No setting keeps the on-screen trend across a project download; the trace belongs to the running project and clears with it. Save a picture of the pages, enable data logging to USB or SD storage on the trend object, retrieve the text file by FTP, web page or scheduled e-mail, and download changes only after the log is writing.
No. On this class of 12-inch panel, no option keeps the current trend's history across a project download. The trace on the page belongs to the running project, and a download replaces the project. Two things follow. For the history on the screen right now, capture a picture of it, because the samples cannot be pulled back off the page. For every download after this one, record the samples to a text file on removable storage while the trend runs, and retrieve that file before you touch the project again. This page walks through that setup and the arithmetic for sizing the log.
Why the download takes the history with it
The trend page draws its trace from samples the panel holds with the running project. A project download replaces that project on the panel, and the working trace clears with it. On this panel family there is no option that carries the trace across the replacement. The page also shows only the most recent block of samples, sized by the trend object's Total Stored Samples setting, so the visible history was never an archive: it is a rolling window, and how many samples the page can hold is a fixed number you set, not a growing record.
What you can still save today
Before you change anything, open every trend page and screenshot or photograph it with the pen legend, the Y-axis scales and the time span visible, and write down which PLC tag feeds each pen. That picture is a visual record. It is not a data backup: it carries no per-sample timestamps and no values behind the pixels, so it supports a report or an eyeball comparison and nothing more. If engineering needs the numbers, raise it now. Those samples are gone the moment the project downloads, and storage added afterwards recovers nothing.
What you need
- USB or SD removable storage the panel reads, with free space for the log (the example below sizes it).
- A backup of the project as it runs now, taken before you edit anything.
- The tag list for each trend pen, from the notes you just made.
- A retrieval path: an FTP client or a web browser on your PC, or an e-mail account the panel can send to.
- Spreadsheet software to open the text file.
Turn on file logging before the next download
On these panels the logging setup lives on the trend graph object itself: the object that displays the data is also the one that records it, and trend data logging writes tag values to a file on USB or SD storage. Work in this order.
- Back up the running project, then open it in the programming software.
- Select the trend object on the first page and enable its data logging. Set the destination to the removable storage; the panel writes a text file of tag values there.
- Set the sample interval, and choose the span and the interval together: the same rate decides how far back the page can display and how fast the file grows.
- Repeat for each trend object that needs a record.
- Set the retrieval path (next section) while the project is still open.
- Download the revised project. The old trace clears; you accepted that loss when you took the pictures.
- Let the log run through one shift, then retrieve the file and copy it off the storage.
Pick a retrieval path
| Path | What you set up | Pick it when |
|---|---|---|
| FTP | FTP access to the panel, an FTP client on your PC | You collect files on demand from the engineering network. |
| Panel web page | The panel's web pages enabled | You want to grab the file from any PC with a browser. |
| Scheduled e-mail | The panel's mail settings and a schedule, such as once per shift | Nobody should have to remember to collect anything. |
The file is the same text file in every case; the path only moves it to your PC.
Example: sizing the log for a 12-inch panel at a 10-second interval
Inputs: one 12-inch panel with trend pages and no removable storage configured yet, which is the case at hand. One trend sampled every 10 seconds, taken as an illustrative interval; read your own rate off the trend object before you size anything. A shift of 8 hours. About 30 characters per line, which is what a timestamp, a comma and a value take in text.
Rule in words: lines equal the window divided by the interval, and the file size equals the lines times the characters per line.
Arithmetic: 8 h × 3600 s/h = 28,800 s. 28,800 s ÷ 10 s = 2,880 lines per shift. 2,880 lines × 30 bytes = 86,400 bytes, about 86 KB. Three shifts a day give 8,640 lines, about 260 KB, and a 30-day month of three-shift days gives about 7.8 MB.
Decision: at these sizes, capacity is never the constraint; retrieval discipline is. Log one file per shift, copy it off on that schedule, and a project download then costs you only the samples taken since the last copy. That is the threshold to hold yourself to: above one shift of unsampled data at risk, retrieve the file.
How to check it worked
- Retrieve the file the way you configured it and open it in a spreadsheet as comma-separated text: one timestamp column and one column per pen.
- Count the rows against the arithmetic. One 8-hour shift at a 10-second interval should show about 2,880 rows; wait 5 more minutes and about 30 new rows should appear.
- Prove the property this setup exists for: make a trivial project edit, download, then retrieve the file again. The rows written before the download must still be in the file.
- If the file does not appear, check the destination setting on the trend object and the storage connection. If FTP or the web page misbehaves while the other answers, the split between a dead web server and working FTP is its own problem to work.
- Do not clear storage in the panel until the copies are off it and open; archive USB log storage before clearing it.
When the samples belong in the PLC
If the requirement is that the panel itself shows last week's history after any download, the panel's own file log serves the report, not the page. Hold the samples in PLC memory and point the trend at the controller's retained values: a project download to the panel leaves what the controller holds alone. That path costs PLC program work and caps the history at what the controller can retain, so it earns its keep where the trend is a production record, not an engineering convenience.
The decision
Recommendation: For the case at hand, take the pictures and pen notes, enable data logging on each trend object with USB or SD storage as the destination, and download that change as its own project version. Retrieve the text file on a fixed schedule, once per 8-hour shift at a 10-second interval, and keep the copies off the panel. Move the samples into PLC memory only when the trend must reappear on the panel's own pages after every download.
Questions
Is there a setting that keeps the live trend across a project download?
No. On this panel family the working trace is tied to the running project and clears when the replacement downloads. The supported path is file logging to removable storage, configured on the trend object before the download that matters. Enable it, confirm the file is filling, and the download costs you only the minutes since the last retrieval.
Does inserting a USB stick start trend logging?
No. The storage only receives samples once data logging is enabled on the trend object and that project has been downloaded to the panel. Until then the stick sits idle, and the first download you make to enable logging still clears the current trace, so take your pictures and notes first.
How do I open the trend file in a spreadsheet?
Import it as comma-separated text. You get a timestamp column and one column per pen; set the delimiter to the comma, check the timestamp format the panel writes, then chart the pen columns against time. Keep the raw file unchanged and work on a copy, so the original stays a record.
How often should the panel e-mail the log file?
Match the schedule to the interval. At a 10-second interval, one 8-hour shift is about 2,880 lines or 86 KB, and a three-shift day is about 260 KB, small enough for mail. Once per shift keeps each file readable and limits what one missed retrieval loses.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.