Want to show measured value on HMI

Dear All,

I am going to commission some Weighing Scales connected to Measuring/Display Unit BTW-100 (Bikotronic Digital Balance Unit), with S7-315 and Analog Ai8 x 13 BIT (6es7331-1kf02-0ab0)....

BTW - 100: Reads Load Cell and Displays weight in Kgs.......It also gives an Analog Output (which according to Manual) 0-10V= or 2-10V=......................... Imax = 4mA, Rmax= 2.5kohm.......

I am going to use this Analog Output with Ai8 module in S7....

This scale is connected to a SKIP which is dosed with Aggregate (of 3 different sizes) and taken up to Mixer.... Scale is fixed at the bottom and SKIP rests on it...... Dosing gates are just above SKIP and fills the SKIP for required size of Aggregate.....

I measured the Output Analog Voltages as follows :  Pin 1(-), Pin 2(+)

SKIP on the Scale & Empty: Reads (-57 Kgs) and Voltage measured is (-1.3mV)

SKIP on the Scale & FULL :Reads (+2335 Kgs.) and Voltage measured is (+7.87 V)

SKIP on TOP & Scale FREE :Reads (-876 Kgs.) and Voltage measured is (-1.3 mV)

I want to show this measured Value on my HMI....Though Negative Values need not to be shown and may be fixed to 0 Kgs. on HMI i.e All Negative values will be seen as 0 Kgs.....

I am confused to use Measuring Range as +/-10V OR 0....10V

also in FC105 what would be my High and Low Limit ?

Also, what if Negative Voltage gives Error (Under Range/Under Flow) ?

Thanks...

Mr Ansari

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Split from FC105 & FC106 SCALE BLOCKS.

Hello,

I would use the range -10..10 V at the analog module.
Scale the value with FC105.
In my opinion should your min value at the FC105 -57 kg,
the max value should be calculated (20 V/17.87 V * 2335 kg) = 2613.3 kg
20 V = measurement range 

The output value of the FC105 should you connect with the function "LIMIT".
e.g. with this in SCL 

(Value = output of FC105, HMI_Value = value for the HMI)

IF Value <= 0.0 THEN
    HMI_Value := 0.0;
ELSIF Value >= 2335.0 THEN
    HMI_Value := 2335.0;
END_IF;

Hope this helps.

regards
CaOd

Hi CaOd,

Thanks for your response.... Actually value ( -57 Kgs.) is not a fixed value.....Next time the SKIP sits back on Scale, it would read -3 kgs. OR Probably in the morning when you first time switch ON display, it might read +30 kgs.  As this is a big scale, it has errors which shifts 0 point with each cycle or otherwise...

My query is now, May I define Measuring Range in Module as 0....10V and in FC105 ignore any Negative Input and somehow show always ZERO like you shown in LIMIT function....

Also, while in the Morning first cycle, if the display showed for ex. -50 Kgs..then Operator has an option BUTTON there which sets displayed Value to zero......So the scale which was Reading -50, now shows 0 kgs.  and the same MUST REFLECT IN my HMI also..... Now at the same INPUT VOLTAGE, HMI slmust also show 0 Kgs...

Hope you got my point....

Needs your best solution.....

Thanks....

Hi Caod,

Thanks for your response... Actually this value (-57 Kgs.) is not a fixed value for Empty SKIP..... Perhaps, very next cycle it would sit back and display would read -1Kg.. OR Probably next morning with first power ON, display might read +20 Kgs Or -35 Kgs.....

Operator has been provides with a Button ("0"), which changes display to ZERO if previous readings are within permitted range e.g -60/+60....

So the Display at a given Negative Voltage was previously reading say ( -57 Kgs.), NOW for same Input voltage reads ( 0 Kgs.) and now this change must Reflect in my HMI also automatically.....

Hence I was to ask you What if I set Measuring Range 0...10V and Ignore any Negative Input Voltage to FC105 without getting any UNDER RANGE/ UNDER FLOW Error...

Also, I didn't yet check whether OUTPUT ANALOG Voltage should change if Display is manually changed to ZERO.

Hope you understood my query...

Thanks....

Hello Mr Ansari,

if I understand it right then do you want to "calibrate" the display every morning during startup the PLC.

You can use the analog in as 0...10 V and ignore all the alerts.

When you use the 0...10 V then it's not necessary to "calibrate" the input.
Then you don't read no negative values, the minimum value of your IW is 0.

Then can you set at the FC105 the follow:

• LO_LIM = 0.0 (kg)
  
• HI_LIM =  2967.0 (kg) (10 V/7.87 V * 2335 kg)

I hope I understand your problem right.

regards
CaOd