Measurement Computing ZonicBook 618E rev.3.4 - Manual (Page 74)

Synopsis of Tach Modes
When you connect a tach sensor to a tachometer designated connector, such as the ZonicBook/618E’s
TACH BNCs (TACH1, TACH2, TACH3, or TACH4) 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
Use Counter Mode when Pulses per
Revolution are needed.
Counter Mode can be used for phase
shift observance.
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.
Period Mode
Use Period Mode when multiple
pulses are involved, such as from
gear teeth.
Period Mode cannot be used for
phase shift observance.
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.
Voltage Mode
Use Voltage Mode when you need to
determine a trigger voltage.
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.
7-10 Tach Channels 917695 ZonicBook/618E