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Second example:
if you have to measure the speed difference between two wheels,
detected by 2 inductive sensors, that have the following data:
Wheel number 1 (connected to the channel "A" of the MDI40):
max rotational speed: 700 RPM;
pulses per revolution: 4.
Wheel number 2 (connected to the channel "B" of the MDI40):
max rotational speed: 600 RPM;
pulses per revolution: 4.
you have to proceed in the following way:
calculate the maximum frequency that is given by:
"[max. speed (RPM) * pulses per revolution]/60", that makes in our
case, for wheel 1: Fa = (700 * 4)/60 = 46.66Hz
for wheel 2: Fb = (600 * 4)/60 = 40.00Hz
•
"InP": to select the proper input range that is connected to the
maximum frequency you have to measure; in our case the value is
between 40Hz and 50Hz, 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 makes in our case "[0.001 * 60]/4=0.015
RPM".
•
"t.bA": to select the proper time base in order to exploit the maximum
performance of the instrument. If the speed of the two wheels can be
adjusted from 100 RPM to 700 RPM (for the first wheel) and from 100
to 600 (for the second one), we can calculate the time period corre-
sponding to the minimum speed that is given by: "60/[min. speed
(RPM)* pulses per revolution]", that makes in our case "60/[100*4]=
sec., therefore the "t.bA" would be "0.6", better if "0.7".
•
"oPr": to perform the measurement of a "speed" you have to choose
the "F1" function
•
"SCA"
•
"Pu.1": the number of "pulses per revolution" is in our case "1",
therefore "Pu.1" becomes 1.
•
"PS.1": the prescaler formed by the two sub-parameters "A1", man-
tissa, and "b1", exponent, has to be set in the following way:
the maximum read-out capacity of the instrument is 9999, that means
the speed can be shown as 800.0 "RPM". We have to measure "800"
but to obtain the maximum speed resolution we have to display 8000
(don't consider the decimal point). The calculation made by the
instrument according to function selection "F1" is the following:
value to be displayed = (Fa * PS.1) / Pu.1 (1)
- "Fa" according to the frequency of 800 RPM is 13.33Hz;
- "Pu.1" is 1;
- "PS.1" can be calculated from the above mentioned formula (1) that
means: (value to be displayed * Pu.1) / Fa, that makes :
(800*1) / 13.33 = 60.01, that means: 60.01 = A1*10
b1
therefore A1=6001 and b1 = -2 (10
b1
→
0.01)
•
"dSY": to show on the display 800.0 we have to move the decimal point
to "111.1";
•
"Lo": see the proper explanation on the next pages;
•
"Hi": see the proper explanation on the next pages;
The PS.2 menu is not available for the functions F1, F6 and F7.
Summary of Contents for MDI 40 TF - CONFIGURATION SOFTWARE
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