Sensoray 618 - Manual (Page 16)

Sensoray Model 618/619 Smart A/D 14 Programming
Typically, this function is invoked just before a call to
SetGageSpan. Together, the SetGageZero and
SetGageSpan functions serve to completely calibrate a
gage channel.
5.6.2 SetGageSpan
Declares a known load condition for a strain/pressure
gage channel, and the numerical load value expected
from the Smart A/D board when measuring the current
load.
This function is used in conjunction with the
SetGageZero function to prepare a sensor channel for
gage measurements. Invoke this function after declaring
the sensor type, but before acquiring sensor data from a
channel.
The SetGageSpan function requires that a precisely
known load, called the “calibration load,” be applied to
the target sensor. In some cases the calibration load can
be simulated by using an internal, precision calibration
resistor—present in many gages—to unbalance the
sensor bridge. In the case of gages that do not provide a
calibration resistor, a mechanical load must be applied to
the sensor.
Ideally, the calibration load will be close to the actual
load values to be measured. If a wide range of load
values are to be measured, it is best to employ a
calibration load that is equal to or larger than the largest
application load to be measured.
Before invoking this command, you must apply either a
simulated or true mechanical zero load condition to the
sensor and invoke the SetGageZero command, as
described in Section 5.6.1. This must be done before
(preferably immediately before) executing the
SetGageSpan function.
5.6.3 SetGageTare
Tares the strain/pressure gage connected to the specified
channel. This function is used to compensate application
load offsets.
For example, an empty container is often used to hold a
material that is to be weighed. Since the container itself
is not to be measured, the SetGageTare function can be
invoked with a load consisting of only the empty
container. After executing this function, the Smart A/D
board will subtract off the container load and return only
the load value of the container contents.
Before invoking this command, the gage channel should
be calibrated. See Section 5.6.1, Section 5.6.2 and
Section 5.6.5 for details.
5.6.4 GetGageCal
Returns the gage calibration parameters from the sensor
channel specified by ChannelNumber. The
*GageCal
argument is a pointer to an application buffer
which is to receive the calibration parameters.
This function makes it possible to restore a channel’s
gage calibration without using the SetGageZero or
SetGageSpan functions. The returned parameters may be
saved by the application and used to later restore a gage
calibration by means of the SetGageCal function.
The returned parameters are useful only if the gage has
already been calibrated. This prior calibration may have
been accomplished in either of two ways:
• Using SetGageZero and SetGageSpan functions. This
method must be used if the sensor channel has never
been calibrated for the gage to which it is connected.
• Using the SetGageCal function.
5.6.5 SetGageCal
This command restores a channel’s strain/pressure gage
calibration settings by using calibration parameters that
were obtained from the GetGageCal function.
The *GageCal argument is a pointer to an application
buffer which contains the gage calibration parameters.
Arguments: ChannelNumber
LoadValue
Returns: void
Arguments: ChannelNumber
Returns: void
Arguments: ChannelNumber
*GageCal
Returns: void
Arguments: ChannelNumber
*GageCal
Returns: void