Introduction

Inverse frequency shift capacitance point level and continuous level switches are designed to withstand the harsh environments of high pressure and high temperature applications.

Inverse Frequency Technology

Siemens Milltronics inverse frequency shift capacitance instruments incorporate a unique frequency-based approach to level measurement. The capacitance units monitor the effect of capacitance based on frequency change. The relationship between capacitance and frequency is inverse. Because small level changes result in a large frequency change, the result is excellent resolution and accuracy.

Principle of Operation

Inverse frequency shift capacitance instruments require two components: a reference electrode of a variable capacitor, and the measurement electrode. In capacitive level measurement, the environment (typically the vessel wall) acts as the reference electrode, while the probe supplies the measurement electrode. The dielectric is composed of the vessel contents, and, if the measurement electrode is insulated, the insulating layer.

Inverse frequency shift capacitance operation

Capacitance is affected by the surface area of the electrodes, the separation distance between the electrodes, and the dielectric constant of the vessel contents. The dielectric constant is the measure of a material’s ability to store energy. The relative dielectric constant of air (vacuum) is 1: all other materials have a higher value.

Область применения

Application Data Sheet

Способ действия

Common Terms

Capacitance

The property of a system of conductors and dielectrics that permit the storage of electricity when a potential difference exists between the conductors. Its value is expressed as the ratio of a quantity of electricity to a potetial difference, and the unit is a Farad.

Capacitor

A device in a circuit that has the potential to store an electric charge. Typically a capacitor has 2 conductors or electrodes separated by a layer of a nonconducting material called a dielectric. With the conductors on opposite sites of the dielectric layer oppositely charged by a source of voltage, the electrical energy of the charged system is stored in the polarized dielectric.

Dielectric constant

The ability of a dielectric to store electrical potential energy under the influence of an electric field. This is measured by a ratio which compares the capacitance of a condenser with the material as dielectric to its capacitance with a vacuum/dry air as dielectric: the dielectric constant of air is 1.

Active shield

The portion of the probe isolated from the active measurement section. The sensor signal is connected to the active shield portion of the probe, eliminating the electrical potential difference between the shield and the measurement section. So, the shield portion of the probe near the process connection is not affected by changes in vapour concentration, material build-up, dust or condensation.

