Analog input scaling 0.5v to 4.5v

Hi all,

I'm not new to Logo but a scaling issue has me really stumped! I need to scale a pressure transducer as follows:

Range -1.0 to 9.3Bar

Voltage 0.5v to 4.5v

It doesn't seem to matter what gain or offset I use, I just cannot get it to work correctly. The higher the pressure the great the error! For example at 1 bar it reads spot on but by the time it reaches 5.5bar the Logo is reading 0.5bar adrift. I'm certain its the voltage range of 0.5 to 4.5 that's the issue but I cant rule out my lack of understanding either!!

I have attached the settings I'm using that so far work best.. Any suggestions will be greatly appreciated!!

Thanks, Plazz

 @ixo65:

ixo65

Hello,

maybe you should first give exactly the values of the sensor.
Are the values -1.0 to 9.3 bar the measuring range of the sensor? What does the term 0.5 to 4.5 V refer to? To an output value?

Which signal does the sensor emit? 4-20mA? Or 0-10V?

I can not assign your Information.

 I have seen a Festo sensor that does something like this. It is a 0 - 5V sensor but the top 0.5V and bottom 0.5V is like saturation limits.

The usable linear range is 0.5V for -1.0bar (vacuum) and 4.5V for 9.3bar.

My suggestion is to widen the imaginary engineering scale to handle 0 - 10V and then check for limits.

ixo65

#dP,

then make it.

Thank you for the opportunity.

Hi, sorry I thought I had given the exact values of the sensor but I can see now that it could have been clearer!

The measuring range of the sensor is -1.0 to 9.3bar. It’s a ratiometric sensor and so at -1.0bar the signal voltage is 0.5vdc and at 9.3bar the voltage is 4.5vdc. The supply voltage of the sensor is 8 to 30vdc.

Thanks, Plazz

Plazz

Hi, sorry I thought I had given the exact values of the sensor but I can see now that it could have been clearer!

The measuring range of the sensor is -1.0 to 9.3bar. It’s a ratiometric sensor and so at -1.0bar the signal voltage is 0.5vdc and at 9.3bar the voltage is 4.5vdc. The supply voltage of the sensor is 8 to 30vdc.

Thanks, Plazz

 yes I did understand it correctly.

The example I have posted gives out values from -100 to 930. This needs to be kept in mind. The display of the value is configured to show 2 decimals  -1.00 to 9.30bar.

Hi, Many thanks #dP for your help, are you able to attach your sample program please? either I am missing something or I still cant get it to work satisfactorily!

Regards, Plazz

Brilliant! That works perfectly and rather frustratingly I was already quite close with my own solution! I guess you just can't always see the woods for the trees!! Thank you so much, I can finally switch off and enjoy my Friday evening!!

Kind regards, Plazz