Saturday, August 1, 2020 · 16 min read
Electric Household Appliance Testing
Today more and more household electrical appliances use microcomputers. Common household electrical appliances are now capable of doing some complex working procedures. BSH, a world-renowned manufacturer of household appliances needed a new test system to measure voltage, current, power, temperature, and more, to verify whether the work procedure of household appliances is consistent with the design or not.
The Dewesoft solution - a SIRIUS DAQ system, with a custom test box, flexible DSI sensor interface, and powerful DewesoftX data acquisition software - helped the customer get the test results needed with a simple and efficient test setup.
Case study introduction
With more microcomputers used, more and more electrical household appliances can perform more accurately control, which means the appliances can do more complex working procedures. Manufacturers of household appliances now need more advanced measuring devices to test and verify these.
The device under test in this case is an induction multi cooker – capable of roasting, baking, boiling, braising, steaming, frying, and sous-vide cooking - all combined in one appliance with memory function, pre-set timer, and 50 preset programs for various dishes. The cooker even comes with a mobile app adding functions such as a shopping list, preparation videos, and new recipes added regularly.
The customer in this case is a world-famous manufacturer of household appliances in China, BSH Home Appliances Group (BSH Hausgeräte GmbH), founded in 1967 as a joint venture of Robert Bosch GmbH (Stuttgart) and Siemens AG (Munich). BSH has been exclusively owned by the Bosch Group since January 2015. In its over 50 years of history, BSH has grown from a German exporter into one of the world's leading home appliance manufacturers.
Since BSH’s entry into the China market in 1994, and over decades of fast growth, China has become one of the most important global markets for the Group worldwide. Headquartered in Nanjing, BSH China holds five branch companies, operates three production bases in Chuzhou, Wuxi, and Nanjing, and has a research and development center in Nanjing.
The wide range of white appliance products manufactured in China includes refrigerators and freezers, washing machines, laundry dryers, water heaters, cooking appliances, and other home small appliances. In addition, the company imports some appliances like dishwashers and ovens from BSH production bases in Europe.
Household appliance testing issue and application
This is a case of general testing as well as testing quality and safety (electrical safety). The customer wants to verify whether the heating process and complex working procedures of their household appliances, such as an electric kettle or electric cooker, are consistent with the design or not. Multiple signals, such as voltage, current, and temperature need to be measured, but with as few channels as possible.
Previously the customer used traditional multimeters and dynamometers to measure and test, but now they use a Dewesoft SIRIUS - a flexible USB and EtherCAT data acquisition system - and Dewesoft X3 software with a Power analyzer module, an advanced math module for power analysis and power quality analysis.
In addition, through the European headquarters, the customer already knows Dewesoft and uses a custom Dewesoft product, TEST-BOX-HV-10A. BSH in China wished to use the same product and the same specific custom-made system as the company group headquarters.
TEST-BOX-HV-10A allows the measurement of voltage and current, and can at the same time supply the power to the test household appliance. This custom module and flexible DSI adapters can help the customer perform the test and acquire the results needed.
Solution - setup and configuration
The actual testing took place in the customer’s testing laboratory with a Dewesoft SIRIUS data acquisition module, the custom test box module, a thermocouple sensor, and the device under test – the electric multicooker.
Data acquisition system: SIRIUSi-2xHV-2xLV-Ban-2xLV-2xLV+
Current and Voltage adapter box: TEST-BOX-HV-10A
Thermocouple Type K Sensor Adapter: DSI-TH-K
Dewesoft X3 Data Acquisition Software with Power module option
In this case, the SIRIUS data acquisition device with high galvanic channel-to-channel isolation is used. It includes 2 HV (High-voltage) channels, 2 LV (Low-voltage) banana plug channels, 2 LV DSUB9 channels, and 2 LV+ channels with additional digital counter/encoder inputs.
High galvanic channel-to-channel and channel-to-ground isolation explained
In addition, another custom-made product, TEST-BOX-HV-10A, is also used. It’s a test box with a 10A current shunt, which can convert the current signal to a low voltage signal for measurement.
This TEST-BOX is supplied with a measuring cable with banana connectors. For voltage measurements, the supplied cable is connected to the SIRIUS HV amplifier and for current measurements to the SIRIUS LV-BAN amplifier. It includes a main switch for activating the measurement housing, a measuring socket supply to the test household appliance, and a tube fuse 10A.
