R.,

Yes – VT_R4 has precision slightly above 6 significant digits. It explains the situation fully. The solution would be to use VT_R8 (or other suitable type) if the server supports it.

Best regards,
<span style="font-family: "Arial","sans-serif"; color: #1f497d; font-size: 10pt">Zbynek Zahradnik

<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'">From:<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'"> R.
Sent: Tuesday, June 07, 2011 9:38 PM
To: Zbynek Zahradnik
Subject: RE: Data.NET Value Precision

Zbynek,

I just wanted to follow up on this and let you know that I think it has to do with what the OPC server is sending us- it’s sending a value in an exponential format (VT_R4 2.054319E+09) so it makes sense that the value is only being displayed as 2054319000. I tested with TOP Server and it retuned the full correct value.

R.

<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'">From:<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'"> R,
Sent: Tuesday, June 07, 2011 2:37 PM
To: Zbynek Zahradnik
Subject: RE: Data.NET Value Precision

Thanks. I will do some testing and try to capture diagnostics.

R.

R.,

The component is not supposed to do rounding. And I do not think it does it, but obviously I cannot rule out a bug, though it would be somewhat weird one.

<span style="font-family: "Arial","sans-serif"; color: #1f497d; font-size: 10pt">Zbynek Zahradnik

<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'">From:<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'"> R.
Sent: Tuesday, June 07, 2011 2:04 PM
To: Zbynek Zahradnik
Subject: Data.NET Value Precision

Zbynek,

I have a customer who has told me the following. They have “an item with a value of 2050505728 in the server is reported in ItemChanged event as 2050506000. The value is rounded.” Is there a way to adjust the precision of the value?

I have not had an opportunity to test this myself to see if I see the same behavior. I can also capture diagnostics, if necessary to see exactly what is being passed to Data.NET, but I thought I would check with you to see if there was a quick property setting to solve this. I wasn’t able to find one that looked like it might work.

Thanks in advance,
R.