The QVLA® process is the LED-based technology which is used by Motion Controls inSight® sensor. The QVLA® process works by utilizing an ultra-stable LED light source to fill a volume with diffuse light. The filled volume, called the “sensing volume” can be almost any enclosed volume. Since Motion Controls is a pneumatic cylinder company, the first use of the inSight® sensor utilized the inside of an air cylinder as the sensing volume. As the sensing volume changes, the amount of light measured in the sensing volume varies and can be resolved into linear or, given the correct shaped sensing volume, rotary motion. This process is performed by our inSight® sensor which is rugged, inexpensive, fast, and non-contact. Thus far, inSight® has been used to sense the position of industrial machinery, replacing traditional potentiometers, LVDT’s, and magnetostrictive sensors all at a reduced cost and higher mean time between failure (MTBF). Our inSight® Series of cylinders is now available with inSight® sensors completely integrated into any size of our D Series air cylinders. InSight® Series cylinders are able to provide position feedback in the same footprint as a normal D Series actuator. The inSight® sensor can also be purchased as a stand alone sensor for custom applications or even licensed for seamless integration into your own product line.
Flood two different sized volumes with light sources of equal intensity.
Measure the light intensity within each volume.
The disparity between light intensities inside the volumes reveals the difference in volumes (X-Y).
Experimentation proves light intensities accurately measure volume.
Bellows expansion and/or retraction, fluctuating fluid levels and mechanical movement of walls are all examples of volume changes measurable by QVLA®.
The light emitter must be uniform in its output unaffected by time, temperature or changing ambient light levels. The light emitter is synonymous with a ruler. Presently, the patented QVLA® light emitter has a frequency response > 15,000 Hz. Lifetime is calculated at greater than 100 years.
Reading the ruler is cost critical. Applying only what is needed for an application is important; analog solutions are least expensive, digital solutions with communications protocols can cost more
For discussion, imagine having a QVLA® emitter inside an air cylinder. For every movement of the rod there is a corresponding change in light intensity inside the volume as depicted to the right. Light intensity is lowest at maximum rod extension/greatest volume as shown with the top volume to the right. The bottom volume represents less rod extension and brighter internal volume.
In the top configuration the rate of light intensity change per correlating stroke or volume change is the smallest. This is the point to establish resolution.
Using a reference voltage of 4.096 volts with 16 bits of resolution yields increments of .0000625 volts (4.096 ÷ 65,536 = .0000625).
A 2½ in. bore air cylinder with a 10 inch stroke has a light intensity variance of .0172 volts at the last inch of stroke. Dividing .0172 by our resolution of .0000625 we get 275.2. Divide 1 by 275.2 we get a theoretical resolution of .0036 inch for the last inch of travel. Considerably higher resolutions are possible with shorter stroke cylinder/smaller volume or closer to the light source.
Experimentation with light intensity, reference voltage, resolution bit choice and analog circuitry will yield substantial results for surprisingly good value.
QVLA® is a precise, repeatable and long lasting measurement system working on the simple principle of measuring light intensity within the air cylinder. As the piston moves more cylinder wall is available to absorb light thereby resulting in changing light intensities within the cylinder indicating rod extension.
iNSiGHT® replaces reed switches providing identical electronic outputs, easier set-up by a permanently attached keypad on the outside of the cylinder and can also be used for an end of stroke sensor. Unlike traditional switches, which can be run over with speed, iNSiGHT® establishes “end zones.” Once a position is tripped an “end zone” of switched electrical signal is established.
iNSiGHT® has no magnets or coils, extremely low electrical noise and is inherently wield field immune. It works with steel, aluminum or opaque composite structures.
iNSiGHT® Series cylinder is made in two footprints. The “Dprint” is our basic D Series cylinder line with 1.25″, 1.75″, 2″ and 2.5″ bore cylinders. The “Kprint” is our NFPA K Series cylinder with 1.5″, 2″, and 2.5″ bore cylinders. All typical mountings available.
9 foot cable standard.