Overtrace is a browser-based industrial telemetry overlay tool. You load datalogs from multiple modules — compressors, gen skids, engine ECMs — and overlay every channel on one shared time axis so you can see what happened, and when, across the whole system at once.

Which datalog formats does Overtrace support?

Overtrace auto-detects Emit (Dynamic Controls), Caterpillar, Waukesha and Excel datalogs, with more formats coming. Just drop the files in and the channels are parsed and plotted automatically.

Is my telemetry data uploaded to a server?

No. All parsing happens entirely in your browser using local JavaScript in a Web worker. There is literally no upload endpoint — your datalogs never leave your machine. That privacy-by-architecture is a core part of the design.

Do I need to install anything?

No install required. Overtrace runs in any modern browser on desktop, laptop or field tablet, and works even on a spotty plant network because everything is client-side.

Can I try Overtrace before buying?

Yes. The full-featured demo runs on built-in sample telemetry, so you can try measuring, overlays and alignment for free. A license unlocks uploading your own logs, and it is tied to your account rather than a single device.

Faults & codes — every diagnostic in the log

A datalog usually knows why the unit tripped — the information is sitting in a diagnostic message or a boolean channel, several hundred rows down. The Faults & codes view collects all of it in one list and gives every entry a way back to the moment it happened.

Open it from the View menu in the top bar. It is available on every plan, including the demo.

Where the entries come from

Active · DM1 — diagnostics the ECM was broadcasting as currently active while the log was being recorded, decoded from J1939 DM1 messages in a Caterpillar CAN capture.
Logged · DM2 — previously-active diagnostics the ECM had stored, decoded from DM2 messages.
Event flags — named alarm, shutdown, trip, lockout and failure channels from Emit, Caterpillar and COMTRADE logs. These carry no SPN-FMI code, so they are listed by name.

A boolean channel that never asserted anywhere in the log is not listed — a fault that did not happen is not a fault. Ordinary status bits such as “Compressor Running” are not diagnostics and are left in the sidebar where they belong.

Reading a row

Code — the SPN and FMI, for example 110-16. A small “?” means the pair had no exact entry in the code table, so the description is the SPN's name plus the standard FMI text rather than a Caterpillar-specific one.
Description — the decoded fault and its condition, including the cylinder number when the SPN identifies one.
Module · ECM — which loaded log it came from, and which node on the bus reported it.
Occ — the occurrence count the ECM reports it has counted over the unit's life. It is usually larger than what this log contains, and that difference is useful: it separates “first time” from “this again”.
Asserts — how many times the fault went from clear to asserted inside this log.
Active — total time asserted within the log. A fault still asserted at the last sample is counted to the end of the log.
First seen / Last seen — timestamps in the same units the chart's time axis is using.

Filter with the segmented control — All, Active · DM1, Logged · DM2, or Event flags — or type into the search box to match a code, a description or an ECM.
Tick “Only in current range” to hide anything outside the window you have zoomed to.
Click the row. That fault's flag goes onto the chart and the row lights up so you can see at a glance what is currently drawn. Click it again to take the flag back off.
Arm as many as you want to compare — clicking a row never moves the time range, so a second and third code do not throw the window you are looking at.
Use the row's “Jump” button when you do want the chart moved to the moment the fault was recorded. “Clear” in the header takes every flag off at once.
Plot the channels you want beside it — the flag marker stays on the chart with the fault's name on hover.

“Copy list” puts the whole table on the clipboard as plain text, including the recommended procedure for codes that carry one — useful for pasting into a service report.

Privacy

Decoding happens in your browser like every other parse Overtrace does. No log, no fault code and no unit identifier is uploaded to a server.

FAQ

How do I decode SPN and FMI codes from a Caterpillar log?

Load the CAN capture into Overtrace and open View → Faults & codes. DM1 and DM2 diagnostic messages are decoded in your browser into readable descriptions, split into active and logged, with occurrence counts and timestamps.

What is the difference between DM1 and DM2?

DM1 is what the ECM was broadcasting as currently active while the log was recorded. DM2 is the previously-active diagnostics it had stored. Overtrace lists them separately because they answer different questions.

Why is the occurrence count higher than the number of asserts?

Occurrences are what the ECM reports it has counted over the unit's life; asserts are what this particular log contains. Comparing the two tells you whether the fault is new or long-running.

How do I show more than one fault code on the chart?

Click each row in View → Faults & codes. Every row you click adds that fault's flag to the chart and stays highlighted; clicking a highlighted row removes it again. Clicking a row does not move the time range, so several codes can be armed without losing the window you are looking at — use the row's Jump button when you do want the chart moved.

Does the Faults & codes view work on Starter?

Yes. It is available on every plan, including the demo, on any loaded log that carries fault codes or named alarm flags.

Why does a fault show a '?' beside its code?

The SPN-FMI pair had no exact entry in the code table, so Overtrace shows the SPN's name with the standard J1939 FMI text instead of a manufacturer-specific description. The code, counts and timestamps are still exact.