American Magnetics 135 & 136 Liquid Helium Level Instruments (CE-Marked) - Manual (Page 47)

Rev. 3 35
Remote Interface Reference
IEEE-488 Command Set Reference
4.2.4.5 Commands for performing level measurements
The LEVEL command returns the liquid helium level in the current units
selected. If a measurement is in progress when the instrument is queried
for the LEVEL, then the LEVEL command (and in fact, all commands) will
not return a value until the measurement is complete. The time required
to complete a level measurement is variable and depends upon the active
length of the sensor and the sampling mode. Measurement times normally
range from several milliseconds to 15 seconds. Sampling in the UPDATE
mode usually returns immediately since the resistive zone of the sensor is
kept in continuous contact with the surface of the liquid helium. The
return value (and termination characters) from the LEVEL command
must be received before sending another command to the Model 135/136.
The HOLD command ceases level measurements regardless of the
sampling mode selected. A new measurement will not be initiated until the
MEASURE command is subsequently received. The MEASURE command
resumes level measurement in the sampling mode as set by the sampling
mode toggle switch on the front panel.
Note
The MEASURE command resumes measurement of the liquid
helium level in the mode determined by the sampling mode toggle
switch on the front panel. If the sampling mode toggle switch is in
the UPDATE position, the sensor current will turn on and the
instrument will continually update. If the switch is in the SAMPLE
position, the sensor current will briefly turn on to allow the
instrument to perform and immediate measurement, then turn off.
The instrument will then remain in the SAMPLE mode with the
interval and start time of the sampling function undisturbed.
Command: LEVEL Function: Returns the liquid
helium level in the
current units
Returns: <value>
Command: HOLD Function: Immediately ceases
level measurements
Returns: HOLD
Command: MEASURE Function: Initiates level
measurement in the
current sampling
mode
Returns: MEASURE