For many hydraulic test systems, the control (coil current) and output signal (control pressure) must be regulated very precisely and measured synchronously at a high frequency.

The requirement for a machine series for hydraulic pressure regulators, for example, was as follows: 12-14 parallel stations / number of measuring channels per station: 5 (coil current, supply pressure, control pressure, press-in force, oil temperature) / current control: 0..2..0A triangular function with superimposed sine wave of 167Hz / maximum measuring error 0.1% / number of measured values: 1000 per second per channel.

If you want to meet these requirements with commercially available systems, you have to combine several devices and controllers from different manufacturers and you need an additional large control cabinet for this measurement technology.

LIWO has accommodated the entire measurement technology for a station on two electronic cards, all of which can be accommodated in a standard rack for Europa cards.

These measuring cards have so far been used in over 15 machines at 9 different customers.

Here is an example of the cards (current driver and measuring card) and the entire rack in the system:

 For leak tests with a very high cycle rate, so-called continuous machines are often used. These high-speed rotary transfer machines often process 500 to 1000 parts per minute. In order to be able to carry out accurate leak tests with such short cycle times, many leak testers (30 to 80 units) or very complex technology is placed on the rotating tower.

In order to solve this task technically (especially space requirements and power consumption) and economically, LIWO has developed a leak tester that ultimately consists only of a basic board with additional possible plug-in boards. This module contains a microcontroller with memory and RAM, two power supplies, measuring amplifiers for sensor signals, communication modules to the PLC (CanOpen) and to the PC (via RS232), as well as interfaces for addressing and drivers for controlling the valves. In addition, there is a plug-on board that enables very fast and position-dependent real-time communication with the PLC via light signals. 

Many individual control components would normally be required for complex measurement technology to test the tightness and flow resistance of breathing lime filter cartridges.

The mechanical function diagram for a single station alone shows 11 valves, two pressure regulators, one flow regulator and several sensors for measuring pressure and flow:

A system with 6 stations of this type would have required an enormous amount of electronics, measurement technology and ultimately also software and administration, which is why LIWO decided to combine the aforementioned high-precision measurement technology with the self-sufficient testing technology and offer a measuring head in this combination that includes the complete mechanics, pneumatics, measurement technology, electronics and software.

The following picture shows the 6 LIWO measuring heads in a customer's system before the individual heads were each covered with a stainless steel hood. By having the measuring heads fully tested and supplied with certified software, LIWO saved the customer a lot of effort and also eliminated the need for a control cabinet that would otherwise have housed the measuring technology.

In the course of IoT and Industry 4.0, there are more and more applications that require very small controllers that can record, evaluate and store important measured values. Naturally, it is expected that these miniature devices can communicate universally and that their price is so low that they can be used everywhere and frequently.

Such requirements usually present machine builders with unsolvable problems, as commercially available components can rarely do everything that is needed in a specific case. One such list of requirements from a customer was: Maximum size 30x30x30mm / Battery operation possible / Measurement of voltage, current, acceleration and four temperatures / Data recording for each contacting process / Detection via current or acceleration / Display of all overload states (current, acceleration and temperatures) / Display of overall status via a parameterizable LED traffic light (red/yellow/green) / Specification of load-dependent maintenance intervals / Communication with PLC / Data transfer from and to PC / User administration and passwords / Comparison of sensor signals with entry in LOG data / Time stamp via built-in real-time clock / Possibility of real-time display of sensor signals on PC / Flexible expansion of both hardware and software functions.