Stepper motors

The external trigger input allows automatic inspections and ultrasonic imaging. The clock signal of an encoder or of stepper motors can be used as a trigger for the pulser. An internal software controlled divider allows different scan resolutions. 

The HILL-SCAN 30XX boards can be used in different PCs. Desktop- and tower-PCs as well suited for laboratory uses. For in-field inspections rugged notebooks and portable PCs are advantageous. A typical portable system is shown in Fig. 2 (USPC 3010), used in MUSE (Mobile Ultrasonic Equipment). This portable PC not only contains the boards for ultrasonic testing but also a controller with power supply for stepper motors, so that a manipulator can be connected directly. The MUSE system is enlarged with a water circulation system which enables a local immersion technique" for in-field inspections. A typical result is shown in Fig. 3, which presents a D-scan of a CFRP- component in RTM-techniques. The defect area caused by an impact is clearly indicated. The manipulator is described in [3]. 

Disadvantages. Again, a specialized probe-head is necessary to allow the rotor axis to be changed, usually usmg a stepper motor and a pulley system. Angle switching needs to be as fast as possible and reproducible. 

To quiet a noise-generating mechanism, the first impulse is often to enclose it. Sometimes an enclosure is in fact the best solution, but not always. If it can be determined what is causing the noise, appropriate action can be taken to be more specific and provide a cost-effective fix. In some cases the problem is caused by a component such as a stepper motor or gear set that does not produce objectionable noise by itself. The trouble typically develops because a small noise is transmitted to a metal frame or cabinet that then serves to amplify the sound using a plastic cabinet can isolate the noise problem. 

Although no attention has been given to the actual stirring process, various drive systems have been evaluated from the simple mains electric (17) and pneumatic units (18) available commercially, through stepper motors to the small modern DC units. Although extremely accurate the former were found to be somewhat short of power, rather prone to stall and then, very difficult to re-start. 

In the schematic the detector coil (hatched boxes) and its associated field lines are shown (dotted) and are seen to be always orthogonal to the permanent magnet field lines (solid). The magnitude of the static field is constant in the horizontal plane (thick black line). A stepper motor and gear-drives for raising the whole assembly relative to the external surface are visible in the photograph. 

Mobile phase is displaced from a chamber by using a variable speed stepper motor to turn a screw which drives a piston. The chamber has a volume of 200-500 cm3. The flow is pulseless, and can be varied by changing the motor speed. The mobile phase capacity is limited to the volume of the solvent chamber. Although this is fairly large, so that many chromatograms can be run before the chamber has to be refilled, a lot of solvent is wasted in flushing out the pump when a change is required. 

In subprograms for operating scanning devices, the primary algorithm may include a do and wait operation (for a stepper motor) or a do and look operation (for a servo system). Try to avoid problems that could arise if you move your software to a faster, newer PC. With a new PC running at a faster clock speed than an old one, the faster do operation will require a longer wait if the scanner operation is matched to the duration of do + wait. Thus, the CAM should be treated as three separate units the microscope, the interface, and the PC. The PC will become obsolete before the microscope. 

Many laboratories are equipped with commercial video frame grabbers and video image analysis systems, the operation of which is nicely explained by Russ (5). Many of the concepts involved apply both to video analysis and to the analysis of matrices obtained with a mechanical scanning stage driven by a stepper motor. Video scanning is very rapid, but slow mechanical scanning can be very precise and accurate. 

Programming instructions for scanning-stage stepper motors (or monochromator stepper motor, etc.) may contain a bit pattern that reflects the structure of the motor. For example, to step in one direction the POKE instructions to the motor address may be 3,6,12, and 9, which may look illogical until you consider the respective bit patterns, 0011,0110,1100, and 1001. Sending in reverse order will step the motor in the opposite direction. 

Not only must space MS be compact, low power, and autonomously operated, but they must survive launch by rocket. The trend over the past few decades has been toward solid-fueled rockets or boosters that have a much rougher ride than liquid-fueled rockets. Over-zealous specifications often require that space MS survive 15 g of random shake acceleration, which is about like lifting the instrument 10 cm and dropping it on the floor repeatedly. All those shims in a magnetic sector MS must be capable of being realigned in space, perhaps with stepper motors, which is what ESA had to fly in its 2011 comet mission [19]. Likewise, carbon foil technology took an additional 10 years to fly after it had been developed in the laboratory, primarily to ensure that it survived launch. 

Figure 4 shows peak area precision vs. injection volume for a typical autosampler. Note that excellent peak area precision of 0.2% RSD was readily achievable for an injection volume >5 J,L. Precision levels are much poorer (0.5-1% RSD) for sampling volumes <5 J,L, attributable to the finite resolution of the sampling syringe and associated digital stepper motor. To obtain optimum peak area precision, the analyst must avoid potential problem situations such as an overly fast sample... 

FIGURE 4 Peak area precision study to evaluate the effect of injection volumes. The resolution of the sampling syringe was about 0.01 jlL as determined by the digital resolution of the stepper motor and the size of the sampling syringe. 

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