VTI Instruments Ametek EX1200A Series, Руководство пользователя

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VTI Instruments Corp.
78 EX1200A Triggering
C
ONFIGURE THE
M
EASUREMENT
A simple DMM measurement can be configured by setting the function, range, and resolution.
There are many other parameters that may need to be configured depending on the type of
measurement being performed. This is explained in detail in later sections.

Function : Selects the measurement type (DCV, DCI, ACV, ACI, 2-wire resistance, 4-wire
resistance, temperature, frequency, or period).

Range : Selects the measurement range. The range should be set to the closest possible range
that is greater than or equal to the value passed as this parameter.

Resolution : Selects the measurement resolution. The fastest aperture time that will provide
this amount of resolution will be selected. If the amount of resolution is not possible, the
longest aperture will be selected.
IVI-COM Programming Interface
The VTEXDmmFunctionEnum interface provides properties and methods for selecting the
measurement function. The IVTEXDmm.Configure interface provides method for setting the
range and measurement function selection.
C
ONFIGURE
T
RIGGERING
The EX1200A DMM trigger model is divided into five states: IDLE, INITIATE, WAITING FOR
TRIGGER, WAITING FOR SAMPLE TRIGGER, and ACQUISITION (see Figure 4-3). A
system reset condition puts the EX1200A DMM in the IDLE state. The
DMM Initiate()
API call
begins the acquisition sequence by transitioning the instrument into the INITIATE layer. As this
occurs, the reading buffer memory is cleared.
As soon as the initiate process is complete, the device transitions to the TRIGGER state. The
DMM remains in the TRIGGER state until a specified TRIGGER event occurs. After receiving a
trigger, the DMM will wait the specified trigger delay until it takes a measurement. A delay allows
a signal to stabilize if needed. If a user-configured delay is used, it will override the automatic
trigger delay used by EX1200A DMM. Triggers can also be generated by software commands or
may be set to immediate, which causes a transition from the TRIGGER state to the
ACQUISITION state.
The SAMP TRIGGER acts as a secondary trigger. The same principles that apply to the
TRIGGER state apply to the SAMP TRIGGER state. Using the INTERVAL setting, the DMM
can be configured to take multipoint readings with a defined time interval.
NOTE The first measurement is taken when a Trigger event occurs (along with the corresponding delay)
and that the DMM will not wait for a Sample Trigger to occur per the IVI specification.
Each state has input values which can be set by the user:

Trigger Input Options
o
Trigger Input Source : sets the trigger line that moves the DMM from the Wait-For-
Trigger state to the Delay state.
o
Trigger Input Slope : indicates whether a rising or falling edge will move the DMM
from the Wait-For-Trigger state to the Delay state.
o
Trigger Input Count : sets the number of times the Wait-For-Trigger state will be
entered each time a measurement is initiated.
o
Trigger Delay : indicates the delay that occurs between when the trigger occurs and when
the measurement is actually taken. Valid values are 0 s to 4294.967295 s.
o
Auto-Delay : allows the DMM to automatically set the trigger delay based on the
measurement configuration.