Strain gauge amplifiers

Strain gauge measuring amplifiers for precise sensor signals

Strain gauge measuring amplifiers – also known as strain gauge amplifiers or strain gauge signal conditioners – are used for the precise evaluation of sensors and transducers based on strain gauges. These include load cells, force transducers, pressure transducers and other strain gauge-based sensors.

Strain gauge sensors typically provide very small output signals in the millivolt-per-volt range (mV/V). A strain gauge measuring amplifier supplies the measuring bridge, amplifies the sensor signal and converts it into a robust output signal that can be processed by control systems, measuring instruments or data acquisition systems.

Althen strain gauge measuring amplifiers are available with various standard analogue outputs such as 0–10 V, ±10 V or 4–20 mA. Selected versions also offer USB data transmission, digital displays, limit contacts or additional functions for industrial process monitoring.

The portfolio includes compact inline measuring amplifiers, DIN rail-mounted devices, rugged IP65 versions for industrial environments, 19-inch rack modules and portable measuring and display devices. This allows the signal conditioning system to be optimally adapted to the installation situation, measurement task and environmental conditions.

Precise signal conditioning for a wide range of strain gauge applications

Althen strain gauge measuring amplifiers combine reliable bridge excitation with precise amplification and flexible output signals. Different designs and configuration options enable applications ranging from simple single-channel measuring points to industrial multi-channel systems.

What to consider when selecting a strain gauge measuring amplifier

1. Determine the output signal of the strain gauge sensor
Strain gauge-based sensors usually provide a signal in mV/V. When selecting the amplifier, the rated sensitivity and maximum expected signal range of the sensor must be taken into account. Typical strain gauge sensors, for example, have sensitivities of 1, 2 or 3 mV/V.

2. Consider bridge resistance and sensor type
The measuring amplifier must be electrically compatible with the connected sensor. Many Althen strain gauge measuring amplifiers are designed for strain gauge full bridges with a bridge resistance above 300 Ω. Other devices also support different bridge resistance values.

If individually applied strain gauges are used instead of a sensor already configured as a full bridge, it must be checked whether additional bridge completion is required.

3. Select the appropriate output signal
The output signal of the measuring amplifier should match the downstream control or evaluation electronics.

Typical output signals include:

• 0–10 V
• ±10 V
• 4–20 mA
• Digital data transmission via USB

Voltage outputs are particularly suitable for short to medium transmission distances and dynamic measurements. A 4–20 mA current signal offers advantages for longer cable runs and industrial installations.

4. Determine the number of measuring channels
Compact single-channel amplifiers are available for individual sensors. If several measured variables need to be recorded simultaneously, dual-channel or multi-channel solutions can be used.

Selected models also allow several strain gauge transducers to be operated in parallel on a common measuring channel.

5. Consider measuring speed and cut-off frequency
For static or slowly changing measured variables, a relatively low bandwidth is sufficient. Dynamic force, pressure or load measurements, however, require a higher cut-off frequency.

Different filter and bandwidth options are available depending on the amplifier. Selected industrial strain gauge measuring amplifiers provide cut-off frequencies of up to 30 kHz.

6. Choose between 4-wire and 6-wire technology
For short and constant sensor cables, conventional 4-wire technology is often sufficient. For long cables or varying cable lengths, 6-wire technology offers advantages because voltage losses in the sensor cable can be compensated.

Various Althen strain gauge measuring amplifiers therefore support both 4-wire and 6-wire connections.

7. Consider galvanic isolation
Galvanic isolation between the power supply, measuring signal and output can help prevent ground loops and disruptive potential differences.

Especially in industrial installations, with longer cable runs or several interconnected measuring systems, this can improve noise immunity.

8. Determine installation location and degree of protection
The optimal design depends on the intended installation location.

Compact DIN rail-mounted measuring amplifiers are available for control cabinets. Inline measuring amplifiers can be installed directly near the sensor. Rugged die-cast aluminium housings with protection ratings up to IP65 are available for harsh industrial environments.

For test benches and laboratory applications, 19-inch rack modules and benchtop devices are also available.

9. Check additional monitoring functions
In automated processes, it can be useful to monitor limit values directly within the measuring amplifier. Suitable devices provide adjustable limit contacts or relay outputs.

Additional functions may include summation or differential calculation of several measuring channels, tare functions, min./max. memory or a digital measured-value display.

10. Consider calibration and fine adjustment
To ensure that the sensor and measuring amplifier are optimally matched, zero point and gain must be adjustable or calibratable.

Many Althen measuring amplifiers therefore offer adjustment options for zero point and gain. Depending on the device, shunt calibration or additional digital calibration functions may also be available.

Our technical expert team will be happy to support you in selecting and matching the strain gauge sensor, bridge excitation, input sensitivity, bandwidth and output signal. Contact our sales team

Typical applications for strain gauge measuring amplifiers

Strain gauge measuring amplifiers are used wherever small bridge signals from strain gauge-based sensors need to be reliably conditioned and transferred to a control system, display or data acquisition system.

Typical applications include:

• Force measurement with strain gauge force transducers
• Load cells and industrial weighing technology
• Pressure measurement with strain gauge pressure transducers
• Torque and load measurements
• Test benches and test systems
• Machine and plant monitoring
• Process monitoring and process control
• Overload and limit monitoring
• Industrial automation
• Quality control
• Research and development
• Laboratory and testing applications
• Component and structural testing
• Mobile force and weight measurements
• Measurements with long sensor cables

Thanks to different output signals, bandwidths, channel configurations and housing designs, the measuring amplifiers can be used for both static measurements and dynamic measurement tasks.