In addition to converting sensor signals, electronics also optimize them. There will always be factors, however miniscule, that affect a sensor’s performance. In real-world applications, strain gauge-based sensors are often exposed to conditions and environments that may induce signal noise. The systems themselves can also present challenges: the more components that are added to a measuring solution, the more errors will be introduced. Electronics can help solve sensor challenges and optimize the signal by amplifying, filtering, protecting, and compensating the output. As technological advances require ever-more complex and precise measurement systems, sensors have become increasingly dependent on electronics, to the point that sensors are now used with electronics in nearly all applications.

FUTEK’s electronics (signal conditioners/amplifiers) are compatible with any kind of strain gauge–based sensor. This includes load cells (aka force sensors), torque sensors, multi-axis sensors, and pressure sensors.

Excitation Voltage: Full-bridge load cells require an excitation voltage from the Wheatstone bridge amplifier to feed the strain gauge bridge and generate its output signal as a ratio of the input excitation voltage. Thus, you need to establish if your DAQ or PLC can support the sensor’s input voltage or excitation voltage requirements. If you need a load cell amplifier for PLC or DAQ and they do not provide a stable input excitation voltage, the amplifier will be the excitation voltage source to ensure that the sensor provides a reliable and consistent output signal. For example, FUTEK’s USB Load Cell Data Acquisition System can provide excitation for amplified sensors up to 24VDC.

Filtering: Filtering is extremely important as it helps produce a clean and usable output signal. Analog sensor signals are susceptible to electrical noise and/or residual ripple voltage, which can distort or skew measurements. Hence, noise needs to be filtered out before you can capture an accurate signal. Electronic filters in a low noise load cell signal conditioner increase accuracy by removing electrical noise and ripple effect above and below the analog sensor’s signal range, resulting in a low signal-to-noise ratio. For example, FUTEK IAA series analog signal conditioners have bandwidth selection features that are used to set the bandwidth from 100 Hz to 50,000 Hz, allowing for noise filtering according to the load cell application.

Amplification: A full-bridge strain gauge sensor can output a signal in the nanovolt through millivolt range. When your DAQ or PLC is limited to measuring volts, you will need a strain gauge amplifier to convert millivolts to a larger signal. Some PLCs and DAQs come with built-in amplification; others will require an external amplifier. For multi-axis sensors, such as a 6 DoF Force Torque sensor, you need a multi-channel load cell amplifier circuit with the capability to process all the mV/V outputs of the channels.

Signal conversion: The majority of strain gauge-based sensors (or transducers) generate an analog output in the millivolt range (mV/V). Thus, signal processing is traditionally analog. So, if your PLC or DAQ system requires an amplified analog (i.e.: mA analog current, VDC analog voltage) or a digital output (USB, SPI, UART), the load cell needs a strain gauge signal conditioner to convert the mV/V signal to the required signal output. Normally, a load cell display or a load cell indicator is required for local indication (load cell readout) of the force measurement value.

Some applications require digital output, which will require a signal conditioner with an analog-to-digital converter (ADC).

Besides boosting and optimizing the strain gauge signal in the steps above, signal conditioners/amplifiers also play an important role in mitigating external factors that can affect the sensor output. All sensors, no matter how well-designed and precise they may be, will encounter challenges that affect their performance. Using a high-quality signal conditioner/amplifier minimizes these imperfections and optimizes the sensor’s output. Below are some common challenges that can be mitigated with electronics:

Excitation: Strain gauge-based sensors require an external power supply (excitation) to operate. In other words, the excitation signal is used by the sensor to produce the output signal. As we showed above in our breakdown of the Wheatstone bridge circuit, the output of the bridge is derived directly from the input to the bridge. This means that the quality of the sensor’s output is directly related to the quality of the input (excitation) and that to achieve a clean output, an equally clean input (excitation) must be provided Hence, it’s critical to properly design the excitation circuitry to provide a clean, low drift and well-regulated output and stable excitation signal.

