VEGA Capacitive electrodes User Manual

Level and Pressure

Operating Instruction

Capacitive electrodes EK …

with signal conditioning instrument

Safety information

Safety information

The described module must only be installed and operated as described in this operating instruction. Please note that other action can cause damage for which VEGA does not take responsibility.

Note Ex-area

Please note the attached approval documents (yellow binder) and especially the included safety data sheet.

2	Capacitive electrodes EK with signal conditioning instrument

Contents

Contents

	Safety information ........................................................................		2
	Note Ex-area ................................................................................		2
1	Product description
	1.1	Function and configuration ..................................................	4
	1.2	Types and versions .............................................................	6
	1.3	Technical data .......................................................................	8
	1.4	Approvals ...........................................................................	14
	1.5	Dimensions .........................................................................	15
	1.6	Type plate ...........................................................................	17
2	Mounting
	2.1	Mounting instructions .........................................................	18
3	Electrical connection
	3.1	Connection instructions .....................................................	23
	3.2	Wiring plan ..........................................................................	24
4	Set-up
	4.1	General adjustment ...........................................................	27
	4.2	Level detection ...................................................................	28
	4.3	Continuous level measurement .........................................	29
5	Diagnosis
	5.1	Simulation ............................................................................	31
	5.2	Maintenance .......................................................................	31
	5.3	Repair ..................................................................................	31
	5.4	Failure removal ...................................................................	32

Capacitive electrodes EK with signal conditioning instrument

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Product description

1 Product description

1.1 Function and configuration

Capacitive electrodes series EK detect levels of virtually any medium, unaffected whether liquids, powders, granules or pastes. This is also valid for adhesive mediums.

The electrode measures also the level capacitance and the ohmic resistance (admittance processing). Hence also problematic mediums and solids with fluctuating humidity contents can be detected.

By the use of screening tubes and screen segments, inactive areas can be provided on the probe where pollution, condensation or permanent build-up do not influence the measuring result.

Measuring principle

Electrode, medium and vessel wall form an electrical capacitor.

The capacitance of the capacitor is mainly influenced by three factors:

-distance of the electrode plates (a)

-size of the electrode plates (b)

-kind of dielectricum between the electrodes (c)

b

c

Fig. 1.1 Plate capacitor (schematic demonstration)

Electrode and vessel wall are the capacitor plates. The medium is the dielectricum. Due to the higher dielectric constant figure (DKvalue) of the medium against air, the capacitance of the capacitor increases with raising covering of the electrode.

Fig. 1.2 Capacitance change with covered electrode

The capacitance change is converted by the oscillator into a level proportional, floating current in the range of 4 … 20 mA or into a switching command.

Continuous level measurement

With the continuous level measurement, the appropriate level is continuously detected and converted into a level proportional signal which is either directly indicated or further processed.

You require a capacitive electrode series EK with oscillator and a signal conditioning instrument VEGAMET, converting the proportional current of the oscillator into standardised current and voltage signals.

The continuous measurement requires a constant dielectric constant figure er, i.e. if possible the medium should have steady features.

4	Capacitive electrodes EK with signal conditioning instrument

Product description

The floating signal of the electrode electronics is in the range 4 … 20 mA and can be therefore connected without additional potential separation to other processing systems such as e.g. VEGALOG.

In addition to the continuous measurement, also levels can be detected (VEGAMET or VEGAMET + VEGASEL).

Level detection

Level switches should signal when certain levels are reached, e.g. max. or min. levels. These levels are detected at a fixed point and converted into a switching command.

For level detection capacitive electrodes EK with appropriate signal conditioning instruments VEGATOR are available. A switching command can be either triggered when the electrode is covered or uncovered.

Capacitive electrodes EK with signal conditioning instrument

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Product description

1.2 Types and versions

			Type*)	EK	EK	EK	EK	EK	EK
Version				11	21	24	26	31	42
Continuous				•	•	•		•	•
Level detection				•	•	•	•	•	•
Partly insulated				•				•
Fully insulated					•	•	•		•
Oscillators
E 14				•	•			•	•
E 15				•	•			•	•
E 15 Ex				•	•			•	•
E 17				•	•			•	•
E 17 Ex				•	•			•	•
E 18				•	•	•	•	•	•
E 18 Ex				•	•	•	•	•	•
Approvals
CENELEC EEx ia IIC T6				•	•	•	•	•	•
PTB-Zone 0 EEx ia IIC T6				•	•	•	•	•	•
Overfill protection
acc. to WHG				•	•	•	•	•	•
German Lloyd1)				•	•	•	•	•	•
Lloyds Register of Shipping1)				•	•	•	•	•	•
American Bureau of Shipping1)				•	•	•	•	•	•
Bureau Veritas1)				•	•	•	•	•	•
RINA1)				•	•	•	•	•	•
Mechanical connection
G 3/		4	A	•	•	•	•	•	•
G 1 A				•	•	•	•	•	•
3/	" NPT			•	•	•	•	•	•
4
1“ NPT				•	•	•	•	•	•
Flange plated					•		•
Electrode material
Steel					•		•
StSt				•2)	•2)	•3)		•4)	•3)
Isolating material5)
PTFE				•	•		•	•
FEP						•			•
PE				•	•			•

6	Capacitive electrodes EK with signal conditioning instrument

Product description

Type*)	EK	EK	EK	EK	EK	EK
Version	11	21	24	26	31	42
Concentric tube
StSt	•	•
Screening tube (option)
StSt	•	•		•	•	•
Temperature adapter
(option)
StSt	•	•		•	•
Housing material
Plastic (IP 66)	•	•	•	•	•	•
Aluminium - plastic coated
(IP 66 and 67)	•	•	•	•	•	•
Others
Bending of
electrode 6)	•	•7)

*) All instrument types also Ex0

1)applied

2)1.4435

3)1.4571

4)1.4401

5)For electrodes certified for Ex-Zone 0, only PTFE and FEP are approved as isolating material.

