Universal Front End for Industrial Controls, Anyone?

A DVM?

Why not have an auto-ranging voltage divider with AC and DC mode just like a DVM has? Then the output is further scaled down to match the current draw of LED, by use of a resistor network.

auto-ranging voltage divider Yes! Those are the magic search words.

So did you actually find something related to that term?

Something like this?

https://www.amazon.com/12-250V-Digital-Detector-Light-Electric/dp/B01M5LDA06

Isn't that actually called a widget?

No it's called a KAGU....

Looks like Dr. Who's sonic screwdriver to me.

Fake!

I forgot about those devices. They are really cool but not what I was looking for.

I bet you could get $10^⁶ for a functioning unit of Dr. Who's screwdriver.

I understood that you wanted a light for a standard voltage level, in which case you have the so called pilot lights.

Unuversal line voltage (about 85 to 265V single phase) is for what Power Factor Correction rectifiers are built, since they are required for Electeomagnetic Compatibility in high power devices.

Even phone chargers have them inside (you can check yours) so you probably could use it for monitoring. It will not give you the dynamics of a voltage divider but I do not think 1ms time response is reasonable anyway.

Rockwell and Schneider make sensors suitable for use ac or dc 24V up to 260V, same sensor, just like you can plug your laptop power supply from 100 to 240Vac.

Do a search on this item 871TM-B10N30-A2, 2 wire prox switch ac/dc, 20 to 250V ac or dc

magnetic proximity switch

Is this what you were referring to? I did search based on your character string, and it was a motley assortment of web pages.

Here is a link to Rockwell, as an example of a universal sensor that can be applied to any particular digital plc input, for instance. Not exactly sure what OP's original point was, thinking this might be it...

http://ab.rockwellautomation.com/Sensors-Switches/Inductive-Proximity-Sensors/871TM-Stainless-Steel-Proximity-Sensors

From the AB website - "10...30V DC or 40...250V AC/DC units available" (my emphasis).

It is the same piece of equipment, often used in industrial applications so you don't need to stock different sensors. Prox is only one example of this digital io circuit.

I think the or is redundant, or for covering rare cases where someone might want to use this on a circuit with both ac and dc (such as superimposed sine wave on a dc offset), this is a single unit two wire sensor ac/dc, listed on the further selection details

You have not given what you regard as "consuming much power", which makes it difficult to answer. Nor have you given limits for "loss of signal" - do you expect it to recognise 3V3 logic & PLC High & Low limits?

Too sensitive can be a bane - I had PLC AC outputs with small capacitors built-in - enough leakage for 110VAC "motor" driven panel hours counters to creep round when they were supposed to be off - I have read of AC relays latching-on because cable capacitance resonated with the coil inductance. DC PLC outputs can have a minimum load too.

I made a box of 6 of these up a long time ago along with the sockets, plugs & wires for hooking-up to plant. It works on DC of a few volts too. I was faced with supplies at different voltages, some earthed, some floating & need to interface to a counter - timer (earthed) which had a DC 5V supply output. Obviously, a battery/DC supply is needed for the indicator side.

The DCS world is trying to grapple with universal I/O, however high level 115Vac discretes have not yet made it into such a design.

The White paper at this URL

https://www.emerson.com/documents/automation/56728.pdf

describes the rationale for Universal modules in the DCS world, and provides examples of configuration, where the specific type of analog input is configured. I note that there is a section on Relay outputs, but I did not read it closely enough to see whether relay outputs are a different module that plugs into the base.

Honeywell has a universal 16 channel I/O module for its ControlEdge process PLC with a choice of any of the following for each of the 16 channels:
- 4-20mA AI, (no thermocouple or RTD)
- 4-20mA AO
- 24Vdc DI
- 24Vdc DO

http://www.lesman.com/unleashd/catalog/control/Honeywell-ControlEdge-PLC/Honeywell-ControlEdge-PLC-ds-CE03-100-130v1-2016-09.pdf

115 VAC is used at the output end of many relays connected to PLC/HMI systems.

It is the prime move for valve switching by either electrical or pneumatic switching of the valves. It is either on or off, and is digital in that sense, and is connected to a control system.

Analog (typically 4-20 mA) is used for valve positioning, where in olden days there used to be pneumatic valve positioners based on a complicated scheme of controller air regulators. Then cam I-P converters, then they did away with air control on many valves.