The short answer
- Choose ModLens if you often work without a reliable register map, need to find which register, data type, byte order and scale match the value on a display, or want a tool that logs and serves a dashboard from a laptop or a Raspberry Pi left on site.
- Choose Modbus Poll if you need Modbus ASCII, UDP or secure Modbus (TLS), direct Excel logging or OLE automation from VBA/Python. It's mature and widely used.
- Choose a free tool (OpenModScan, Chipkin Modbus Explorer, QModMaster) for basic polling and device discovery at no cost.
Feature comparison
| Feature | ModLens | Modbus Poll | ModScan64 | OpenModScan | Chipkin Modbus Explorer | QModMaster |
|---|---|---|---|---|---|---|
| Find a known value (search registers, formats, byte orders and scales for the number on a display) | ✓ with re-check | not stated | not stated | not stated | — (scan the list by eye) | not stated |
| All formats side by side | ✓ | — (per cell) | not stated | — (per window) | ✓ (4 orders) | — (per table) |
| 32/64-bit integers and floats, 4 byte orders | ✓ | ✓ | float, other types not stated | ✓ | ✓ | float, global order |
| Unit ID and register scans | ✓ | ✓ | not stated | ✓ | ✓ | not stated |
| IP subnet scan | ✓ | not stated | not stated | not stated | ✓ | not stated |
| Named tags with units, scaling, alarms | ✓ | names; colour rules | not stated | not stated | scaling manual | not stated |
| Live trend chart | ✓ | ✓ (12 series) | not stated | not stated | not stated | not stated |
| Value logging to file | CSV, resumes after reboot | CSV / direct to Excel | disk file (scripts) | traffic log | message log | traffic log |
| Headless 24/7 on Raspberry Pi + web dashboard | ✓ | — | — | — | not stated | — |
| Plain-language errors with "what to try" | ✓ | not stated | not stated | not stated | troubleshooting guide | not stated |
| Modbus TCP / RTU | ✓ / ✓ | ✓ / ✓ | ✓ / ✓ | ✓ / ✓ | ✓ / ✓ | ✓ / ✓ |
| RTU over TCP | ✓ | ✓ | "tcp tunneling" | ✓ (scanner) | not stated | not stated |
| Modbus ASCII / UDP / TLS | — / — / — | ✓ / ✓ / ✓ | ✓ / not stated / ✓ | not stated | not stated | not stated |
| Raw traffic monitor | — | not checked | ✓ | ✓ | ✓ | ✓ |
| Excel / OLE automation | — | ✓ (VBA, Python) | ✓ | not stated | not stated | not stated |
| Platforms | Windows, Linux, Raspberry Pi | Windows | Windows (+ iPhone app) | Windows, Linux | Windows, Linux | Windows (Linux: compile) |
| Price | $89 one-time (launch), 14-day trial, free Lite | $129 one-time, 30-day trial with 10-minute sessions | $99.95 one-time | Free | Free | Free |
What's genuinely different about ModLens
1. Find the register behind the number on the screen
Type the value the device shows, for example 21.2 °C. ModLens reads the registers of the unit IDs you choose and decodes each one as int16, int32, float32, 64-bit values and more, in all four byte orders and with common scale factors. The closest matches come first. Change the value on the device and click Re-check, and only the real register stays. We haven't found this documented in any of the tools above.
2. A logger you can leave on site
ModLens runs headless on a Raspberry Pi as a service. It logs tags to daily CSV files, resumes after a power cut and serves a password-protected dashboard to any phone or PC on the network. The other tools are desktop applications.
3. Explanations, not just error codes
Every Modbus exception and connection problem comes with a "what to try" checklist (unit ID, serial settings, A/B wiring, address offset, table, block size). Every term has a (?) explanation.
Where the others are stronger
- Protocols: Modbus Poll supports Modbus ASCII, UDP and secure Modbus (TLS); ModScan supports ASCII and secure Modbus. ModLens doesn't.
- Excel and scripting: Modbus Poll logs straight into Excel and can be automated from VBA or Python.
- Traffic analysis: most of these tools show the raw frames on the wire; ModLens focuses on decoded values.
- Track record: ModScan dates back to 1990 and Modbus Poll is at version 13. ModLens is new.
- Price: OpenModScan, Chipkin Modbus Explorer and QModMaster are free and good for basic work.
Try it on your own equipment
The best comparison is your own devices. Every ModLens download includes a 14-day Pro trial with no card and no account, and it can run next to the tool you use today.