Sensitivity Error: The slope of the characteristic output curve of a sensor usually defines the sensor’s sensitivity. Hence, the amount of deviation from the ideal curve defines the sensitivity error, which could result in the sensor being non-symmetric and also directly impacting the dynamic range (the total range, from minimum to maximum, that could be measured during normal operation). For example, an ideal sensor does not have sensitivity error thus, it is fully symmetrical. However, in practice, the output of a real sensor could deviate up to 20% (sometimes even more) from each direction. In order to minimize the error, this deviation needs to be addressed by the electronics connected to the sensor.

Precision: The degree of reproducibility of a measurement is defined as precision. This means that an ideal sensor would be able to measure the same exact value over and over with the same stimuli. In practice, the output of a real sensor could be impacted by external factors that we cannot fully control, such as the nature of the material that the sensors are made from, or some processes that the sensors need to go through during manufacturing. This shows the importance of keeping the errors introduced by the electronics being at least one order of magnitude lower than errors introduced by the sensor. At FUTEK, we have invested a lot of time investigating and analyzing our manufacturing process to identify these errors, finding a solution for every step in the process, and addressing them in our electronics design process as well. The same concept is valid for the accuracy characteristic of the sensor.

Sensor Resolution: The definition of resolution can be expressed as the smallest detectable change of the input that can be presented in the output. It means that the electronics must be designed to have a higher level of precision that is capable of resolving the output of the sensor to provide a precise measurement.

Offset Error: As we have already established, there is no perfect or ideal sensor, which means that some errors are expected for the sensor output. In other words, the offset error of a sensor is defined as the output that exists when there is no load. FUTEK minimizes the offset error of the sensors during the manufacturing process, but this error cannot be eliminated 100%, which is why electronics are needed to limit its effects.

Linearity Error: The linearity of the sensor could be identified as how much the actual measured output curve of a sensor could deviate from its ideal straight-line curve. Amplifier/signal conditioners will also have some linearity errors, so it is important to consider designing a circuit that provides extremely low error in comparison to the sensor error. This makes sure that the overall system non-linearity remains close to the sensor error. It should be mentioned that in some extreme cases, the electronics are designed to provide linearization. This approach usually involves a lot of complications, such as additional digital/firmware development and enhanced calibration that need to be implemented on the electronics side by understanding the unique nonlinearity characteristic error of every sensor.

There are other factors related to the sensor specs that electronics can help mitigate, such as Hysteresis, Response Time, Bridge Resistance, Sensor Drift, etc. To learn more about these terms, please see FUTEK’s glossary.

Sensors and signal conditioners talk to each other through signals that are transmitted via a device-to-device communication protocol. Below is a breakdown of the different types of output:

What is analog voltage?

An analog voltage signal is an electrical signal that varies in voltage and is measured in volts. Voltage signals represent and transmit continuous analog data and are typically used in low-power applications.

What is analog current?

An analog current signal refers to an electrical signal that varies in current and is measured in amperes. Current signals represent and transmit continuous data and are typically used in high-power applications.

Digital USB

USB supports and digitizes a wide range of sensor inputs such as ± 10 VDC, 0-30 mA, ±400 mV/V type inputs using an integrated analog to digital converter (ADC). USB output is particularly well suited for test and measurement applications that require dynamic force capturing and processing. FUTEK’s Pro Elite High Resolution and Speed USB Output Kit is ideal for these applications as it offers high-speed signal sampling (up to 38,400 SPS) and advanced filtering capabilities, ensuring precise capture of interaction forces and enabling detailed analysis of force measurement for validation and verification.

What is digital UART?

UART (Universal Asynchronous Receiver Transmitter) is a widely-used serial communication protocol in embedded systems. It is known for its simplicity and ease of operation and transmits data one bit at a time sequentially over a communication channel. Common serial communication protocols include RS-232, RS-485, USB (Universal Serial Bus), and SATA (Serial ATA). FUTEK’s Digital Jr S-Beam Load Cell 3.0. is a smart sensor with embedded electronics and data flexibility that is available in two versions: one that offers UART communication and another that offers both SPI and UART connectivity.

What is digital SPI?

SPI (Serial Peripheral Interface) is another serial communication protocol that facilitates data exchange between various electronic devices supporting clocked serial streams. It is known for its simplicity and ease of operation. SPI follows a Host-Client communication approach, allowing high-speed data transfer. It is known for its efficiency and low overhead, making it ideal for high-speed data transfer in applications like load cell signal conditioning.

