The KOBOLD AUF is a compact, loop-powered plug-on display that adds bright local LED indication to any transmitter with a 4-20 mA output and an EN 175301-803 Form A (old DIN 43650) connector, with no external power supply required for most models. It delivers one of the industry's simplest solutions for adding display capability to existing instrumentation, providing clear, reliable process visualization exactly where operators need it.
The AUF's compact sandwich construction installs in seconds between the existing connector and socket, without panel cutouts, conduit runs, or electrical permits. A 4-digit red LED display with 5/16 in digit height, two-key programming, and a housing that rotates in 90-degree steps make it suitable for pressure transducers, temperature transmitters, flow meters, and level sensors alike.
How the AUF Works Without External Power
The AUF is supplied by the current loop of the 4-20 mA signal transmitter itself, creating minimal system burden with a voltage drop of 5 V or less. According to specifications, only the pulse-input AUF-4000 requires an external 24 VDC ±20% supply; the other models need no auxiliary power.
Programmed parameters (scaling, decimal point position, damping, and optional switch point) are stored in non-volatile EEPROM memory that retains data after power loss for up to 10 years, eliminating reconfiguration after power interruptions. An integral diagnostic system continuously monitors device functions and reports out-of-range conditions directly on the display.
AUF Models for Every Application
Five models cover the full range of indication needs: the standard 2-wire AUF-1000; the AUF-1001, which adds a PNP open collector switch output; the ATEX/IECEx-certified AUF-2000 for hazardous areas; the 3-wire AUF-3000 for systems with separate signal and power loops; and the pulse-input AUF-4000 with 4-20 mA output.
The AUF-1001's optional open collector output (maximum current load 90 mA) adds alarm capability to basic transmitters without control system modifications, enabling local alarm indication and equipment shutdown capabilities directly at the measurement point. The AUF-4000 accepts pulse inputs from an NPN Hall effect sensor and converts them to a 4-20 mA output signal while displaying the process value; it can only be calibrated when factory-mounted with its sensor.
Certified for Hazardous Area Applications (AUF-2000)
The AUF-2000 carries ATEX approval II 2G Ex ib IIC T4 Gb and IECEx approval ib IIc T4 Gb, with conformance certificates BVS 17 ATEX E 022 and IECEx BVS 17.0012. This intrinsically safe version operates from -4°F to 104°F (-20°C to 40°C) and requires an intrinsically safe power supply barrier.
Entity parameters are Ui 28 VDC, Ii 100 mA, and Pi 0.9 W, with negligible effective inner capacitance and inductance, in a black polyamide housing with red PMMA window. These credentials enable safe pressure monitoring on offshore platforms, temperature indication in refineries, and level display in chemical storage facilities.
Installation and Programming
Installation requires disconnecting the existing DIN connector, inserting the AUF between connector and socket, then reconnecting which is typically completed in under 60 seconds. The included longer mounting screw ensures secure attachment while maintaining proper seal integrity, and the indicating unit rotates in 90-degree steps to match any installation orientation without rewiring.
Two push buttons, accessible after removing the four Phillips screws on the display cover, provide menu-driven adjustment of the zero point (4 mA value), span (20 mA value), decimal point placement, and damping from 0.3 to 20 seconds. For devices with NPT connections, an adapter (model 807.701) screws into an existing 1/2 in NPT opening and provides a Form A plug for the display.
Key Specifications
The AUF indicates from -1999 to 9999 with a programmable decimal point, achieves 0.2% of span ±1 digit accuracy, and updates 3 times per second. Performance designed for stable, reliable readings even in applications with process fluctuations. Temperature influence remains minimal at 0.15% per 18°F (10 K).
- Display: 4-digit red LED, 5/16 in digit height
- Voltage drop: ≤5 V (at maximum load 250 Ω)
- Protection rating: IP65
- Operating temperature: 32°F to 140°F (0°C to 60°C) standard models; -4°F to 104°F (-20°C to 40°C) AUF-2000; -4°F to 176°F (-20°C to 80°C) AUF-4000
- Storage temperature: -22°F to 176°F (-30°C to 80°C)
- Housing: orange PA6 GF30 plastic with red PMMA window (AUF-2000: black polyamide)
- Maximum current load: 60 mA
Typical Applications
Process engineers specify the AUF for pressure monitoring on hydraulic systems, temperature indication on heat exchangers, flow visualization on chemical dosing pumps, and level display on storage tanks. The universal 4-20 mA compatibility works seamlessly with pressure transducers, temperature transmitters, flow meters, and level sensors.
Unlike conventional panel displays requiring dedicated power supplies and mounting space, the AUF's plug-on design transforms installation from hours to minutes. Whether you need basic indication, alarm outputs, or hazardous-area certification, the AUF Series eliminates power supply installations and wiring complexity while giving operators critical process visibility.
Common Questions for Compact Local Electronic Display
The AUF is a universal local display for transmitters with a 4-20 mA analog output and an EN 175301-803 Form A (DIN 43650) plug connection. It mounts between the transmitter's connector and socket and shows the process value on a 4-digit red LED readout that can be scaled to any engineering unit.
Most AUF models take their operating power from the 4-20 mA measuring loop, consuming no more than 5 V of loop voltage. According to specifications, only the pulse-input AUF-4000 requires an external 24 VDC ±20% supply. This loop-powered design eliminates auxiliary power wiring at the measurement point.
The AUF works with any transmitter that provides a 4-20 mA analog output and connects via an EN 175301-803 Form A (old DIN 43650) plug. Typical pairings include pressure sensors, temperature sensors with head-mounted transmitters, turbine flow meters with analog output, and level transmitters.
Yes. The AUF-2000 is certified to ATEX II 2G Ex ib IIC T4 Gb and IECEx ib IIc T4 Gb (conformance BVS 17 ATEX E 022; IECEx BVS 17.0012). It must be used with an intrinsically safe power supply, verified against the entity parameters Ui 28 VDC, Ii 100 mA, and Pi 0.9 W.
Programming uses two keys, A and B, located behind the display cover. Key B steps through the menu items (decimal point (dP), zero point (ZP), span (EP20), damping (FILt), and range message) and pressing A and B together enters and confirms each setting. Values are retained in EEPROM after power loss.
Both are 2-wire, loop-powered displays for 4-20 mA signals. The AUF-1001 adds a PNP open collector switch output rated for a maximum current load of 90 mA, with an adjustable switching point and selectable switching direction, allowing local alarms without control system modifications.
Yes. An adapter (model 807.701) screws into an existing 1/2 in NPT opening and carries an EN 175301-803 Form A (old DIN 43650) plug on the opposite side, onto which the display plugs directly. Female cap plugs with a cable gland or with 1/2 in NPT conduit are also available.
The display indicates "HI" when the signal exceeds the upper range limit and "LO" when it falls below the lower limit; this message can be enabled or disabled in the HILO menu. With the message disabled, error code "Er06" appears if the scale range of -1999 to +9999 is exceeded.
Yes. The indicating unit rotates in 90-degree steps, so the readout adapts to different installation positions without rewiring. A dimension band can also be mounted beneath the LED display to label the engineering unit, and the housing carries an IP65 protection rating against dust and water ingress.