Indicators & displays

Digital indicators and displays for industrial measurement and process variables

Digital indicators and process displays make electrical sensor signals directly visible as easy-to-understand measured values. They acquire analogue signals such as 0–10 V or 4–20 mA, scale them to the required physical quantity and clearly display the measured value on an LED or LCD display.

Althen digital indicators are suitable for a wide range of industrial measurement tasks. Depending on the device, they can process not only standard industrial signals but also DC voltage, DC current, resistance, thermocouples, Pt100 or signals from strain gauge-based sensors. This allows force, pressure, temperature, displacement and other process variables to be displayed directly in the required unit.

The devices offer much more than simple measurement display. Functions such as free scaling, linearisation, minimum and maximum value storage, totalisation and limit monitoring allow flexible adaptation to the respective application. With dual-channel devices, measured values can also be mathematically combined.

Optional output and interface modules allow measured values to be transmitted to control systems and higher-level systems. Depending on the version, analogue outputs, relay or transistor outputs as well as serial or industrial communication interfaces are available.

With rugged front panels rated up to IP65 and compact housings for panel mounting, the indicators are suitable for machines and production systems as well as test benches and laboratory applications.

Flexible display, monitoring and further processing of measured values

Althen digital indicators combine versatile signal inputs with flexible scaling and extensive monitoring functions. This allows a wide variety of sensor and process signals to be displayed directly in a meaningful physical unit.

What to consider when selecting a digital indicator

1. Determine the input signal
The most important selection criterion is the signal to be displayed. Industrial sensors and transmitters provide, for example:

• 0–10 V
• 0/4–20 mA
• DC voltage or DC current signals
• Resistance signals
• Thermocouple signals
• Pt100 signals
• Strain gauge or mV signals

The digital indicator must have a suitable input for the respective signal.

2. Consider the sensor or transmitter
For sensors with an integrated measuring amplifier, an indicator for a standardised 0–10 V or 4–20 mA output signal is often sufficient.

Other sensors require specially designed input electronics. Universal indicators for thermocouples and Pt100 are available for temperature measurements, for example. For strain gauge-based transducers, devices with an integrated strain gauge input and corresponding sensor excitation can be used.

3. Select a single- or dual-channel indicator
For most applications, a single-channel digital indicator is sufficient. If two measured variables need to be acquired simultaneously or mathematically combined, a dual-channel indicator may be useful.

The PAX-DP, for example, can acquire two galvanically isolated current or voltage signals and mathematically combine them.

4. Consider display type and readability
LED displays provide high-contrast measurement values that are easy to read even from a greater distance.

Multi-line LCD displays can also show additional information simultaneously. For example, the process value, total value, alarm value or physical unit can be displayed at the same time.

On certain devices, the display colour can also change depending on the operating or alarm status.

5. Scale the measured value to the physical quantity
A sensor signal is usually intended to be displayed not as an electrical value, but as the actual measured quantity.

For example, a 4–20 mA signal from a pressure sensor can be scaled to a display range of 0 to 100 bar. Programmable digital indicators allow a freely definable relationship between the input signal and the required display value.

6. Consider linearisation
Not every measured quantity behaves perfectly linearly across the entire measuring range. Multi-point linearisation makes it possible to correct such deviations electronically.

Various indicators in the PAX series offer linearisation with up to 16 steps.

7. Define the required monitoring functions
In addition to the current measured value, further functions can be used depending on the device, for example:

• Minimum value
• Maximum value
• Total value
• Tare
• Integration over time
• Alarm and limit values

This allows the indicator to perform additional process monitoring tasks.

8. Consider limit values and switching outputs
If an action is to be triggered when a measured value exceeds or falls below a defined threshold, optional relay or transistor outputs can be used.

These can be used, for example, to control warning lights, acoustic signals or inputs of a machine control system.

For safety-critical shutdown functions, however, it should always be checked which additional independent safety functions are required.

9. Check whether an analogue output is required for further processing
If the displayed measured value also needs to be transmitted to another device, an additional analogue output can be useful.

Depending on the configuration, the scaled measured value can, for example, be output again as a 0/4–20 mA or 0–10 V signal.

10. Consider digital interfaces
Optional communication interfaces are available for various indicators for integration into higher-level systems.

Depending on the device or option card, these include, for example:

• RS232
• RS485
• Modbus
• DeviceNet
• PROFIBUS DP
• USB

This means measured values can not only be displayed locally, but also transmitted to PLCs, PCs or other automation systems.

11. Consider protection rating and installation situation
The indicators are designed for installation in control panels and operator panels. For industrial applications, the protection rating of the front panel is particularly relevant.

Depending on the model, PAX indicators feature an IP65-rated front panel and are therefore suitable for many industrial environments.

12. Check the supply voltage
Different supply variants are available depending on the version. Some devices feature particularly wide-range AC/DC power supplies, allowing flexible integration into different machine and system concepts.

Our technical expert team will be happy to support you in selecting the input signal, display, scaling, output functions and interfaces for your application. Contact our sales team

Typical applications for digital indicators and displays

Digital process indicators are used wherever sensor signals need to be made visible directly on site, monitored or processed for further control tasks.

Typical applications include:

• Machine and plant engineering
• Industrial process monitoring
• Automation technology
• Control panel and operator panel installation
• Force and load indication
• Pressure indication
• Temperature indication
• Displacement and position measurement
• Level monitoring
• Flow measurement
• Weighing technology
• Test benches and test systems
• Quality control
• Production monitoring
• Limit monitoring
• Laboratory and testing applications
• Research and development

Thanks to different input signals and expansion options, the indicators can be flexibly combined with sensors, transmitters and higher-level control systems.