Dear reader,

I would like to "widen" my analog output signal in order to make more precise adjustments.

Please let me explain;

My v20 drive runs in a machine with maximum speed at 15 meter/ min. The V20 is putting out  a 0-20mA  signal referring to actual freq. P0771 = 21

While the machine is running at it's maximum speed 15 meter/min. the analog output is only reading 8,8 mA because the V20 is not running at full speed,so  it's behaving normal, no problem so far.

Since i would like to have a adjustable setpoint from where a burner will be switched on / off i installed a "treshold relay". The analog output from the V20 is triggering the treshold relay.

the treshold relay has an input 0-10V so i put a 500ohm resistor parallel to the analog wires to become a 0-10V signal. Also no problem till here.

The treshold relay holds an tiny potentiometer to set the treshold and it's way too sensitive to any adjustment because i only have 44% of the full scale (0-8.8 mA in stead of 0-20mA).

Now my question is; can i configure a scaling of AO by P0777 to P0780 in the way the V20 gives out 20mA at AO where it gives out 8.8 right now? (while putting out 0 mA where it's 0mA right now so "widening"the  signal) And most important; i don't want to effect the behaviour of the complete machine or the ratio to the other 4 V20's. I only wish to make changes to the analog output.

sorry for explaining my problem in broken english, i'm a mechanical mechanic trying to solve an electric challange.

thank you for reading, best regards Jan

Hello,

I think you are right use from P0777 to P0780

If your P0771= 21 (default 50Hz)

So you need enter:

P0777=0 Hz

P0778=0mA or 4mA

P0779=15 Hz

P0778=20mA

and then i think scaled will be to 0-15Hz 0/4mA-20mA

Thank you very much mr. V !

Following this manual; v20_operating_instructions_complete_en-US_en-US.pdf

i see the the following;

P0777 x1  -9999 <> 9999 % output scaling  (but think 0%  is same as 0HZ)

P0778 y1  analog output scaling  0-20  (so 0 or 4(mA)  will do the job)

P0779 x2 of analog output scaling -9999<>9999% (default 100% so i need to calculate *)

P0780 y2 of analog output scaling 0-20  (keep it on default 20mA)

The calculation i assume to be made; 20mA / 8.8mA = 2.27 so the percentage of increasing the output value will be 227% ?

Thanks again

 Hi AutoGen_4977088,

44% of the full scale as mentioned below, how much % you required for output for your application?

AutoGen_4977088

Dear reader,

I would like to "widen" my analog output signal in order to make more precise adjustments.

Please let me explain;

My v20 drive runs in a machine with maximum speed at 15 meter/ min. The V20 is putting out  a 0-20mA  signal referring to actual freq. P0771 = 21

While the machine is running at it's maximum speed 15 meter/min. the analog output is only reading 8,8 mA because the V20 is not running at full speed,so  it's behaving normal, no problem so far.

Since i would like to have a adjustable setpoint from where a burner will be switched on / off i installed a "treshold relay". The analog output from the V20 is triggering the treshold relay.

the treshold relay has an input 0-10V so i put a 500ohm resistor parallel to the analog wires to become a 0-10V signal. Also no problem till here.

The treshold relay holds an tiny potentiometer to set the treshold and it's way too sensitive to any adjustment because i only have 44% of the full scale (0-8.8 mA in stead of 0-20mA).

Now my question is; can i configure a scaling of AO by P0777 to P0780 in the way the V20 gives out 20mA at AO where it gives out 8.8 right now? (while putting out 0 mA where it's 0mA right now so "widening"the  signal) And most important; i don't want to effect the behaviour of the complete machine or the ratio to the other 4 V20's. I only wish to make changes to the analog output.

sorry for explaining my problem in broken english, i'm a mechanical mechanic trying to solve an electric challange.

thank you for reading, best regards Jan

Hi jack,

Thank you for asking, i would like to have 20mA (10V) while the machine is running at it's maximum speed.

The V20 is not at it's maximum at that point.

At maximum MACHINE speed the V20 is putting out 8.8mA which i convert to 0-10V by using a resistor 500 Ohm.

So the machine-speed range is only represented by a range of 0-4.4V while the treshold-relay input is ranging from 0-10V, adjusable with a potentiometer.

Setting the potentiometer is not accurate eneough due to the restricted working range.

To become full range at potentiometer i would like to increase the analog output of the V20 with 227%.

kind regards Jan

Hello,

Please check p2000 value, it is reference value i.e. 100% .e.g. if motor max rpm = 1500 rpm & max frequency is 50 Hz, then p2000 = 50. r0021 output value is scaled to reference of p2000 i.e. p2000 = 100% = 4000 Hex =  1500 rpm. 

So please check value set in p2000 in your case & correct it so that output value will be correct.

Hope this helps.

Hi Piscean,

Thank you for answering, sorry for late reply, i was out off workshop yesterday.

It's a good point to check P2000, P2000 is set at 100 so 50 would double the value at analog out!

I was almost changing that parameter (with help off the mobile phone using wifi) when the Siemens software warned P2000 also effects other behaviour.

Since the (locked) PLC code on  the machine is managing the machine speed (off totally 5 V20's ) i can't change P2000 cause that V20 will become out of synchronisation.

So i dicided to order a open source mini PLC to get ultimate freedom in handling analog out. our machine is running all week long so i can't take it for some experiments.

I would like to thank all people here for their helpfull suggestions, much appriciated!

kind regards Jan