Industrial Replacement for Digital Dial Gauges (0–25 mm) with RS-485 / PLC Interface

I’ve used CCD laser displacement gauges to measure small variations in distance on industrial machinery. However, getting 0.01 mm resolution on a 25mm span could be a problem. You could be looking at a 0-16384 A/D or more. I have used Banner Engineering and Keyence displacement lasers for machinery, where the measurement path is relatively clean and uniform. High humidity shifts and dust & dirt could create a problem.

Other solutions include LVDT sensors, but I have no practical experience with design and application of these type sensors.

You present a lot of details here, but you still leave out some critical information.

What signal interface comes out of the digital gauges? A suitable off-the-shelf signal conditioner with an RS-485 output for each gauge would probably be better. The multi-drop feature of RS-485 connects all six gauges to one input port of the PLC. Debugging a custom Arduino interface, even if you have the source code, can become a difficult project itself.

"Displacement" implies motion is being measured. The settling time of the mechanics is probably the biggest concern, but the electronics also have a settling time.

Dear Sir,

I’m sorry, but there is no information mentioned in the gauge specification sheet regarding the communication details. At the moment, it appears to be a kind of black box. I would like to replace these gauges with a proper industrial-grade solution.

Don't be so lazy. If you cannot locate documentation for these gauges, then do the reverse engineering. Like it or not, the mechanical accuracy relies on using those gauges. The measurements from the gauges are somehow entered into the Arduino. Investigate how they get there. Most likely, the gauge reading to the Arduino is an analog voltage level. Analog voltage to RS-485 Modbus Input modules are readily available. Another possibility is getting just a suitable analog input module for the unspecified PLC. Thus, the analog levels will be directly available to the PLC processor with the least amount of latency.

If you are looking for a solution that is ‘Remove and discard existing, replace with new set of integrated gear’, these guys can fix you up:

https://www.globalgilson.com/consolidation-data-acquisition-software

Remarkable find, has the displacement and accuracy, LVDT design is robust.

However, the data acquisition system is canned, and could be a ModBus application, which is difficult and not necessary easy to develop on an industry standard PLC, voice of several years of experience over a few decades.

However, those LVDTs are likely available in a 4-20mA output, and use of a 32 bit high resolution analog input such as available from Rockwell 1794 I/O would give you the resolution you are looking for and the industry standard solution that thousands of techs in the US know inside and out.

Hi,

I have selected a Chinese MIRAN brand LVDT, model MIRAN LVDT20-R-30mm-DL-A-2/Y, which has RS485 communication and 16-bit resolution. I plan to connect it directly to a Weintek HMI for data logging.

Thank you all for your valuable time and helpful suggestions.