42 Rev. 2
Calibration
Open dewar calibration
calibration so that it can be used immediately by the customer. However,
the customer is still expected to perform a more accurate calibration where
feasible, such as the open dewar or closed dewar calibration, with the
target liquid.
For the case where a sensor is too long to be calibrated in AMI facilities,
AMI will perform a partial length open dewar calibration in liquid
nitrogen, and then calculate the MAX calibration point. A dielectric ratio
may also be subsequently utilized to adjust for a target liquid other than
liquid nitrogen. The customer is expected to perform a more accurate open
dewar or closed dewar calibration if feasible.
As a quick guide for selection of the best calibration method available, a
calibration selection diagram is presented below. If the instrument and
sensor are purchased as a unit from AMI, then the factory calibration will
be adequate in most cases. However, for the exceptions noted in the
previous paragraphs (which are approximate calibrations), the customer
should perform a more accurate open dewar or closed dewar calibration. A
customer performed calibration is also required for sensors that are
purchased as a separate item from the instrument, since the instrument
and sensor were not both available for calibration at AMI facilities.
Each Model 1700 Instrument must be calibrated with a sensor before use.
If the instrument was purchased with a sensor to be used in liquid
nitrogen, the instrument has been calibrated at the factory.
4.2.4.1 Selection of Capacitance Sensor Calibration Methods
As a quick guide for selection of the best calibration method available, a
calibration selection diagram is presented in 4-7. If the instrument and
sensor are purchased as a unit from AMI, then the factory calibration,
including sensor serial number and sensor physical parameter information
entered at the factory, will be adequate in most cases. However, for the
exceptions noted in the following paragraphs (which are approximate
calibrations), the customer should perform a more accurate open dewar or
closed dewar calibration if at all possible. A customer-performed
calibration is also required for sensors that are purchased as a separate
item from the instrument, since the instrument and sensor were not both
available for calibration at AMI facilities.
The most straightforward calibration method is the Open Dewar
Calibration which requires the customer to have access to a filled dewar
where the full active length of the sensor can be dipped. The Closed Dewar
Calibration method can be performed in situations where it is not feasible
for the customer to dip the sensor into an open dewar, such as situations
where the target liquid is under pressure. The closed dewar calibration is
more complex and requires initial preparations to insure success.
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