Case Studies
Power Glitch Monitoring on Treadmills
A customer develops gym equipment such as treadmills. The requirement is for an inexpensive way to monitor voltage signals for long periods of time. The treadmills are controlled by microprocessors that drive the LED displays. The customer has observed that some units intermittently fail during testing, a condition known as a "glitch" or a "brown-out". A glitch can have many causes, one of which is a weak power supply. The customer needs to capture certain key signals when a glitch occurs. At that stage, based on the captured data, it can be determined if the power supply is weak and should be changed before delivery of the unit.
The microprocessor runs at 12 MHz, therefore minimum sampling rate to meet the Nyquist criteria is 25 MS/s. One channel is sufficient as there is only one power line. A glitch in the power supply will be easily detected with 8 bit vertical resolution. Monitoring for glitches must be done for long periods, such as tens of minutes. Free application software is desired due to budget constraints.
GAGE'S SOLUTION
CompuScope 225 is an 8 bit, 50 MS/s A/D and scope card for the ISA Bus. The minimum on-board memory of 128 K is affordable and will meet technical requirements. Should the customer ever develop his hardware to test 2 power lines (i.e. 2 treadmills) at once, the CS225 is able to meet the Nyquist criteria in dual channel mode at 25 MS/s per channel. 50 MS/s in single channel mode is optimum as the current solution.
The glitch may occur at any time, thus the need for long monitoring periods. In order to accomplish this with the CS225, the customer will be able to set a trigger level that satisfies the conditions of the glitch. One MegaSample of on-board memory will allow 40 millisecond captures at 25 MS/s, which exceeds the maximum expected glitch duration. Should no glitch occur, the acquisition card will not trigger (but will remain armed) and thus not use any of the valuable on-board memory. The customer is fortunate in the sense that the low-cost CS225 will be discontinued at the end of September 2001. Otherwise, the alternative would be a higher performance CompuScope 1450 14 bit, 50 MS/s A/D and scope card for the PCI Bus. Complete support for the CS225 will remain for the foreseeable future.
GageScope for DOS (6.22) free application software will enable the customer to capture and save data, as well as set trigger conditions without writing a single line of code.
PRODUCT RECOMMENDED
CompuScope 225 - 1M
GageScope for DOS (free application software)
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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