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What is the meaning of "prescaler"? It's a multiplier used to multiply the
measured frequency by a programmable value in order to achieve the
desired value on the display.
To allow the scaling capability of the instrument to be as powerful as
possible, this parameter has been divided into two sub parameters:
the mantissa "A" and the exponent "b". The prescaler is stated as
b1
A * 10
.
The calculation capability is from:
-9
9999 * 10
(0.000009999) max. divisor;
-1
1 * 10
(0,1) min. divisor;
9
9999 * 10
(9999000000000) max. multiplier;
0
1 * 10
(1) min. multiplier.
What is the meaning of "pulses per revolution"? It is the number of
pulses that are generated by the input connected sensor for every
complete revolution (360 ) of the wheel or of the drive shaft being
detected.
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For instance, if the wheel has 30 cogs (30 references) that can be
detected by an inductive proximity switch, at the end of its rotation it
generates 30 pulses, so the number that has to be programmed as Pu.1
or Pu.2 parameter is 30. Pay attention: if, instead of a speed or a rate,
you have to measure and display a frequency or a period, Pu.1 and Pu.2
have to be "1" (pulse per revolution).
First example:
if you have to measure a speed of a motor with the following data:
motor speed: 800 RPM;
pulses per revolution : 1;
requested displayed value: 800 RPM;
you have to proceed in the following way:
calculate the maximum frequency that is given by:
"[max. speed (RPM) * pulses per revolution]/60", that takes in our case:
"[800 * 1]/60 = 13.33Hz"
"InP": to select the proper input range that is connected to the
maximum frequency. You have to measure, in our case, 13.33Hz,
therefore the range is "r1" (from 0.001Hz to 500Hz). With the "r1" range
you can easily calculate the minimum speed the instrument can
measure and display: "[min. frequency (Hz) * 60] / pulses per revolution"
that takes in our case "[0.001 * 60]/1=0.06 RPM".
"t.bA": to select the proper time base in order to exploit the maximum
performance of the instrument. If the speed of the motor can be adjusted
from 100 RPM to 800 RPM we can calculate the time period corre-
sponding to the minimum speed that is given by: "60/[min. speed
(RPM)* pulses per revolution]", that takes in our case "60/[100*1]= 0.6
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