The Dewesoft DSI® adapters convert any analog input amplifier with DSUB9 connector into a universal analog input that can accept everything from strain gage, IEPE/ICP, LVDT, RTD, current to voltage signals with up to ±200V - and in this case a thermocouple.
The adapters are automatically recognized by the TEDS sensor chip and all settings are configured automatically inside Dewesoft X DAQ software.
To test the multicooker the measuring cable was simply connected to the SIRIUS data acquisition system and TEST-BOX-HV-10A. The socket of the test household electrical appliances was plugged into the measuring socket of the TEST-BOX-HV-10A, as shown in the connection diagram above.
Water was heated by the electric cooker under test – the same procedure would apply for other appliances, e.g. an electric kettle. The voltage and current were measured by the TEST-BOX. The temperature was measured through the thermocouple sensor. The power consumption (energy efficiency) calculation, voltage, and current are calculated and visualized by curves of power and temperature.
TEST-BOX-HV-10A is supplied with power from the overall electric supply, while the device under test - the electric cooker - receives 220V AC from the measuring socket of the custom product TEST-BOX.
The measuring voltage signal from the measuring socket is connected to the banana connectors directly to the SIRIUS data acquisition system, through the HV (high-voltage) amplifier. The current signal is converted into a low voltage signal by the 10A current shunt, and also connected to the banana connectors of the SIRIUS LV-BAN amplifier.
At the same time, the SIRIUS can measure the temperature with the DSI-TH-K thermocouple adapter from the water in the test electric kettle or electric cooker.
Considering that any instability of the electric supply could impact on the final power calculations and the test result, the customer used the power supply from the stabilized voltage supply to minimize the potential sources of test faults of this nature.
More and more modern household electrical appliances use microcomputer boards, and the working procedures of such household products become more and more complex.
For instance, the electric cooker in this case, according to the design of the customer, does not always keep the power of the cooker at its high during all of the heating procedures. In fact, the power will go down when the temperature reaches a certain point and then go up and down again - interchanging until the water in the cooker reaches the boiling point.
It’s a complex process and the manufacturer needs to control it, record the curves of power consumption and temperature, and analyze the results.
Measurement results and analysis
The DewesoftX Power Analysis module was used for the calculation of the power parameters. Almost all household electrical appliances are based on a single-phase power system.
Dewesoft - World Smallest Power Analyzer
To measure and present the measurement results a single-phase power connection just needs to be configured and the power calculated in the DewesoftX software.
Zooming in on the heating part, the blue box part, we can see at the beginning of the heating, the power value is to keep the heating power. But when the water temperature is over about 100 degrees Celsius, the power value of the cooker starts to change down and up, between the heating power and low value.
And then, zooming in on the brown box, indicating the keep-warm function status, the result shows that the cooker is doing some work when this function is active, and the working power transfer is in the range of about 4W to 11W.
Having recorded such a curve of the data, the customer can verify the product according to the design, the power rating, the timing of the work procedures, the work time, and more – finally, gain the knowledge supporting the further improvement of the products.
The testing demonstrated the flexibility and ease of use of the Dewesoft data acquisition systems, the power of the SIRIUS DAQ system with customized front-end, and the custom-made product, TEST-BOX-HV-10A.
In comparison with the data acquisition device previously used by the customer, the Dewesoft SIRIUS DAQ device is much smaller in size, and more flexible, and the included Dewesoft DAQ software is much easier to use. The Dewesoft solution measures all signals in one time-axis, facilitating and thus simplifying the customer analysis of the data.
The customer also benefited from the Dewesoft flexibility and in case more channels are needed in the future, the ease of expansion. Overall connectivity is strengthened as BSH China already has other Dewesoft data acquisition systems in use, and as the headquarters of BSH in Europe is using Dewesoft, test data can now be easily shared and compared.
Even more, the flexibility of Dewesoft software licensing allows customers to read and analyze recorded data files on any computer(s) without any additional software license.
The potential to help facilitate and qualify the development of household appliances is even larger. Dewesoft can measure much more, for example, appliance working noise, the vibration of vacuum cleaners, or the speed of revolution of high-speed blenders - almost everything a customer may need.