Wireless sensors into the 4-20 mA input your SCADA already has.

Yes, it can feed the 4-20 mA input you already have

That is the question almost everyone arrives with, so here is the answer before anything else. A Meterra wireless sensor can deliver its reading to your existing 4-20 mA input. Not a replacement input, not a new panel, not a different control system. The one that is already landed on your terminal block and already scaled in your PLC or SCADA.

And the second question, which always follows: no, you do not have to replace anything. Your control logic, your operator screens, your alarms, your historian, and your integrator’s work all stay where they are. We are adding a source of readings, not taking over a control system.

What the bridge actually is

There is no mystery in the hardware, so we will just describe it.

The sensor goes wireless. A Meterra ultrasonic or submerged pressure sensor mounts at the tank, pond, lagoon, or manhole and reports over low-power cellular, Verizon NB-IoT by default, with satellite for sites that have no signal at all. No trench, no conduit, no new wire run to the field.

A small computer sits at your facility. It is a single-board computer, Raspberry Pi class, in an industrial enclosure. It receives the wireless readings.

That computer emulates the signal your system expects. For a legacy input, it drives a 4-20 mA current loop output, scaled to your range. Your PLC or SCADA reads current on a pair of wires, which is exactly what it has always read. It cannot tell, and does not need to know, that the measurement arrived over a cellular network instead of a mile of buried cable.

Or it speaks Modbus, when the job is many readings rather than one loop. More on that below.

Both paths are engineered to your site. Which input, what range, how it is scaled, where the panel is, and what your integrator needs mapped are all questions we work through with you before anything is built.

Modbus, when one connection has to carry many readings

4-20 mA is one lane per sensor. It is perfect for restoring a specific signal or adding a couple of tanks, and it is terrible arithmetic when you need twenty new values and the panel has two channels left.

Modbus is the other path, and nearly every SCADA system already speaks it. Where 4-20 mA is one lane, Modbus is a numbered mailbox wall: one connection, many addressed values. Your SCADA polls the bridge the same way it polls any local device, and one input port becomes capacity for hundreds of readings instead of one. When your panel is full and the capital plan says “I/O expansion,” this is the line item that can replace it.

Most projects end up using both. The loop restores or extends the signals your logic already depends on. Modbus carries the wider set of readings you want on screen.

Scenario: a severed signal, and pumps back on manual

A buried control line fails the way buried things always fail: suddenly, invisibly, and somewhere along a length you cannot inspect. What the system loses is not just a number on a screen. It is the automation that ran on that number. Tank level stops arriving, so the fill pumps stop starting and stopping on their own, and an operator goes back to running them by hand and by eye.

We have watched this from the inside. Huntsville Town, Utah lost the wired signal from its million-gallon tank, a mile up a steep hill, when the line was cut. The quote to trench a replacement came in at $50,000 to $80,000. A wireless Meterra sensor put the tank level back on screen for a fraction of that, and that part is done and running.

The next step for that system is exactly what this page describes: bridging the wireless reading back into the town’s SCADA so the pumps can run on automation again instead of by hand. That work is proposed, not delivered. We are not going to write it up as a finished result until it is one.

If your situation looks like that, a dead input and automation running on human attention, this is the fix that does not involve a backhoe.

Scenario: finding where clean water gets into a sewer

Spring runoff has a way of finding cracks in a sanitary sewer line. The water that gets in is clean, but once it is in the pipe it is sewage as far as the treatment bill is concerned. Everyone involved knows it is happening. What nobody knows is where, and you cannot dig up a whole line to find out.

Meterra answers that question by measurement: wireless ultrasonic sensors at multiple points along the line, a dry-season baseline recorded first, then the same points compared during runoff. Those readings can land on the Meterra dashboard, in your existing SCADA through the bridge described above, or in both.

That method has its own page, including where our mountain-resort sewer project actually stands today, stated plainly: Sewer Inflow & Infiltration Monitoring.

This isn’t theoretical. On the Powder Mountain job in Eden, Utah, a pond level sensor on a 15 ft cable has been reporting from an evaporative sewer pond into the community’s legacy SCADA since July 15, 2026, completely wireless:

Where else this fits

The same setup works anywhere dirtier water needs to be measured for flow or level: storm drains, sanitary sewer lines, lift stations, lagoons, and treatment basins. Non-contact ultrasonic reads the surface from above, so nothing sits in the flow to foul or corrode, and the reading can go to a control system, to the Meterra dashboard, or to both.

For clean water inside a pipe, surface level is the wrong measurement, so we do not use this approach. That job belongs to the Water Flow Monitor, an in-line turbine meter that reports gallons used every hour. Chemical and dosing tanks are covered on Chemical & Dosing Tank Monitoring, and they can feed the same bridge.

What it costs, and why this one is quoted

The sensors this runs on have their prices printed on the page. The bridge does not, and we would rather explain that exception than hide it.

The level sensors are posted. The Tank Level Sensor is $299, the Trough Level Monitor is $399, and the Dam Level Monitor is $499, reading open water to about 330 ft. Each includes three months of connectivity, then plans run from $10/month per device. Every sensor carries a 60-day money-back guarantee and a one-year warranty, and tank sensors ship from US stock in 1 to 2 business days.

The bridge is quoted per site, and here is why. It is engineered to your system, not pulled off a shelf: which input it feeds, how that input is scaled, where the panel sits, how many readings you need and over which path, what your integrator has to map, and whether cellular reaches the sensor locations. That is a scoped project. You get the number in writing before anything is built. What you will never get from us is a project priced like a catalog part, or a catalog part priced like a project.

The number worth putting ours next to is the alternative you are probably already holding: a trenching and I/O quote, or a proposal to replace a control system that is doing its job fine. Get both totals in writing and compare them honestly. We are comfortable with how that comparison usually ends, which is why we are telling you to run it.

What changes on your side

Less than you would think, and we will not pretend it is nothing.

Your SCADA vendor or integrator maps what arrives, whether that means confirming the scaling on a restored 4-20 mA loop or telling the system that a given Modbus register is the hilltop tank level. That is a configuration change, parameters rather than construction, and we coordinate it with them directly rather than leaving you in the middle. Every project starts with a conversation about what you run, what the panel looks like, and whether cellular coverage reaches your sites, before anything is quoted or shipped.

One boundary, stated plainly: this supplies monitoring inputs to your system. Control decisions stay in your SCADA, under your operators, exactly as they are now.

Tell us what you run

If your input panel is full, a signal line is down, or a rewire is sitting on the capital plan, that is worth a phone call before it is worth a backhoe.

Call (385) 534-8200 and describe the panel and the sites you need to see, or send the details and request a quote and we will come back with what the bridge would take on your system. If the field sensor is the piece you already know you need, the Tank Level Sensor at $299 is usually the one that ends up on the tank.

Meterra has been putting sensors in the field for over four years, with 2,000+ devices in service across a twelve-product ecosystem. Old control systems and new sensors get along better than most people are told.