Electronic Loads and Bespoke Test Equipment

Tester for Engine Control Unit

This system was designed to test engine control units for a major automotive component supplier. The picture shows the engine control unit with a set of electronic injector solenoids acting as loads on top, the interface unit simulating the input transducers, output loads and indicators and the cabling, with current transducers, connecting the two. The interface connects to analogue and digital control boards in an industrial computer. A test program, written in C++ under Windows®, controls the unit functionality. The program uses counter timers and dedicated hardware to simulate engine and wheel speed sensor outputs, digital outputs to simulate switches and digital to analogue converters to simulate linear transducers such as the throttle pedal, air pressure and temperature transducers. Front panel lamps give immediate visual indication of output states and BNC connectors are provided to allow various waveforms to be seen on an oscilloscope.

Tester for Smart Battery Chargers

We needed a method of production testing the fast lithium ion battery chargers that we had designed for a customer. The test method for the initial batch used two batteries in different stages of charge to fully check charger functionality. As we had to take one of the batteries over the charge termination point, then discharge it before testing the next charger, this was a time consuming business. A complete test system was designed and built to speed up the procedure.

Squarewave Generator

A customer had a problem finding a commercial generator that would produce a 250kHz squarewave generator capable of sourcing 28V peak-to-peak into 75 ohms to test terminated assemblies for burn-in tests. This bespoke solution fitted the bill. It has an internal crystal controlled oscillator to give the 250kHz output but, for other applications, an external low power oscillator can be used to provide an output from 100kHz to 1MHz. The dual channel output (10W each) was a useful feature to reduce total test time for the assemblies.

TRL Three-Phase Electronic Load

The power load is designed to calibrate the drag on a truck wheel. The equipment consists of a relatively small generator coupled to the wheel and the switched load. The rotational speed, and therefore the output voltage, is relatively low. This means that the current is proportionally high to get 1kW of load. The heat from the three phase load has to be dissipated and removed from the area near the wheel and control electronics. The load can be set to one third, two thirds or full power.

The picture below shows the load when it was calibrated for torque at a range of speeds and powers on a dynamometer rig. The large heatsink keeps the temperature of the unit at a safe level.

Electronic Load

Lambda UK needed a visual load to demonstrate their new Vega SmartPlus microprocessor controlled, four channel supply. Three channels each have an LED, a voltmeter and a fixed load. The fourth channel has an LED, a voltmeter, an ammeter and a variable load with switchable modes for resistive or constant current behaviour. The load will work up to 20V and 20A (even sinking this current down to 0.5V). It is electronically limited as a safety precaution to a continuous dissipation of 250W and will automatically reduce the load if the heatsink temperature rises too high in case the fan is blocked.