VTI Instruments Ametek EX1200A Series, User Manual

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VTI Instruments Corp.
84 EX1200A Triggering
Auto Zero Off
The auto-zero function can be disabled programmatically to achieve higher measurement speeds.
Once the auto-zero is disabled, the DMM no longer takes the new zero and reference
measurements, but, instead, uses the last known zero and reference values to calculate the signal
level. VTI recommends, however, that auto-zero be performed as frequent as possible, especially
when the ambient temperature fluctuates significantly.
Auto Zero Once
This option enables auto-zero for the first measurement and then disables auto-zero for all
subsequent measurements. Even after disabling the auto-zero, the last measured zero and reference
readings are used for all successive measurements.
L
IMITS
It is possible to perform lower and upper limit check functions after every measurement. The
DMM validates the measured reading against these limits and provides a trigger interrupt when
the reading is outside of the limit requirements. The limits can be set to any value between 0% and
±120% of the highest range for the present function. The upper limit should always be larger than
the lower limit. The interrupt can be routed to be any valid LXI trigger output, including the
general purpose DIO lines available at the rear panel. In this way, a limit violation can act as a
‘trigger source’
and initiate an appropriate action. For example, a measurement channel can be
configured to validate an upper and lower voltage limit and trigger an alarm when any deviations
are found. These functions are volatile, however, and must be programmed in the same manner
whenever power is cycled or upon reset.
The default value for both upper and lower limit is ±infinity.
M
ATH
F
UNCTIONS
The EX1200A DMM allows the user to define gain and offset readings for each measurement. By
doing so, the user can define custom conversion factors (i.e. define custom transducers). As with
limits, the math functions are volatile and must be reasserted upon power cycle/reset.
These gain and correction factors are applied after calibration constants and auto-zero calculations
are performed but before limits are evaluated. Using this methodology, a custom linearization
formula (Y = mX+c) can be defined for every measurement. Note that the gain and offset factors
apply to all functions (dc and ac volts, dc and ac current, 2- and 4-wire resistance, frequency, and
period)
except for temperature.
The default value for gain and offset are
“1”
and
“0”,
respectively.