Measurement Computing eZ-Analyst rev.14.1 - Manual (Page 57)

eZ-Analyst 978791 Edit Menu 4-21
Synopsis of Tach Modes
When you connect a tach sensor to a tachometer designated connector, such as the
ZonicBook/618E’s TACH BNCs (T1, T2, T3, or T4) you can select one of the following three
modes: Counter, Period, or Voltage. If you connect a tachometer sensor to a direct Analog
Signal Input channel (CH1 through CH8) then the tachometer signal will only be accepted in
the Voltage Mode.
If tachometer triggers will occur at a rate greater than or equal to the
“scan rate divided by 10” then the Period Mode must be used.
Counter Mode
Counter Mode generates a Pulse of Amplitude “+1” for
each tach trigger. The counter mode can be used when
the number of pulses is less than the scan rate divided
by ten (< scan rate / 10).
Once you have established the phase relationship of a
machine running near optimum, the observance of phase
shifts can be used to signal the development of a
mechanical problem.
Use Counter Mode when Pulses per
Revolution are needed.
Counter Mode can be used for phase
shift observance.
Period Mode
The period is the time from the rising edge of one pulse
to the rising edge of the next pulse, or the time from the
falling edge of one pulse to the falling edge of the next
pulse.
The Period Mode is used for Tachometer inputs which
exhibit multiple pulses per revolution. The mode
provides accurate overall RPM without sacrificing scan
rate. Phase measurements are not possible when using
period mode.
Note: 60 seconds divided by the period [in seconds]
equals RPM.
Use Period Mode when multiple
pulses are involved, such as from
gear teeth.
Period Mode cannot be used for
phase shift observance.
Voltage Mode
Voltage Mode is used for Tachometer inputs to view
actual input voltages from the Tach Sensor. Voltage
mode is useful for locating an ideal Tach Trigger Voltage
setting. An ideal trigger voltage is one that is in a clean
region of a leading edge. Note that Voltage Mode cannot
be used for Phase measurements between Analog Inputs
and Tachometer Inputs.
If you connect a tachometer sensor to one of the 8
Analog Signal Input channels (CH1 through CH8) instead
of a TACH channel, then the tachometer signal will only
be accepted in the Voltage Mode.
Use Voltage Mode when you need to
determine a trigger voltage.