Can you display a negative value on a PanelView550?

[JH14]

Hi, We want to re range a pressure transmitter to read from -250 kPa to +250 kPa. We have no problems with the instrument and SLC but cannot get the display on our PanelView 550 to go to a negative value. Can this be done, if so how?

 

[Gil47]

Yes it can be done + 250, displays as 250 requiring 3 digit spaces , a -250 requires the display to be able to hold 4 digits as negative sign takes up one space.
Thats a possible reason.
Try displaying a number that is -25 for example and see if it displays

What is the PLC brand ?

 

[JH14]

It's a Allen Bradley SLC 5/04. I will try this and see but I have simulated around -50 and it would not display. When have my laptop connected to the SLC I can see the correct value in the scale block no worries. On the PV it displays fine when above zero but once it drops below it reads ***.

 

[Gil47]

Are you trying to display an Integer or a floating point

On the panelview 550 panelbuilder software when you click on the display box what details do you see about the tag thats used

I still feel it should display.

Welcome to the forum

 

[JH14]

Thanks. For the data type I've tried it as a signed and an unsigned integer. Im altering an existing progran and it was found as an unsigned integer. The site is 2 hours away so if there are a few things I could try that would be good. I haven't tried it as a float/real.

 

[Kidblue]

It should work with no problem at all...is the 'MIN' value for the tag you're trying to display set to 0, or do you have a negative minimum value?

Regards,


Rob

 

[JH14]

I have tried both ways, with 0 and -250.

 

[leitmotif]

Hi, We want to re range a pressure transmitter to read from -250 kPa to +250 kPa. We have no problems with the instrument and SLC but cannot get the display on our PanelView 550 to go to a negative value. Can this be done, if so how?

Instead of setting your referance at atmospheric (I assume) ie 14.7 or gage pressure (approx 101 KPa) why not set it at absolute then you do not have to fool around with + /- 250.

I am probaby a bit off on conversions


Dan Bentler

 

[OkiePC]

In the PB32 application, the tag needs to be signed integer (or float). The minimum value will also need to be less than or equal to the lowest value you wish to display. Also, the number of characters in the display field must be enough to hold all the characters plus the decimal point (if any) plus the sign character. So to display -250.0, you need a field length of 6 characters minimum.

Most likely, the field length is too short to hold the minus sign and that is why you saw "***" when you had the signed integer and correct minimum value. For a display only tag, I normally leave the min and max at the default values (-32768 to 32767).

Also verify the scaling. For example, if the raw value at the minimum is -2500 which represents -250kPa, then your scale value would 0.1. In PB32, the scale is mulitplied by the raw value before the number is displayed.

Good Luck!
Paul