Technical Information

The Proxwitch is a 5-wire material detector and switch. It uses a changeover relay and not a transistor or thyristor which gives the Proxwitch several key advantages:

Switching contacts are isolated from the supply voltage

Output circuitry is more electrically robust and less susceptible to external damage by the user

Can switch loads on or off

All models, regardless of supply voltage can switch up to a maximum of 5A (resistive), 240V AC

Where is necessary to switch greater loads, the Proxwitch may be used to drive the coil of a contactor with sufficient rating to operate the larger device.

Power Supply Options

The Proxwitch has an inbuilt power supply. It is available in 220-240V AC, 110-120V AC, 24V AC/DC and 12V DC models. The 12V DC model is for in-dash vehicle applications, such as combine tanks, seed drills, sprayers or indeed wherever vehicles receive and dispense liquid or granular materials

Specifications

Case	ABS, filled
Dimensions	31mm diameter x 134mm long
	1.5m cable length
Detection Range	<= 25 mm (material dependant)
Temperature	-10C to 55C

The Proxwitch range has been fully approved to be CE marked for safety conformity after stringent checks to British Standards by an independent, Government-approved test house.

TECHNICAL ASPECTS OF PROXIMITY SWITCHES

There are two basic types of proximity detector, inductive and capacitive.

Inductive types only recognise the presence of ferrous materials - iron and steel and are used in large quantities in automatic metalwork production. They are plentiful and cheap due to their simplicity.

Capacitive Switches, such as the MJP Proxwitch range, are much more complex and adaptable. They can not only detect ferrous items but most other metals too, as well as granular materials such as grain, animal feedstuffs, plastic pellets, bulk powders including flour, cement, aggregates and even liquids,water,oil etc. When the material approaches the front face of the Proxwitch, the appropriate control machinery is automatically switched on or off as required.

Proxwitches are the modern, rugged and reliable answer to problems with old fashioned "paddle switches" traditionally used for the task. These have a plate sticking out into the material flow that rises with the level and operates a micro-switch. Both paddle and switch are notoriously prone to physical damage.

MJP Proxwitches also have a number of features that distinguish them from less sophisticated capacitive devices:-
1. Built in power supply, just connect up to mains or battery depending on specified voltage. 230v ac, 110/120v ac, 30v ac/dc, 24v ac/dc, or 12v dc.
2. Solid state detection with no external moving parts, but changeover relay output for full 5 amp resistive load switching. Beware those with transistor output switching (usually 2 wire devices) which is limited to milliamps and needs expensive additional control gear.
3. Special circuitry to enable detection in dusty environments. Others when covered in dust cannot distinguish between the dust and the material to be detected.
4. Equivalent to DOL21R (Proxwitch 2) and DOL33R (Proxwitch 3)