Every load cell produces an electrical signal that changes when a load is applied. What that signal looks like when it reaches your PLC, indicator, or data logger is what we call load cell output, and it comes in three common forms: raw mV/V, a 4-20 mA current loop, or a 0-10 V voltage signal.
mV/V is the unamplified signal straight from the strain gauge bridge. It is the most accurate at the source but needs a conditioner or indicator before a controller can use it.
4-20 mA is an amplified current signal that shrugs off electrical noise, travels long distances, and is mostly used in PLCs.
0-10 V is an amplified voltage signal that is easy to read on standard controllers but prefers short cable runs.
In this article, we walk through how each output works, where it fits, and how to pick the right one for your installation.
What “Load Cell Output” Actually Means
A load cell does not measure weight directly. It measures strain. Strain gauges bonded inside the cell stretch or compress by a tiny amount when a load is applied, and that movement changes their electrical resistance. The cell turns that resistance change into a small voltage on its signal wires, typically just a few millivolts at full capacity.
That millivolt signal is the load cell’s output in its purest form. It is what the sensor itself produces, but it is far too small for a PLC or controller to read on its own.
Because of that, every practical weighing system adds a piece of electronics between the cell and the controller. That device amplifies the signal, filters out noise, and scales it into something the controller understands.
If the term mV/V is new to you, start with our introductory guide to mV/V. It covers sensitivity ratings, the mV/V calculation, and typical values by application. This article picks up where that one leaves off.
mV/V: The Raw Signal
It’s the direct output of the load cell strain gauge bridge, expressed as millivolts per volt. A 2 mV/V load cell with an excitation voltage of 10 V gives roughly 20 mV output at rated capacity.
How it’s used: The signal output goes over a four- or six-wire cable to an indicator calibrated to display the weight or load applied, or it goes to a signal conditioner calibrated to send the Analog signal to the controller or PLC.
Six-wire cables are a good idea, especially for longer distances between the load cell and indicator. They add sense lines that let the instrument account for voltage drop along the cable, which is why you’ll see it show up on longer runs and outside installs.
Where it does best:
- Accuracy at the source: No extra electronics that can influence the accuracy
- Simplicity and durability: Load cells typically have a longer service life compared to indicators
- Multi-cell systems: Truck scales, tank systems, and floor scales can sum several mV/V cells in a junction box before a single instrument reads the result. That summing only works with matched raw signals, which is one reason mV/V is still the default for legal-for-trade weighing.
- Cost: A mV/V cell is the most cost-effective option when you already have an indicator or weigh module on the receiving end.
Where it struggles:
- Noise: A 20 mV full-scale signal is tiny. Run it alongside a VFD or a big motor without proper shielded load cell cables and grounding, and you’ll see it in your readings.
- Not PLC-ready: A standard PLC analog input card is looking for volts or milliamps, not millivolts. You need a conditioner, transmitter, or dedicated weigh module in between.
- Cable length: Longer runs mean more resistance and more opportunity for interference. Six-wire cables help, but at some point, converting to an amplified signal is the cleaner solution.
4-20 mA: The Current Loop
It’s an amplified analog current signal where 4 mA represents zero load and 20 mA represents full capacity. Anything in between is proportional to the applied load.
How it’s used: A signal conditioner or transmitter takes the mV/V signal, amplifies it, and drives a current through a loop that the PLC or controller measures.
Massload’s ML 4-20MA Signal Conditioner is a good example: it’s small enough to mount inside the load cell housing or a nearby enclosure, runs on a 9 to 30 VDC supply, and outputs a standard two-wire 4-20 mA loop straight to the PLC.
Where it shines:
- Noise immunity: Current is not affected by induced voltage the way a voltage signal is. That makes 4-20 mA the go-to choice around motors, drives, welders, and long cable trays.
- Covering long distances: Because the loop carries current rather than voltage the cable’s resistance doesn’t affect the reading, which is just what you want when the load cell is all the way out at the other end of the control room.
