Author(s):
Pasit Seangvilai

Company:
Sony Technology (Thailand) Co., Ltd

Product(s):
NI LabVIEW 8.2
NI Sound & Vibration Measurement Suite 5.0
NI LabVIEW Report Generation Toolkit 1.1.1
NI PXI/CompactPCI (NI PXI-8186 P4 2.2GHz Controller, NI PXI-1044)
Data Acquisition (NI PXI-4461, NI PXI-4462, NI PXI-6515),
Modular Instruments (NI PXI-4071)

The Challenge:
To develop real-time automated measurement systems for the newest product—the 8.1ch DSP power amplifier. This product will be installed in the automobile, it features up to nine surrounded speakers, therefore, the test process is very complicated and requires the measurement systems that should be fast, correct and accurate, to meet the total productivity rate. The test systems must be low-cost, compact and rugged, in order to support 24/7 operations.

The Solution:
Sony chooses PXI modular instruments for high stability and small footprint; all instruments are integrated into one compact chassis so the system can be relocated easily. We use the PXI-4461, DSA to generate the sine balanced signal pair from 20 Hz to 20 kHz and pass to amplifier’s inputs, which requires 4461’s two output channels. On the other side, we connect amplifier’s nine balanced output channels (equal to eighteen unbalanced channels) to five modules of PXI-4462.
The safety is also one of the serious considerations, because the test process consumes high supply current, up to 40 A DC, so it is important to monitor the voltage and current in the system. In this case, we use the PXI-4071 DMM to measure, and the PXI-6515 digital I/O to control the relays that connect the power supply to the components, it also acquires the digital signal from sensors. All modules are integrated into the PXI-1044, 14-slot PXI chassis, this makes system compact and easy to move and setup, also we save a lot of cable and accessory.

Current System Introduction:

The “8.1ch DSP Power Amplifier” is the latest product from Sony, the target launch date in American car market will be in middle 2008. Most of the parts in this product are redesigned from analog to digital system, the audio processing tasks such as noise filtering are performed by digital signal processing (DSP) chip, the communication part is based on the standard CAN bus. This special amplifier can connect with up to nine speakers or the so-called 8.1-channel, which delivers the power at 35 W per channel.

This product had been designed by Japanese designer since early 2006, and finished in early 2007. After that, a test system was set and did a trial run. With this test system, we experienced many problems, since the number of channels is high, the electrical characteristic tests e.g. frequency response, SNR, % Distortion, CMRR, also consumed very long time, finally it took 30-35 minutes per one amplifier. Due to the instrument (Panasonic), it can test only one channel at a time so we had to switch the circuit using relays to test all nine channels, with long test time, the amplifier accumulated the heat, finally the high temperature made the measurement highly inaccurate. Another problem was, if one amplifier took 30 minutes to test, we had to prepare 90 systems plus factory space to handle the productivity at 600 units per day, which would be more than THB 43 million of investment.

New System Introduction:
From major problems that we faced, we tried to find a solution to test all 128 important requirements; finally we decided to replace the old system with Nation Instruments products. Due to that time, we had no confidence about NI PXI instruments, but we had good experience in some of NI products such as digital I/O card, USB-GPIB, etc so we made the decision from this point.

We chose the PXI for ruggedness, high efficiency, high stability and small size, all instruments plus a controller are integrated into one compact chassis, which saves a lot of space. We also replaced the MS Visual C#.NET with the NI LabVIEW 8.2.



The result is we can reduce the test period from 30 minutes to only 3 minutes. Hence the test systems that we have to prepare will be only 9 systems, which reduces the investment almost 3 times