 |
When do you need an
Air Bearing LVDT Contact Measurement Probe?
|
|
 When You Want to Increase the Quality
Assurance of Your Metrology Department
When quality assurance is your goal,
measurement of a part feature must be performed by a measurement
device that is capable of exceeding the part tolerance. Generally,
in order to obtain statistical confidence in one's measurement,
the measurement capability must exceed the feature tolerance
by a factor of ten. For example, one cannot measure a .0001 inch
feature with a .000050 inch resolution indicator with high statistical
confidence. The high resolution capability of the Colorado Precision
Air Bearing LVDT enables measurements with high statistical confidence.
The probe is capable of high confidence measurements in the +/-
.020 inch range and also demonstrates repeatable high confidence
measurements at the atomic level (see examples). |
|
When You Need High Resolution Over
a +/- .020" Range
In certain applications, measurement
to high resolution over large indicator ranges is required. With
the appropriate amplifier,as recommended by Colorado Precision,
1-microinch resolution is available over a +/-.020" range.
When measurements taken are being performed over a +/-.020"
range, the effect of varying stylus force becomes a critical
concern, especially if microinch level accuracy is required.
With a Colorado Precision Air Bearing LVDT, constant stylus forces
over the total range of travel provides accurate high resolution
measurements over relatively large ranges. Varying stylus force
is not a concern. |
|
When You Need to Make Very Accurate
Contact Measurements With Very Light Stylus Forces in Order to
Avoid Damaging Fragile Surfaces
In certain applications, it is difficult
to use spring-based mechanical indicators where fragile surfaces
are being measured and care must be taken to not scratch, chip,
dent or move the surface being measured. Often, for example,
soft metals or plastics cannot be scratched, diamond edges or
sharp edges cannot be chipped, and measurements of thin threads
or wires cannot initiate deflections. The Colorado Precision
Air Bearing LVDT has stylus force adjustable down to 1/10 of
a gram and can be very realistically used at 2/10 of a gram stylus
force. At Colorado Precision, we often use light stylus contact
forces in the measurement of diamond turned glass and metal surfaces
where we cannot use spring-based mechanical indicators. |
|
When You Want to Avoid Direction
Reversal Errors and Radial Loading Errors Associated With Spring-based
Measurement Devices
Measurements using spring-based electronic
indicators are difficult when the direction of contact measurement
is reversed. When the load direction is changed on a spring-based
measurement device, often the measurement being taken jumps significantly
and must be ignored as direction reversal error in the indicator.
With the very light stylus forces available with an air bearing
LVDT, and constant stiffness in different radial directions,
reversal errors associated with measurement direction reversal
have been extremely reduced. Direction reversal error with an
air bearing LVDT is generally less than 0.1 microinch, negligible
in most measurement applications. |
|
When You Want Extremely High Resolution
Contact Measurements Over Small Ranges, Such As .05 Microinch
Resolution Over +/- 20 Microinch Range
In certain applications it is difficult
to make accurate contact measurements with spring-based mechanical
indicators below 20 microinches. The stylus force in the Colorado
Precision Air Bearing LVDT is controlled by differential air
pressure between the front and back of the stylus shaft. In an
air bearing LVDT, there are no spring mechanisms. As stylus force
is not dependant on springs, the stylus force is constant over
the total range of travel (.200 inches). Accurate measurements
below 20 microinches are difficult to make using spring-based
indicators which have varying stylus forces over the measurement
range and low radial stiffness.
The Colorado Precision Air Bearing LVDT has demonstrated its
effectiveness and repeatability when making contact measurements
of .05 microinch resolution over a +/-20 microinch range (see
performance specification sheet). There are few, if any, contact
indicator type probes, with the versatility and ease of use of
the air bearing LVDT, that can compete with this level of accuracy
and still operate in ranges as large as +/-.020 inches. |
When you need the
very best in contact measurement instrumentation
|