Meet FUTEK’s flagship amplifiers/signal conditioners

The kind of electronics you select depends on the setup and requirements of your application. There are many types of amplifiers or signal conditioners, ranging from analog to digital solutions, panel displays to micro-mini embedded units. FUTEK’s electronic systems have been designed and manufactured to achieve a next-level performance that is a level above conventional measurement industry solutions. Some of our most well-regarded models are featured below:

IAA100/IAA200 Analog Current and Voltage Amplifiers

The IAA models combine unsurpassed accuracy with ease of integration. The units offer in-line amplification of any full bridge strain gauge type sensor with mV/V range output force measurement systems that demand voltage or current output. The IAA Family provides bridge excitation of either 5 or 10 VDC (DIP Switch) and amplifies strain gage sensors output ranges from 0.5 mV/V up to 10.0 mv/V (DIP Switch). Bandwidth ranges between 25 to 50 kHz. The units feature an integrated DIN clip designed for applications in industrial environments.

IHH Digital Hand Held Display

The IHH500 is a battery-operated handheld display and sensor indicator that connects to a computer via USB. It’s suitable for strain-gauge-based load cells, torque sensors, and pressure sensors in engineering applications. This digital weight indicator features an integrated low noise/high-speed/high-resolution ADC, accommodating various sensor inputs. Available in Pro and Elite versions. The versions share the same capabilities, and the Elite also reads and records encoder data like angle and speed. It also includes SENSIT® software for live graph data logging.

The IPM650 Panel Mount Display

This panel mount display, also known as a load cell readout, is an all-in-one standalone solution with a super-fast sampling rate and high resolution.The versatile multi-function display provides seamless integration with USB (2.0) connectivity and supports a wide range of sensor inputs, accommodating up to ±500 mV/V Strain Gauge, ±12 VDC, or 0-30 mA load cells, torque, and pressure sensors. The panel mount design ensures secure integration into your control systems, maximizing sensor/ transducer performance to lower noise and improve precision.

IAA105 Digitally Configurable Analog Voltage Amplifier

IAA105 is a one-of-a-kind amplifier that breaks new ground in sensor electronics. The fully digitally configurable device (offset/span (VDC) of –10 to +10) offers unsurpassed flexibility and simplicity during setup. This highly accurate device also features Bluetooth® wireless communication and USB configurability as well as built-in active protection for exceptional reliability and robustness. Its uniquely precise system calibration can go as low as 300μV. It has the lowest noise (2.8 mVp-p) of FUTEK’s high precision analog solutions and will push the performance of any sensor to its maximum potential.

USB225 High Resolution & Speed USB Output Kit

Some applications require digital output, which calls for a signal conditioner with an analog-to-digital converter (ADC). FUTEK’s groundbreaking USB amplifiers offer a modern, single-unit turn-key solution that eliminates the need for external circuitry and power supply. When selecting the digital amplifier for those applications, two critical parameters must be taken into consideration: noise-free resolution and sampling rate. FUTEK’s innovative digital strain gauge signal conditioner USB225 has exceptionally high resolution (up to 20 bits) and a sampling rate (max SPS 38,400) that has been pushed beyond traditional limits. The unit also has unique features and capabilities such as innovative fault detection and health checks.

The easy plug-and-play connection eliminates the need for external circuitry and power supply. Risk for failure has been minimized through fault detection features that continuously monitor the sensor’s health and indicate any issues, providing crucial feedback for applications that need to be fail-proof.

QIA128 Ultra-Low-Power Miniaturized Integrable Sampling System

QIA128 is a miniature embedded sampling system for load cells with ultra-low power consumption of only 60 mW. It is capable of sampling strain gauge signals up to 1300 samples per second (SPS) with up to 18.4 Bits of Noise Free Resolution (NFR).

It is compatible with strain gauge bridge resistance ranging from 350 Ω to 5000 Ω. This miniaturized integrable sampling system comes in an ultra small package of 8 mm x 8 mm, which makes it ideal for medical devices or robotics applications where assembly space is a limiting design factor.