Weight transmitters for load cells and force transducers

Weight transmitters for load cells and force transducers convert the mV/V signal of a load cell or force transducer into a format your control system can work with: 4…20 mA, 0…10 V, Modbus RTU via RS485, PROFINET, EtherCAT or IO-Link. Versions for DIN rail mounting, single- and multi-channel, with relay outputs for dosing and filling processes. Our range also includes models with PL (Performance Level) and SIL (Safety Integrity Level) approval. Price, data sheet and CAD model are online for every item.

Choosing weight transmitters for load cells and force transducers

Transmitter, indicator or measuring amplifier?

All three types of device connect to the same load cell, but they serve different purposes. The terms are used interchangeably on the market, so here is the distinction as we use it in the shop:

A weight transmitter, also called a signal converter or weighing amplifier, sits on the DIN rail in the control cabinet and has one job: getting the weight into the control system. The small display is for commissioning and diagnostics, not for the operator. It is the right choice when the plant evaluates the scale automatically.

A weighing indicator is built for people: large display, keypad, housing or panel mounting, functions such as tare, totalizing and ticket printing. You need one when someone has to read the value and operate the device.

A strain gauge amplifier is designed for measurement engineering, not for weighing: high bandwidth, several channels, data logging. The choice for test rigs and laboratories, where the force curve matters rather than the final value.

Which interface suits your control system?

Analog, 4…20 mA or 0…10 V, is the simplest solution if the PLC has a free analog card and only one value has to be transmitted. Keep in mind that the actual resolution is determined by your input card, not by the transmitter. A 16-bit output is of no use if it meets a 12-bit input. For noise immunity over longer cables, 4…20 mA is preferable to the voltage version.

Modbus RTU via RS485 uses no analog input and transmits more than just the weight: status, raw signal, tare values, error messages – and you can trigger zeroing and taring from the control system. A bus also lets you run many devices on one line, which considerably reduces wiring when there are several weighing points.

PROFINET and EtherCAT are the obvious choice if your plant already runs on that fieldbus. You get cyclic data at a defined update rate and diagnostics in your usual engineering tool. Details of the supported protocols can be found on our page on fieldbuses.

IO-Link is the low-cost digital option at sensor level: device-level parameterization, tool changes without readjustment and no analog wiring. It makes sense for simple weighing points and wherever you connect many similar points. More on this under IO-Link.

Speed and filters

The update rate decides whether a transmitter is suitable for your process. For a vessel level display, a few measurements per second are enough. For dosing, filling with in-flight correction or checkweighing in cycle, you need short response times, otherwise your control switches off too late.

The relationship is inconvenient but unavoidable: filters steady the display and cost response time. With oscillating loads, agitators and vibration you will have to filter, and the cut-off threshold then needs more lead time. Devices with an adjustable filter stage and several selectable rates give you room to maneuver during commissioning.

One channel or several?

For a weighing point with several cells, the signals are traditionally combined in a junction box and evaluated by a single-channel transmitter. This is the least expensive option and the right one for most tank and platform scales.

A multi-channel device reads each cell individually. The advantage shows in operation: you can see which cell is drifting or defective, adjust the corner load deviation electronically instead of mechanically, and see on silos whether the load is unevenly distributed. With several separate weighing points in one plant, you also save devices and cabinet space.

Commissioning

There are two routes to a calibrated scale. Theoretical calibration uses the rated load and the sensitivity in mV/V of the cells from the data sheet, and the device calculates the scaling from these. A weighing point is ready for operation in minutes without test weights, which for large silos is often the only practical option. Real calibration with test weights is more accurate because it takes installation effects into account, and it is required for legal-for-trade applications anyway.

If the plant is to be operated as legal for trade, the evaluation electronics must be suitable for this as well, not just the load cell. Talk this through with us before you choose. For the cells themselves, we calibrate to ISO 17025 in our own laboratory.

Other functions that count in the process

Relay outputs with adjustable setpoints handle coarse and fine flow during dosing, or the overload alarm, without the PLC having to intervene. Digital inputs take over zeroing and taring from an operator panel. For reading from a distance, combine the transmitter with a large display; for mobile use there are wireless systems and handheld devices.

You will find the matching sensors under load cells and force transducers, and the rest of the range under measuring electronics. Our engineers will advise you directly on choosing the interface, number of channels and sampling rate.