One point of differentiation between optical and galvanic DO sensors is that galvanic DO sensors exhibit flow dependence. Optical DO sensors require no minimum inflow velocity.
Some sample constituents may interfere with measurement accuracy. Hydrogen sulfide, for example, a compound found in wastewater, lake bottoms, and wetlands, can permeate the galvanic sensor membrane. An optical dissolved oxygen sensor would make a better choice in these environments, as these sensors are not susceptible to interference by H 2 S.
Galvanic DO sensors respond x faster than optical DO sensors depending on the membrane material. This limitation of optical DO sensors is more cumbersome in applications where a high number of sample measurements will be taken. Response time is typically not a limiting factor when choosing a DO sensor for continuous monitoring applications.
The table below summarizes advantages and disadvantages of the 3 primary methods for measuring dissolved oxygen concentration in water:. Previous Next. It can be rotated manually or automatically, and can accommodate many different stylus tips and attachments. These features make the trigger probe a versatile and flexible data-gathering device. Touch trigger probes eliminate the influence of operator touch on measuring results and can be fitted on direct computer control and manual CMMs.
An improvement on the basic touch trigger probe design incorporates piezo-based sensors. These sensors translate the deflection of the probe into a constant digital acoustic signal that is recorded by the CMM.
This design improves the accuracy of touch trigger probe measurement results because it eliminates the effect of stylus bending caused by force variations when the touch trigger probe contacts the work piece and inaccuracies caused by the probe's internal electromechanical parts.
A further improvement is the use of strain gage technology. This principle of operation effectively triggers the probe at a constant force no matter what the probe's contact angle with the work piece. The design eliminates direction sensitivity common to other touch trigger probes. Submicron accuracy is possible, even with long stylus combinations. Analog scanning probes are a type of contact probe used to measure contoured surfaces such as sheet metal assemblies.
The analog scanning probe remains in contact with the work piece surface as it moves and produces analog readings rather than digital measurements. Continuous analog scanning is a relatively new technology. It adds versatility to CMMs by offering dramatically increased levels of data acquisition, which speeds and improves the accuracy of measurement and inspection operations.
CAS technology is based on continuous rather than point-to-point acquisition of data with specialized probes and software. It is particularly useful for gaging and surface-mapping complex, contoured shapes, including crankshafts and cams, turbine engine blades and prosthetic devices.
It is also suitable for inspecting the form of large sheet metal assemblies, such as automobile bodies. Continuous analog scanning systems can acquire 10 to 50 times more data than traditional touch trigger probes in a given amount of time. The added data provides users with more confidence in the measuring and inspection process.
More confidence may be needed if there are large gaps between data points using point-to-point probing techniques. CAS allows users to scan irregular shapes. This is particularly valuable for measuring work piece features that change continuously, such as the arc on a turbine blade. The ability to acquire data in this manner also allows CAS systems to be used in reverse engineering applications where a new part has to be built to match or fit an existing part.
Form and shape measurement require a different approach than prismatic parts measurement. CMMs used in form measurement applications must be capable of collecting large amounts of data quickly, and measurement software must be capable of processing this data accurately. What does each type of space probe do? What are some examples of each type of space probe? What are two examples of data that space probes gather?
How do scientists access the gathered data? Transmission antennae on the space probes send this data to Earth. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Media If a media asset is downloadable, a download button appears in the corner of the media viewer.
Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. Solar System. View Collection. Hubble Space Telescope. View Photograph. The History of Space Exploration. View leveled Article. After the probe entered Saturn orbit, the moons of the giant planet became important gravitational bodies. Their locations have been determined to an accuracy of a few kilometers relative to Saturn.
The final component of accurate navigation takes all of these other elements and, using models of the forces acting on a probe and orbital dynamics, estimates its location. By taking regular measurements over a period of time, a probe's position and velocity can be determined.
For example, Cassini's location is typically determined to a kilometer or less relative to Saturn. Using a probe's known position and velocity, its future positions can be worked out.
Navigators compare these positions to the predicted location of the target body--based on the ephemeris--to determine when a probe will reach its target.
Then, all that's left to do is to collect the flyby data, take a deep breath, and go on to the next encounter. Sign up for our email newsletter. Already a subscriber? Sign in.
0コメント