Oil-well pump instrumentation device and surface card generation method

The polished-rod dynamometer of claim wherein the firmware for identifying a reference tick of each polished-rod stroke is performed by processing the readings from the accelerometer by:

• estimating a bias by averaging the readings from the accelerometer over a time period longer than the duration of a said each polished-rod stroke;
• subtracting the estimated bias from the readings from the accelerometer and integrating to determine estimated polished-rod velocity;
• and
• searching for maxima or minima in the estimated polished-rod velocity to determine the reference tick.

A method of monitoring a polished rod of a pumpjack, comprising:

• providing at least one axial load sensor configured to monitor axial load on a polished rod, the axial load sensor being selected from a strain gauge and a load cell;
• reading an accelerometer configured to measure axial acceleration of the polished rod;
• identifying a reference tick of each polished-rod stroke to determine a duration of said each polished-rod stroke;
• estimating position over each polished-rod stroke from readings from the accelerometer by:
• computing and subtracting a mean acceleration from the readings from the accelerometer over the duration of said each polished-rod stroke to determine gravity-corrected accelerometer readings,
• integrating the gravity-corrected accelerometer readings to estimate velocity;
• computing and subtracting a mean velocity from the estimated velocity over the duration of said each polished-rod stroke to generate a corrected velocity;
• integrating the corrected velocity to estimate polished-rod position throughout a polished-rod stroke, and
• scaling the estimated polished-rod position so that a range of estimated polished-rod position matches a known position range of the polished rod.

A wireless inclinometer in a first housing adapted for mounting on a walking beam of a pumpjack at a known location relative to a saddle bearing of the pumpjack, the inclinometer comprising:

• sensors selected from the group consisting of first and second physically separated accelerometers and a collocated first accelerometer and rate-gyroscopic sensor;
• a processor having associated memory with firmware residing in the memory, the firmware being configured to read the sensors and compute therefrom an angle of the walking beam corrected for acceleration;
• a first real-time clock;
• and
• a wireless communicator configured to transmit the angle of the walking beam with an angle-capture time from the first real-time clock to a polished-rod dynamometer.