Case Studies
Improving the Performance of Gas Compressors
A customer who is a manufacturer of natural gas compressors is seeking to improve the efficiency of their 12-cylinder diesel engines. These diesel engines are used to drive the gas compressors.
The performance of the engines is analyzed from the position of the engines' shaft, which is detected by an optical encoder. The output from the encoder is a 12 kHz jittery clock with variable pulse width. The jitter has high frequency components and the jitter variation can go down to 0.1 microsecond and varies systematically with wear, load, fuel and other engine conditions. The customer captures different encoder cycles, and now wishes to simulate these cycles electronically in order to predict engine conditions, the need for maintenance, preventative maintenance and to generally optimize the operation of the engines.
GAGE'S SOLUTION
The bandwidth of the jitter is calculated as the inverse of 0.1 m s, which equals 10 MHz. This output bandwidth requirement is met by the Gage CompuGen 1100 Arbitrary Waveform Generator card. In order to reproduce the optical encoder pulses, the customer needs to configure the CG1100 to be as close as possible to the original waveform. The conversion rate must be at least 10 MS/s in order to properly reproduce the jitter.
The customer required continuous looping of the waveform in order to simulate the continuous turning of the diesel engine.
Using the base memory of 512 kiloSamples, generating at 10 MS/s will allow the customer to generate a distinct signal with a duration of 512 kS / (10 MS/s) » 50 milliseconds. After this 50 ms, the pattern will seamlessly loop back to the beginning and repeat itself indefinitely.
The 12 KHz clock has a 1/12 KHz » 83 m s period. Consequently, the 50 ms pattern will consist of 50 ms / 83 m s = 600 distinct cycles, which was judged sufficient for the application.
Initially, the customer will generate signals with CompuGen for Windows arbitrary waveform generator software under Windows by creating several prepared pattern files. For greater flexibility and programmatic control, a more sophisticated custom application will be developed in LabVIEW using the CompuGen Software Development Kit for LabVIEW.
The Gage CG1100 enables this customer to reproduce various engine conditions with a high degree of accuracy.
PRODUCT RECOMMENDED
CG1100 - 512K
CompuGen for Windows (CGWIN) Arbitrary Waveform Generator Software (included)
CompuGen Software Development Kit for LabVIEW
This application note is provided "as is" without any warranties of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. Gage Applied Technologies further does not warrant the accuracy and completeness of the material contained herein. Gage Applied Technologies may make changes to this material, or to the products described in it, at any time without notice.
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