Controlling MM420 Via Profibus

Dhiyia

Hi Experts
I'm using Drive ES function blocks in order to data exchange between the MM420 & S7 via Profibus,

The MM420 is showing the following act. Frequency values at certain set point:

4000 Hexa = 50 Hz

3000 Hexa = 37.5 Hz

2000 Hexa = 25 Hz

1500 Hexa = 16.4 Hz

1000 Hexa = 12.5 Hz

500 Hexa = 3.91 Hz

My question is:

According to the above values, the MM420 is notrunning in linear curve or linear scale

In fact it is already run in linear scale.

linearity should is not between actual speed and set point in hexa. but it should happen between actual speed and set point in dec.

To sent a set point between 0 - 100% of full scale ( NB. 100% here is equal to P2000 of MM4 parameters if and only if it is less than or equal to maximum frequency).

for example.

if max. frequency is 50Hz.

P2000 = 50

0 - 100% = 0 - 50Hz can be achieved by sending setpoint values between 0 - 4000Hex.

From above table, if you draw a curve between value in DEC & Hz, it will be a linear curve.

Dhiyia

(at 1500h & 500h), because the drive MM420 speed is get reference from analogue signal input (4 – 20 mA)to CPU314C-2DP

I think it suppose at:1500 h = 18.75 Hz instead of 16.4 Hz

and also at500 h = 6.25 Hz instead of 3.91 Hz

Please advise how to solve that problem …

Thank u for your valuable reply….

For scaling between / 0.0 – 100.0 % (Real) & 0 - 16384 (DEC) /

Is there any converting function/instruction in order to convert from DEC format to Hexa format

Thank u for your time…