Технические данные

	Point Level Measurement				Continuous Level/Interface Measurement		Product Detection/Interface Measurement
Criteria	Pointek CLS 100	Pointek CLS 200	Pointek CLS 300	Pointek CLS 500	SITRANS LC 300	SITRANS LC 500	SITRANS PD 500
Typical applications	liquids, slurries, powders, granules, food and pharmaceuticals, petrochemicals	liquids, slurries, powders, granules, relatively high pressure and temperature, hazardous areas	liquids, slurries, powders, granules, relatively high pressure and temperature, hazardous areas	water in oil level, foam or liquid/foam level, glycol regnerators, high-pressure coalescers	conductive or non-conductive liquids, foam or liquid/foam levels, water in oil levels	water in oil, foam or liquid/foam level, high-pressure coalescers, LNG (Liquified Natural Gas)	high temperature/high pressure and highly toxic and agressive chemical environments, off-shore and FPSO vessels
Max. length including sensor	100 mm (4”)	Rod: 5.5 m (18 ft) Cable: up to 35 m (115 ft)	Rod: 1 m (40“) Cable: 25 m (82 ft)	Rod: 1 m (40”)	Rod: 5.5 m (18 ft) Cable: 25 m (82 ft)	Rod: 5.5 m (18 ft) Cable: 35 m (115 ft)	Fitting length: 55 mm (2.1”)
Process Temperature	-40 to 100 °C (-40 to 212 °F)	-40 to 85 °C (-40 to 185 °F) With temp. ext.: -40 to 125 °C (-40 to 257 °F)	-40 to 200 °C (-40 to 392 °F) HT version: -40 to 400 °C (-40 to 752 °F)	-50 to 200 °C (-58 to 392 °F) HT version: -40 to 400 °C (-40 to 752 °F)	-20 to 200 °C (-4 to 392 °F)	-40 to 200 °C (-40 to 392 °F) Optional from -200 to 400 °C (-328 to 752 °F)	-40 to 200 °C (-40 to 392 °F) Optional from -200 to 400 °C (-328 to 752 °F)
Process Pressure	Up to 10 bar g (146 psi g)	Rod and ext. versions: Up to 25 bar g (365 psi g) Cable version: Up to 10 bar g(150 psi g)	Up to 35 bar g (511 psi g)	Up to 50 bar g (725 psi g) HP version: Up to 525 bar g (7665 psi g)	Up to 35 bar g (511 psi g)	Up to 200 bar (2920 psi) Option: up to 525 bar (7665 psi)	Up to 50 bar (725 psi) Option: up to 200 bar (2920 psi)
Output	4 to 20/20 to 4 mA 2-wire current loop Solid state output (stainless steel cable or enclosure version) Relay output (fully-synthetic version)	CLS 200 Analog: 1 Form ’C’ (SPDT) relay, solid-state switch CLS 200 Digital: relay optional, solid-state switch included	CLS 300 Analog: 1 Form ’C’ (SPDT) relay, solid-state switch CLS 300 Digital: relay optional, solid-state switch included	4 to 20/20 to 4 mA 2-wire current loop Solid state switch	4 to 20/20 to 4 mA 2-wire current loop	4 to 20/20 to 4 mA 2-wire current loop Solid state switch	4 to 20/20 to 4 mA 2-wire current loop Solid state switch
Communications		CLS 200 Analog: 3 LED indicators CLS 200 Digital: PROFIBUS PA optional SIMATIC PDM compatible	CLS 300 Digital: PROFIBUS PA optional SIMATIC PDM compatible	HART, SIMATIC PDM compatible		HART	HART
Power Specifications	Standard: 12 to 33 V DC IS: 10 to 30 V DC	CLS 200 Analog: 12 to 250 V AC/DC, 50/60 Hz, 2 VA/2W max. CLS 200 Digital: bus voltage: 9 to 32 V DC, IS version 9 to 24 V DC current consumption: 12.5 mA	CLS 300 Analog: 12 to 250 V AC/DC, 50/60 Hz, 2 VA/2W max. CLS 300 Digital: bus voltage: 9 to 32 V DC, IS version 9 to 24 V DC current consumption: 12.5 mA	12 to 33 V DC (30 V DC for IS) at 3.6 mA, 9.5 to 33 V DC, (30 V DC for IS) at 22 mA 3.6 to 22 mA/22 to 3.6 mA (2-wire current loop)	9 to 32 V DC any polarity, 2-wire current loop circuit (9 V at 22 mA)	12 to 33 V DC (30 V DC for IS) at 3.6 mA, 9.5 to 33 V DC (30 VDC) at 22 mA 3.6 to 22 mA/22 to 3.6 mA (2-wire current loop	12 to 33 V DC (30 V DC for IS) at 3.6 mA, 9.5 to 33 V DC (30 VDC) at 22 mA 3.6 to 22 mA/22 to 3.6 mA (2-wire current loop
Approvals	CE, CSA, FM, ATEX, Lloyd’s Register, WHG	CE, CSA, FM, ATEX, 3A, Lloyd’s Register, WHG	CE, CSA, FM, ATEX, Lloyd’s Register, WHG	CE, CSA_NRTL/C, FM, ATEX, Lloyd’s Register, WHG Current Signalling according to NAMUR NE 43	CE, CSA_NRTL/C, FM, ATEX, Lloyd’s Register, WHG Current Signalling according to NAMUR NE 43	CE, CSA_NRTL/C, FM, ATEX, Lloyd’s Register, WHG Current Signalling according to NAMUR NE 43	CE, CSA_NRTL/C, FM, ATEX, Lloyd’s Register, WHG Current Signalling according to NAMUR NE 43