Numeric Text Field - Float vs Double Issue

Ignition
1

Overview:

  • I have an Ignition project (Vision) with a single connection to a Modbus TCP compatible device (flow computer).
  • I am using Numeric Text Field to update values in said device. Number Type is configured as "Double".
  • My OPC tag is configured as "Double" precision tag, mapped to the following Modbus register ([testDevice]1.HRD31288.

Problem:

  • Say I want to enter a value of "13.3".
  • If I enter the value of "13.3" in the numeric text box and press enter, the value sent to the device ends up being "13.300000190734863000".
  • If I enter the value of "13.3" in the Visual Property Editor, in the "Value (Double)" field, the value sent to the end device ends up being "13.3" (with a lot of zeroes).

It seems like the Numeric Text Field convers my Double to Single floating point number prior to being sent to the device.

If I change the parameter in the end device instead, it is read correctly into Ignition (i.e. as round "13.3").

Is there something I am missing, or is the numeric entry box always doing a conversion to single precision float?

Value When Entered in Vision Property Editor
Value When Entered in Vision Property Editor1292×608 42 KB

Value When Entered in Text Box
Value When Entered in Text Box1292×608 44.3 KB

Single Floating Point Conversion
Single Floating Point Conversion900×279 26.8 KB

2

This is totally normal and unavoidable with binary numbers in floating point. 3/10 doesn't have an exact binary fraction (least common denominator includes 5). User interfaces typically hide this technicality from operators using some amount of rounding. (At the point of display.)

3

I do understand why some numbers cannot be represented accurately in memory.

However, what I am saying is that when a number is entered via Numeric Text Field, it appears to be converted to 32-bit float, despite the fact that binding, tags and Modbus link are all configured as 64-bit doubles.

Any ideas how to avoid it?

Float vs Double
Float vs Double751×428 18.9 KB

4

Hmmm. Looking closer, I think you are right. The numeric field looks like it is coercing to single precision somewhere. Or perhaps the driver is doing it. Consider testing with my alternate driver.

You should report this as a possible bug. (Open a support ticket.)

5

I will do, I was just hoping that I have made a stupid mistake somewhere, as I tend to blame myself first.