in liquid helium.
3.2.9 Connect the optional analog output signal
If the instrument was purchased with an analog output option, the
auxiliary connector J2 on the rear of the instrument provides a 0-10 VDC