Ways to to use motor controllers and encoder interface cards for scanning
Both Winspect and InspectionWare can be configured in many different ways to collect NDT data. This document describes what you can do with Winspect or InspectionWare given certain hardware configurations.
Data and images can be collected and stored even without position information, so you can do quite a lot of useful work with minimal hardware.
1) acquire ultrasonic signals and data (with no motion hardware)
With only a pulser receiver and a digitizer, it is possible to view and store A-scans (just like with a flaw detector). Analog data from any flaw detector, instrument or sensor output can also be recorded using a low-cost data acquisition card. Both Winspect and InspectionWare directly support a wide variety of ultrasonic instruments and digitizers.
It is possible to produce strip charts and B-scans using either a "timer based scan" or a "one-axis scan" where the PC mouse is used as a position sensing device. With a mouse that tracks well, it is even possible to produce coarse C-scans.
Point-by-point scans are used to collect data in a grid, by manually positioning the probe and recording a data point. Points collected on a X-Y grid produce useful C-Scan images. This type of scan is often used for mapping variations in material thickness.
2) perform manual scanning (reading scanner position information)
This is accomplished with an encoder interface card installed on the PC bus, or with an instrument that has an encoder input. It can also be accomplished with the encoder interface portion of a motor controller card. With an encoder interface card, Winspect and InspectionWare produce C-scans by following the position of a manually controlled scanner.
3) perform externally controlled or "along for the ride" scanning (reading scanner position information)
Both software platforms can also operate in an "along for the ride" mode where a motorized scanner's position is followed. This enables a low cost upgrade to older scanning systems. The scanner's existing motion control system perform the scan as usual, while the software monitors the axis positions passively. Encoders are not necessarily needed if the scanner uses stepper motors. Both Winspect and InspectionWare can monitor the motor step and direction signals.
4) perform automated scanning (software controls scanner positions)
This is accomplished with a motor controller card such as a Compumotor or one of Galil DMC series (for servo or step motors).
With a motor controller card, Winspect and InspectionWare can directly control all of the axes of a scanner, to produce B-scans and C-scans. It is also possible to record the RF waveform at every pixel thereby inspecting the entire volume of the material under inspection. Multiple axes can be controlled together for more complex motion, such as scanning along slopes and curved paths.
5) perform higher-speed scanning (encoder information read by a fast interface card)
Some systems have both a motor controller card and an encoder interface card. Even though the motor controller can report encoder positions to the NDT software, some controllers can only do so at limited rates. This limits the inspection speed to around the 500 Hz range. For many applications, this is fast enough, so an additional encoder interface card is not always needed.
If scanning speeds in the 500 Hz and above range are needed, an encoder interface card is required so that the software can receive position information at a faster rate. In such a configuration, the encoder signals are wired in parallel to both the motor controller and the encoder interface card. The pulse repetition frequency (PRF) for this configuration will be in the 1-8 kHz range.
6) perform highest-speed scanning (encoder information read directly by the UT instrument or digitizer)
To achieve the fastest possible scan speeds, the ultrasonic instrument or digitizer must read the position information directly from the encoder, without involving the host PC. Two modes of operation are generally used: position stamped and pulse-on-position.
Position Stamped: The digitizer reports the data along with the position at which the data was collected. This mode is often used where the pulse repetition rate or scanning speed changes during the scan, such as when using a turntable for scanning discs.
Pulse-on-Position: The digitizer triggers a pulse on regular intervals, based upon the number of encoder counts.
InspectionWare supports several ultrasonic instruments and digitizers that are capable of these advanced operating modes.
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