- Fault detection built in: In some transmitters, there is an alarm function that provides the status of the scale or load cell. Depending on the status, it can send a constant mA, for example 0 mA or 22 mA, which is outside its normal range. This then tells the controller something wrong is going on.
- Simple and straightforward two-wire or three-wire setup: Flexibility to choose between a two-wire or three-wire 4-20mA to match the input requirement of the indicators or PLC or other controllers.
Where it struggles:
- Needs more hardware: You’re going to need the conditioner, a reliable DC supply, and a controller input that’ll accept the current signal.
- Resolution ceiling: The amplifier and the PLC’s analog-to-digital converter define your resolution, not the load cell.
0-10 V: The Amplified Voltage Signal
It’s an amplified analog voltage where 0 V represents zero load and 10 V represents full capacity.
How it’s used: a conditioner or transmitter scales the raw signal into the 0–10 V range. Most PLC analog cards, data acquisition modules, and building automation controllers accept it natively, and many signal conditioners offer both 4–20 mA and 0–10 V outputs on the same unit so you can pick whichever your controller prefers.
Where it shines:
- Easy to interface and troubleshoot: A simple volt meter across the output will tell you exactly what the controller is seeing.
- Broad compatibility: Voltage inputs are common on lower-cost controllers, data loggers, and lab equipment.
- Fast response: Voltage outputs can be very quick, which suits dynamic applications like check weighing and force testing.
Where it struggles:
- Cable length: Every foot of cable adds a bit of resistance, and resistance drops the voltage. Over long runs, the controller will see a slightly lower voltage than the conditioner sent, which reduces the resolution.
- Noise and ground loops: Voltage signals are more prone to picking up interference than current signals – and they’re sensitive to ground potential differences between the sensor and the panel as well.
How To Choose the Right Load Cell Output
Work through these questions in order, and the answer usually falls out on its own.
1. Is the application legal-for-trade or multi-cell?
If you are building a truck scale, floor scale, or vessel system with several cells, stay with mV/V and sum in a junction box.
Our guide to how many load cells you need explains why matching matters here. Convert to an analog output after the indicator if the PLC needs it.
2. What does your controller accept?
Many PLC analog cards handle both current and voltage, but check. If you have a dedicated weigh module or a load cell indicator with a serial output, you may not need an analog conversion at all.
3. How far is the cell from the panel, and what is in between?
Long distance, electrical noise, or an outdoor run all point to 4–20 mA. A short, quiet run inside a machine or a lab bench is where 0–10 V is perfectly reasonable.
4. Do you need to know when something breaks?
In unattended process control, batching, and overload protection, pick a 4-20mA with built-in alarm and threshold relay output.
Our crane overload protection article shows how these outputs feed set points and relays in practice.
5. What is the environment like?
Keeping the amplifier out of the cell and back at the panel (the mV/V approach) is often the more robust choice for extreme temperatures and washdown. When the conditioner must live at the sensor, choose one rated for the conditions.
Beyond Analog: Digital And Wireless Outputs
The three analog options cover most of the bases, but there are two more options worth knowing about.
Digital outputs such as RS485 Modbus, Ethernet/IP, Modbus TCP or PROFINET come from load cell transmitters that convert the mV/V signal and send weight as data, not as a proportional current or voltage. They let you have several transmitters on one cable, carry diagnostics alongside the weight value, and get rid of analog scaling errors altogether.
Wireless outputs get rid of the signal cable altogether. They’re good for rigging, rotating equipment, and places where running a cable just isn’t practical or safe.
Get The Right Load Cell Output For Your System
Massload’s standard or custom load cells come as mV/V sensors right out of the box and from there are all sorts of instrumentation options to choose from: signal conditioners for 4–20 mA and 0–10 V, transmitters with analog and fieldbus outputs, indicators, and wireless systems for the hard-to-cable jobs.
If you’re not sure which output will fit your application, talk to our team. We have been curating standard products for these applications for over 40 years now.
