This NOV CTES Depth Measuring System, or DMS, helps to improve the accuracy
of CT depth measurement. An ordinary depth counter's accuracy is hindered by depth wheel slippage. The DMS design works to help alleviate this problem in three ways: - To reduce slippage, the DMS uses a lever-arm movement to maintain a high frictional contact force between the measuring wheels and the tubing.
- Also to reduce slippage, the DMS uses two tungsten-coated stainless steel measuring wheels to help increase accuracy and dependability in harsh operating environments.
- To correct for slippage, the DMS incorporates a microprocessor to run the "Fastest Wheel Algorithm," or FWA, while continually monitoring the speed of both wheels' electronic position encoders. The bottom wheel serves a master depth and the top wheel serves as backup depth. The top wheel takes over as master when the bottom wheel's speed is slower from slippage. The DMS displays a "composite" depth value.
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