Level switches (controllers) for liquid levels limit states and other physical quantities, type SPC - 1K including DPZ-2R... two-state impedance converters (relays) and CZP-1... electrode level sensors (probes) Users manual No. 060323MCE Edition. 25.04.2006 (acc. to 040430 09.11.2004) Fig. 1 SPC-1K level switches view of selected unit types 1 Application SPC-1K level switches are intended for use in signalling circuits and/or control of levels of media such as: water, waste water, pulps, syrups, emulsions, chemicals, drinks, milk, coal, wet sand and soil, moulding sand, farm produces etc. Do not use for fuels, oils, places where explosion hazard is present etc. Intended for use in facilities such as: wells, pipelines, reactors and chemicals containers, sink basins and water discharge basins, intermediate pumping stations and oil traps for waste water, rooms with threat of flooding, pressure expansion vessels, boilers, autoclaves, silos etc. The converters are intended for permanent incorporation into protective cabinets or housings while the sensors are designated for permanent installation in the unit where the medium level or presence (or absence) is to be signalled. Detailed circuit and environmental conditions in which the level switch can be used are based on the further information and parameters to be followed. The level switch and/or its assemblies are components intended for signalling and control systems. Before they are used a relevant technical design must be prepared to associate the level switch with the object and other components indispensable for the performance of the necessary functions. The design should be prepared by a specialist (e.g. an electrician) holding the necessary licenses. Both the design and the execution must meet the requirements and recommendations indicated in this manual and the requirements and recommendations of the regulations in force for the individual object. The circuit made according to the design should guarantee the safety of people, animals, property and environment. 2 Operation The operation of the level switch is based on the impact of the of the sensor electrode with the electricity-conducting medium on the electric resistance (impedance) of that electrode against the container walls (or the counterelectrode). 2 3 Design SPC-1K level switch is a selected set composed of an electrode level sensor, CZP-1 type (Fig. 3) and a two-state impedance converter DPZ-2R type (feeder-relay) - (Fig. 2). Sensor (Fig. 3) has a casing with taper pipe or metric thread. A special electrode is embedded in the casing, properly isolated from the casing, with a thread clamp for connecting a conductor. The clamp is shielded with a heat-resistant flexible cap. Fig. 2 Dimensions of DPZ-2R converter including PZ11 type Fig. 3 Dimensions of CZP-1 R1/4 sensor Relpol socket. (basic version) The design of the converter (Fig. 2) is of a block type with a multipin (11-pin block) intended for standard 11-contact sockets (PZ-11 socket of Relpol- ary is required or other socket with identical arrangement of terminals and of not worse electrical parameters). Schematic and block diagrams of the entire level switch in two basic application circuits and the application functions of those circuits are illustrated in figures 4 and 5. The electric circuit can be powered from 230V AC network or with 24V AC current (terminals 4,5) or 12 or 24 V DC current (via internal converter power supply: terminal 4: + , 5: ). Input circuits (terminals 9,10,11,1,2,3) are isolated from the power supply by a low-power separating transformer (Tr) (also where DC is used). The circuit includes a transistor-based detecting amplifier (Wd) and a bistable amplifier (Wp) with hysteresis (flip-flop), output control relay (P) and signal lamps (optical level switches) (Sz) and (Sc) The detecting amplifier (Wd) is interfaced with the bistable amplifier (Wp) by a delay element composed of a resistor (Ro) and a delay capacitor (Co). The switching delay can be increased using an external capacitor (Cd). The delay value without the use of the Cd capacitor is optimal for most of the applications. Auxiliary alternative voltage (Up) is derived from the secondary winding of the separating transformer (Tr) and supplied to a measuring divider formed of an internal range resistor (Rzk) and an external range resistor (Rd) and the measured impedance of the CZP-1sensor. The divider tap is connected to the input of the detecting amplifier (Wd). The control impedance that co- forms the measuring divider (the impedance of the CZP-1sensor) has an impact, depending on its value, on the level of the alternating output voltage of the detecting amplifier (Wd) and hence it correspondingly biases the flip-flop (Wd). The control impedance values for which the relay states are changed (equal to switching resistance values) are a result of the total value of the internal range resistor (Rzk) and the additional range resistor (Rd) (and optionally an additional reducing resistor Rdr connected to the terminals 2-11). The value of the internal range resistor (Rzk) (7.5 k) is selected so as to allow the level switch to meet the requirements of the most of typical applications with a zero value of the additional external range resistor (Rd). The flip-flop switching points (expressed as switching resistance values) are selected in such a way that their average arithmetic value (median threshold) for both basic application circuits (Fig. 4 and 5) is approximately the same. Consequently, the switching resistance values for a specified Rd value, for both application circuits, are the same (this simplifies the selection of the Rd resistor). The flip-flop (Wp) controls the output electromagnetic relay (P) including 1 pair of switching contacts constituting a voltage- free output of the entire level switch and controls the signal lamps (optical level switches). The red lamp (Sc) goes on when the electromagnetic relay is energized while the green lamp (Sz) goes on to indicate that the relay is de-energized (it is the other way round for DPZ-2Rzp version).