Справочник Пользователя для Mitsubishi Electronics FX

FX Series Programmable Controlers

5-60

The number of pulses received at S

1 

are counted

and stored in D

+1

; this is the current count value.

The counting takes place over a set time frame
specified by S

2 

in msec. The time remaining on the

current ‘timed count’, is displayed in device D

+2

.

The number of counted pulses (of S

1

) from the last

timed count are stored in D. The timing chart
opposite shows the SPD operation in a graphical
sense. Note:

¿

: Current count value, device D

+1

¡

: Accumulated/ last count value, device D

¬

: Current time remaining in msec, device D+2

a) When the timed count frame is completed the data stored in D

+1 

is immediately written to D.

D

+1 

is then reset and a new time frame is started.

b) Because this is both a high speed and an interrupt process only inputs X0 to X5 may be

used as the source device S

1

. However, the specified device for S

1 

must NOT coincide with

any other high speed function which is operating, i.e. a high speed counter using the same
input. The SPD instruction is considered to act as a single phase counter.

c) Multiple SPD instructions may be used, but the identified source devices S

1 

restrict this to a

maximum of 6 times.

d) Once values for timed counts have been collected, appropriate speeds can be calculated

using simple mathematics. These speeds could be radial speeds in rpm, linear speeds in M/
min it is entirely down to the mathematical manipulation placed on the SPD results. The
following interpretations could be used;

SPD
FNC 56
(Speed
detection)

Detects the
number of
‘encoder’ pulses
in a given time
frame. Results
can be used to
calculate speed

X0 to X5 

K, H,
KnX, KnY,
KnM, KnS,
T, C, D, V, 
Z

T, C, D, Z (V)
Note:
3 consecutive devices 
are used. In the case 
of
D= Z monitor D8028,
D8029 and D8030

SPD:
7 steps

FX

0(S)

FX

0N

FX FX

(2C)

FX

2N(C)

FX

(2C)

FX

FX

2N(C)

FX

0N

FX

0(s)

PULSE-P

FX

(2C)

FX

FX

2N(C)

FX

0N

FX

0(s)

16 BIT OPERATION

FX

FX

0N

FX

0(s)

FX

(2C)

FX

2N(C)

32 BIT OPERATION

X10

K100

X 0

D 0

SPD

[ S1 ] [ S2 ] [ D ]

2

1

3

X10

S1

S2

S2

Linear speed N (km/h) =

3600 

× 

(D)

n 

× 

S

2

× 

10

3

Radial speed N (rpm) =

 60 

×

 (D)

n 

× 

S

2

× 

10

3

where n = the number of encoder pulses per revolution of the encoder disk.

where n = the number of linear encoder divisions per kilometer.