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Ice*Meister™ Model 9734-OEM
INDUSTRIAL ICE SENSING ELEMENT

GENERAL DESCRIPTION

Ice*Meister™ Model 9734-OEM sensor element for ice, water and precipitation is a general purpose sensor for all forms of water H₂0. It offers many newfound benefits of ice sensing capability in new applications where ice sensing has never been affordable before, or even available. It senses optically-occluding snow, frost, dew, condensation, and white (rime) ice by their degree of optical opacity. It senses optically-clear water, raindrops and clear ice by their optical index-of-refraction.

Model 9734-OEM monitors both the opacity and refractive index of whatever substance is in contact with the probe surface. There are no moving parts. The sharp point of the probe prevents accumulation of liquid rain and standing water on the sensor; while at the same time it attracts and accumulates ice and other freezing precipitants.

There are four components to the sensor element:

(A) The laser: A semiconductor laser diode that emits up to 200 μW of invisible
950 nm infrared light. Max dissipation = 200 mW, max current = 100 mA.

(B) The optical fiber: A 3mm diameter multimode optical fiber made of polymethyl- methacrylate (also called PMMA, acrylic, or Plexiglas©),integrally coupled to the laser.

(C) The receiver: A semiconductor photodiode detector, whose electrical characteristics match the laser.

(D) The body: A sandwich of two pieces of acrylic plastic, fabricated to hold the laser, optical fiber and receiver in correct orientation to each other. Embedded in your host enclosure, the body blocks out visible light, but passes the laser's infrared light.

At maximum sensitivities, 9734 detects the incipient formation of any kind of ice, and even senses the condensation from human breath. At minimum sensitivities, it distinguishes between heavy ice and slightly heavier ice in a refrigeration system.

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FEATURES

DC operation
No MHz clock
Lightweight
Low cost parts
Low cost labor
Nothing to break
Low cost fabrication
3mm diameter probe
Extends 3/8 inch from face
No loose parts
One-piece solid acrylic construction
Sensitive to the first 0.001" of ice, or better.
Acrylic structure embeds easily into host enclosure
Four elements fused together: laser - fiber - body - receiver

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BENEFITS

Prevents irrigation and lawn sprinkling during rainfall; prevents sprinkling over ice.

Simple
Robust
Lightweight
Low cost
Adaptable
More sensitive than hydroscopic discs
No moving parts
Real time operation
Instant sprinkler shutoff
Instant reset after rain stops

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APPLICATIONS

Ice*Meister™ optical sensors are predictable, adaptable, low cost, robust and effective. They sense all forms of opaque and clear ice and precipitation in any ground-based application, including motor vehicles. They are for use in a variety of applications ...

Agricultural, commercial and residential sprinkler controls,

Vehicle dispatch offices
Windpower farms
Industrial freezers
Tethered blimps
Radio broadcast towers
Suspension bridges
Roadway ice warnings signs
Meteorological stations
Vehicle windshield wiper controls
Weather stations
Wireless networking
Grocery stores, supermarkets
Household refrigerator defrost controls
Oil & Gas installations
Ice-indicating municipal traffic signals
Household indoor-outdoor weather stations
Heliports and helipads at hospitals, police stations, offshore oil rigs, etc.
Water level sensing

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INTERFACE BOARD

User interface board is radio silent, has no MHz clock. Board weighs 1 oz, measures 1.5" x 4.75", operates to -40 ℃, can be enclosed in a NEMA 4X box.

Model 9733 Universal User Interface Board with description of circuits.

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PRINCIPLE OF OPERATION

Ice*Meister™ sensors are optical in nature. The 3mm diameter probe monitors the optical characteristics of whatever substance is in contact with the probe surface (air, water, or any kind of ice or precipitation). It reliably and instantly differentiates between air molecules and H₂0 molecules, either solid or liquid phase. No accumulation of water is required to detect rain. Individual raindrops are sensed in real time, as they impinge on the sensor.

Model 9734 works on the twin principles of optical occlusion and optical refraction.

An infra red laser generates an excitation signal of invisible light. The light is coupled to an optical fiber. The fiber is oriented to a receiver through an infrared filter.

Optically-occluding precipitation such as dew, snow, frost, condensation and white (rime) ice become interposed between the fiber and the receiver, which analogously attenuates the signal in response. The refractive properties of clear ice, water, and raindrops act upon the probe in such a way as to simulate occlusion in a step-function, switching between the refractive indices of air and water. Model 9734 simultaneously monitors for both occluding and refractive precipitants.

Either by occlusion or refraction, all H₂0 precipitants attenuate the excitation signal on its way to the receiver; air causes no attenuation. A user interface board senses this difference and reports it to a user's host system.

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WIRELESS NETWORKING

Model 9734 sensor element can be separated from its interface board by as much as 200 feet. New Avionics Model 9733 universal interface board is available, and customers are welcome to design and fabricate their own application-specific housings and interface boards under a simple, low cost licensing arrangement. Interface boards may incorporate or link to any of numerous wireless-networking solutions readily available.

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CONNECTION PINOUTS

pin 1:
receiver anode
long lead
white color code
round thru-hole pad

pin 2:
receiver cathode
short lead
green color code
square thru-hole pad

pin 3:
laser anode
long lead
round thru-hole pad

pin 4: laser cathode short lead, red color code square thru-hole pad

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SPECIFICATIONS

height	2.00" +0.05" - 0.00"
width	0.75" + 0.05" - 0.00"
thickness	0.24" + 0.03
probe extension forwards	0.50"+ 0.10"
power consumption	200 mW max
storage temp	- 65 deg C to + 70 deg C
operating temp	- 40 deg C to + 70 deg C
sensitivity	0.001" of ice or better
weight	10 grams max

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REAL-TIME RAIN SENSING SPRINKLER CONTROL

Model 9734-OEM sensor element is useful as part of an optical rain detector for sprinklers and general irrigation control. With it agricultural, commercial and residential sprinkler controls can prevent costly overwatering during natural rainfall by shutting off the sprinkler's main valve, and restoring normal operation as soon as the rain stops.

Ordinary sprinkler controls rely on a spongy material to expand when it gets wet, but this delays shutoff of the water valve for a substantial amount of time after it begins to rain; Thus, system sprinkler heads can often be seen spraying valuable water during periods of natural rain.

The 9733 interface board's reaction to each individual raindrop falling on the sensor element face is to trigger a monostable multivibrator (1-shot), beginning with the very first raindrop to hit the face. This produces a 10-second output pulse which activates the RAIN relay and display LED for 10 seconds.

If subsequent raindrops continue to fall on the sensor face, the 10-second timeout is continually reset, and so the RAIN signal remains asserted TRUE for the entire duration of natural rainfall.

When the last raindrop falls and no others follow it, the 10-second timer times out and allows the water control valve to operate normally again.

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WATER SAVER

Because there is no required accumulation of rainwater after the onset of rain, this feature completely eliminates all time delay before the sprinklers shut off. Because there is no drying out period required after the rain stops, 9734 completely eliminates any time delay before the sprinkler system returns to normal again.

Used in conjunction with ICE ALERT, the RAIN signal can prevent sprinkling water on already-frozen surfaces.

Model 9734-OEM digital go/no-go sensor elements offer precise control for...