Tag history pen problem

Good morning guys,

I’m here again to ask for your help with Ignition.
In my project I’ve created a lot of trend with history pens with no problem, except one of that as you can see in the attachment. The green pen is a flowmeter used to fill a tank of various products. I fill the first, the I reset the count of the flowmeter, I fill with the second product and so on until the settings of the recipe.

As I say, once I reach the recipe value, I close the valve of that product and I reset the flowmeter count, so the value is set to ZERO, as you can see especially is the last load, the historycal value is not recording zero (I assure you that the actual value change to zero, I check more times), but it looks like the trend is making an average and it decrease very slow and I really can’t understand the reason.

Please tell me if you need more data to understand the problem.
Thank you very much guys!

Can you try changing (I think it’s) the deadband style from auto to discrete and test it again

The issue looks to be that no value is being recorded for the zero value until the tag’s automatic Max time between samples forces it to log a value (30 mins). The straight line you see connecting the points is an interpolated line between two points, the first at 6:17:xx and the second at 6:47:xx 30 mins later.
You can try changing the chart’s mode from Fixed to Raw so that the raw data is plotted instead of showing interpolated data with x samples. Also try changing the tag chart pen from analogue to digital so that it shows discrete changes

What are the flowrates/totals values on the graph? The y axis labels are cut off. I’m not entirely sure why it wouldn’t record the 0 when it changes, as it looks like this should be far greater than the deadband.

The values of the flowrate can change from x.xx to xx.xx, in any case it’s a float number with always 2 decimal points. During the day I thought about the tag’s automatic Max time between samples forces (30 min) and so I change the sample mode from On Change to Periodic 1 sec and this problem disappear.
Actually I don’t like how I solve it because I have a lot of time during the day where I save into the database even if is not needed.
I’ve just tried to chage the chart’s mode from Fixed to Raw and even in this case the problem disappear but the trend is not showed nice as is in Fixed mode.

Now I try as you suggest, changing the deadband style from auto to discrete (I back with the sample mode to On Change) and I will see how it will work.

Thanks for the help, I will let you know how this move on.

I check now, changing from Auto to Discrete has resolved the problem, the trend in not so accurate (I think because of the interpolation, but it could be a good compromise. We’ll talk about it, if is ok like this or if is the case to save the tag periodically.
Thanks again for the help!