Measurement Computing eZ-Record rev.2.1 - Manual (Page 18)

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eZ-Record Manual January 2001
Block Rejection Tab - Reject Panel
There are three block rejection modes: Double Hammer protects measurements
against double hammering: Overload protects the measurement by automatically
rejecting overloaded data, and Manual allows you to inspect a measurement and
optionally reject it for any reason. You can select any or all of the rejection
modes. (See also: Hints for Trigger Setup and Double Hammer Rejection)
Double Hammer: A double hammer occurs when a signal goes outside of the
acceptable range that is set up in the Hammer Rejection section. Click in the
Double Hammer box to turn the Double Hammer option ON and OFF. When
the box is checked, the option is ON.
Overload: An overload is any input signal that reaches or exceeds the specified
input Full Scale Voltage range. Click in the Overload box to turn the Overload
Rejection option ON and OFF. When the box is checked, the option is ON.
Manual: This option allows you to review each block of data before acquiring
the next block. When manual rejection is selected, a “Reject?” button is
activated in the main window. At the end of each average, if you want to
reject that measurement, click on the “Reject?” button. The analyzer will then
reject the current frame of data. The data and average counter will go back to
the previous measurement. Click in the Manual box to turn the Manual
option ON and OFF. When the box is checked, the option is ON.
Block Rejection Tab - Hammer Rejection Panel
In this panel you define the acceptable range for a hammer signal. Any signal
outside of this range is detected as a double hammer. The acceptable range looks
like the intersection of two roads. The signal must occur at the intersection.
X-axis Limits (% of blocksize): The x-axis Limits set the intersection at which
the impact must occur on the “road.”
Y-axis Limits (% of F(ull) S(cale): The y-axis Limits set the “road or lane
width” that extents across the x-axis.
Hints for Trigger Setup and Double Hammer Rejection
There are three major interrelated components to consider when setting up the
analyzer for double-hammer rejection.
1. Trigger Mode and Delay
2. Force Window
3. Double Hammer Region.
A trigger is used to ensure time synchronous measurements across all the active
channels. Pre-trigger states that the amount of data (specified by the delay) is
captured before a trigger event and prefixed to the data following the trigger
event. Post-trigger states that the amount of data (specified by the delay) is
discarded after the trigger event before capturing a block of data.
Double hammer reject is only meaningful with the pre-trigger specified. Double
hammer rejection protects the measurement from a bad hammering.
It is desirable to set the pre-trigger to fall within the hammer region, since it is a
common practice to set the trigger channel to an impact channel.