Specifications

The tare calibration constants created during CAL:TARE are stored in and are
usable from the instrument’s RAM. To store the Tare constants in non-volatile flash
memory, execute the CAL:STORE TARE command.
NOTE The VT1419A’s flash memory has a finite lifetime of approximately ten thousand
write cycles (unlimited read cycles). While executing CAL:STOR once every day
would not exceed the lifetime of the flash memory for approximately 27 years, an
application that stored constants many times each day would unnecessarily shorten
the flash memory’s lifetime.
Resetting CAL:TARE To “undo” the CAL:TARE operation, execute CAL:TARE:RESet then
*CAL?/CAL:SET. If current Tare calibration constants have been stored in flash
memory, execute CAL:TARE:RESET, then CAL:STORE TARE.
Special
Considerations
Here are some things to keep in mind when using CAL:TARE.
Maximum Tare
Capability
The tare value that can be compensated for is dependent on the instrument range
and SCP channel gain settings. The following table lists these limits:
Maximum CAL:TARE Offsets
A/D range
± V F.Scale
Offset V
Gain x1
Offset V
Gain x8
Offset V
Gain x16
Offset V
Gain x64
16
4
1
0.25
0.0625
3.2213
0.82101
0.23061
0.07581
0.03792
0.40104
0.10101
0.02721
0.00786
0.00312
0.20009
0.05007
0.01317
0.00349
0.00112
0.04970
0.01220
0.00297
0.00055
N/A
Changing Gains or
Filters
To change a channel’s SCP setup after a CAL:TARE operation, a *CAL? operation
must be performed to generate new DAC constants and the “range floor” reset for
the stored Tare value. The tare capability of the range/gain setup that is to be used
must also be considered. For instance, if the actual offset present is 0.6 volts and
was “Tared” for a 4 volt range/Gain x1 setup, moving to a 1 volt range/Gain x1
setup will return Overload values for that channel since the 1 volt range is below
the range floor as set by CAL:TARE. See table on page 230 for more on values
returned for Overload readings.
Unexpected Channel
Offsets or Overloads
This can occur when the VT1419A’s flash memory contains CAL:TARE offset
constants that are no longer appropriate for its current application. Execute
CAL:TARE:RESET then *CAL? to reset the tare constants in RAM. Measure the
affected channels again. If the problems go away, reset the tare constants in flash
memory by executing CAL:STORE TARE.
Programming the VT1419A Multifunction
Plus
Compensating for System Offsets
Chapter 3 99
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