Omron H7CX Series Manual page 24

H7CX (Tachometer Function)
Explanation of Functions
3.3,
Tachometer Output Mode (
switch.)
Set the output method for control output based on the OUT1/
OUT2 set value. Upper and lower limit (HI-LO), area (AREA),
upper limit (HI-HI), and lower limit (LO-LO) can be set. (For details
on the operation of the output modes, refer to Output Mode Set-
tings on page 30.)
"-32
Counting Speed ( ) (Setting possible using DIP switch.)
Set the maximum counting speed (30 Hz/10 kHz) for CP1 input. If
contacts are used for input signals, set the counting speed to
30 Hz. Processing to eliminate chattering is performed for this
setting.
#/
Decimal Point Position ( )
Decide the decimal point position for the measurement value,
OUT1 set value, and OUT2 set value.
/2"+
Prescale Value ( )
It is possible to display the rate of rotation or the speed of a device
or machine to which the H7CX is mounted by converting input
pulses to a desired unit. If this prescaling function is not used, the
input frequency (Hz) will be displayed.
The relationship between display and input is determined by the
following equation. Set the prescale value according to the unit to
be displayed.
™
Displayed value = f a
f: Input pulse frequency (number of pulses in 1 second)
a: Prescale value
1. Displaying Rotation Rate
Display unit
rpm
rps
N: Number of pulses per revolution
Example:In order to display the rate of rotation for a machine that
outputs 5 pulses per revolution in the form @@.@ rpm:
1. Set the decimal point position to 1 decimal place.
2. Using the formula, set the prescale value to 1/N
= 60/5 = 12.
2. Displaying Speed
Display unit
m/min
m/s
N: Number of pulses per revolution
d: Diameter of rotating body (m)
p
d: Circumference (m)
4&
Average Processing ( ) (Setting possible using DIP
switch.)
Flickering display and output chattering can be prevented using
average processing (simple averaging). Average processing can
be set to one of four levels: no average processing, 2 times (i.e.,
the average of 2 measurement values), 4 times, or 8 times. The
measurement cycle will be equal to the sampling cycle (200 ms)
multiplied by the average processing setting (i.e., the number of
) (Setting possible using DIP
Prescale value (a)
™
1/N 60
1/N
™
60
Prescale value (a)
p ™ ™
d 1/N 60
p ™
d 1/N
d: Diameter of
rotating body
H7CX (Tachometer Function)
times). Average processing enables fluctuating input signals to be
displayed stably. Set the optimum number of times for the applica-
tion.
43
Auto-zero Time ( )
It is possible to set the H7CX so that if there is no pulse for a cer-
tain time the frequency is measured as 0. This time is called the
auto-zero time. Set the auto-zero time to a time slightly longer
than the estimated interval between input pulses and within the
setting range (0.1 to 99.9 s). It will not be possible to make accu-
rate measurements if the auto-zero time is set to a time shorter
than the input pulse cycle. Setting a time that is too long may also
result in problems, such as a time-lag between rotation stopping
and the alarm turning ON.
23,1
Startup Time ( )
In order to prevent undesired output resulting from unstable input
immediately after the power supply is turned ON, it is possible to
prohibit measurement for a set time (0.0 to 99.9 s), the startup
time. It can also be used to stop measurement and disable output
until the rotating body reaches the normal rate of rotation, after
the power supply to the H7CX and rotating body are turned ON at
the same time.
Display
Startup time
Comparison
value
(lower limit)
Power supply
Output
(lower limit)
(,.#
NPN/PNP Input Mode ( )
Select either NPN input (no-voltage input) or PNP input (voltage
input) as the input format. The same setting is used for all exter-
nal inputs. For details on input connections, refer to The circuit
shown above is for no-voltage input (NPN input). on page 36.
".+1
Display Color ( )
Set the color used for the measurement value.
Setting Control output OFF
1$#
Red (fixed)
&1-
Green (fixed)
1 &
Measured value dis-
played in red when both
(See
control outputs 1 and 2
note 1.)
are OFF.
& 1
Measured value dis-
played in green when
(See
both control outputs 1
note 2.)
and 2 are OFF.
Note: 1. If the tachometer output mode is set to AREA, howev-
er, the measured value is displayed in red when control
output 1 is OFF and in green when control output 1 is
ON.
2. If the tachometer output mode is set to AREA, howev-
er, the measured value is displayed in green when con-
trol output 1 is OFF and in red when control output 1 is
ON.
Time
Control output ON
Measured value dis-
played in green when ei-
ther control output 1 or
control output 2 is ON.
Measured value dis-
played in red when either
control output 1 or control
output 2 is ON.
27