Monarch Instrument ACT-3 - Manual (Page 7)

2
user. A moment later it measures the input frequency again. The difference of these two,
scaled frequencies is divided by the time interval between the two measurements. Several
measurements are averaged then displayed.
The scale factor allows the user to scale the input to obtain a read out in any units required:
RPM per Minute (RPMPM), inches per second per second, meters per hour per minute,
yards per fortnight per second, and so on. The scale factor may be set anywhere from
0.0001 to 9999.9.
The SCALE menu selection is used to set the scale factor. Without any scaling (Scale = 1),
the tachometer measures in pulses per second per second. This is the rate of change of the
number of pulses per second over a second. To get a readout in RPMPM in a system with
P pulses per revolution set the scale factor to 3600/P.
Pulses Revolution 60 second 60 second 3600 Revolutions
———— * ————— * ————— * ————— = ———— * ——————
Second 2 P Pulses Minute Minute P Minute 2
Which is Revolutions per minute per minute.
For example, the scale factor to display in RPMPM for a 68 tooth gear would be 3600/ 68
= 52.941.
In this mode:
The display is updated up to once every two seconds with the average Rate of Change.
The throughput of the max/min, analog outputs, and relays is up to about 2 times a
second.
Press the SET and RESET buttons together to temporarily show the last RPM (Input
frequency * 60) measured.
The display will show a positive number when the frequency is increasing and a
negative number when the frequency is decreasing.
Otherwise this mode behaves like the SCALE mode.
In order to support negative numbers when editing set points, zero scale and full-scale
values, press the SET and
∨∨∨∨∨ buttons together to toggle a minus sign in the left most position
on the display.
Remember that even a small change in RPM over a short time will cause a large Rate of
Change (average acceleration) to be displayed. The gate time for each measurement is about
1/3 of a second. For instance, if you use a digital function generator to change from 3000
RPM to 3001 RPM, the change will happen all at once. You will see that it happens within
1/3 of a second. So 1 RPM change in 1/3 of a second is 180 RPM over one minute or 180
PRMPM acceleration.
1.1.6 Totalizing Mode
In the Totalizing Mode, each input pulse causes the display to be incremented by a
constant value that is set by the user. This enables the user to scale the input to obtain a read
out in any measure required: number of inches, number of bottles, number of revolutions,
and so on. The scale factor may be set anywhere from 0.0001 to 9999.9.
1.2 Decimal Point
The decimal point on the display may be fixed (set) in position or floating (auto-ranging).
21
Once you have the correct scale factor entered, press and hold the SET button and press the RESET
button once. The display will show donE and the SCALE. Release the buttons and then press the
RESET button once to return the unit to normal operations.
Note that all limits and outputs work in the absolute displayed value. Thus, if you have entered a scale
factor to display in yards per minute, then the limit display and setting will be directly in yards per
minute.