6)Bending max. 90°

7)EK 21 only with PTFE with 3,2 mm isolation thickness

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				Product description
1.3 Technical data
Housing
Housing material			plastic PBT (Polyester) or Aluminium
			plastic coated
Protection
-	plastic housing		IP 66
-	Aluminium housing		IP 66 and 67 (meets both protections)
Cable entry			1 pce. M20 x 1,5
Terminals			for max. 1,5 mm2 cross-section area of
			conductor
Mechanical connection
Material			1.4435 (316 L)
Thread			G 3/4 A or 3/4“ NPT
			G 1 A or 1“ NPT
Flange			flange versions, plated
Electrode
Material			EK 11	1.4435 (316 L)
			EK 21	steel (St 37), 1.4435 (316 L)
			EK 31	1.4401 (316 L)
			EK 24, 42 1.4571 (316 L)
Length
-	rod		max. 3 m
-	cable		max. 20 m
Isolation			see "Isolating materials"
Max. tensile strength
-	EK 31		3 KN
-	EK 42		3 KN
Ambient conditions
Ambient temperature on the housing			-40°C … +80°C
Medium temperature			see "Product temperature and operating
			pressure"
Storage and transport temperature			-40°C … +80°C
Operating pressure			see "Product temperature and operating
			pressure"
Oscillators E14, E15, E17, E18
Protection class			II
Overvoltage category			III
Meas. frequency			see table on the following page
Capacitance ranges			see table on the following page
Supply voltage			12 … 36 V DC (powered by signal conditioning
			instrument)
Potential separation			min. 500 V DC (except E14)

8	Capacitive electrodes EK with signal conditioning instrument

Product description

For Ex-applications note the permissible electrical connection values stated in the certificate.

Load in W

Supply voltage in V

Accessory

Straining spring of 1.4571 (EK 42, EK 52, EK 53)

-	load	approx. 185 mm (stressed)
-	tensile load	approx. 200 N
Weight
Basic weight (e.g. EK 24)		approx. 0,8 kg
Rod weight		ø 6 mm - 0,23 kg/m
		ø 10 mm - 0,62 kg/m
Cable weight (EK 31)		approx. 40 g/m

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					Product description
Oscillators in two-wire technology for capacitive electrodes EK
Type	Application		Meas. range	Frequency		Signal cond.instr.
E14	Level detection in general		I: 0 … 25 pF	400 kHz		VEGATOR
			II: 0 … 100 pF			VEGALOG
			III: 0 … 400 pF
E15	Level detection in general		I: 0 … 25 pF	400 kHz		VEGATOR
	with potential separation		II: 0 … 100 pF			VEGALOG
			III: 0 … 400 pF
E15 Ex	as E15, however for use in		I: 0 … 25 pF	400 kHz		VEGATOR Ex
	hazardous areas acc. to		II: 0 … 100 pF			VEGALOG 1)
	CENELEC, PTB zone 0 as well as		III: 0 … 400 pF
	zone 1 and StEx zone 10 and as
	part of an overfill protection acc. to
	WHG, (VbF)
E17	Continuous level measurement in		I: 0 … 120 pF	40 kHz		VEGAMET
	general or level detection with		II: 0 … 600 pF			VEGALOG
	potential separation		III: 0 … 3000 pF			(VEGATOR)
E17 Ex	as E17, however for use in		I: 0 … 120 pF	40 kHz		VEGAMET Ex
	hazardous areas acc. to		II: 0 … 600 pF			VEGALOG 1)
	CENELEC, PTB zone 0 as well as		III: 0 … 3000 pF			(VEGATOR Ex)
	zone 1 and StEx zone 10 and as
	part of an overfill protection acc. to
	WHG, (VbF)
E18 2)	Continuous level measurement		I: 0 … 120 pF	470 kHz		VEGAMET
	or level detection with potential		II: 0 … 600 pF			VEGALOG
	separation acc. to the principle of		III: 0 … 3000 pF			(VEGATOR)
	phase selective admittance proces-
	sing especially for adhesive mediums
	and for the use in solids with
	varying humidity
E18 Ex 2)	as E18, however for the use in		I: 0 … 120 pF	470 kHz		VEGAMET Ex
	hazardous areas acc. to		II: 0 … 600 pF			VEGALOG 1)
	CENELEC, PTB zone 0 as well as		III: 0 … 3000 pF			(VEGATOR Ex)
	zone 1 and StEx zone 10 and as
	part of an overfill protection acc. to
	WHG, (VbF)

1)with safety barrier

2)see following page

10	Capacitive electrodes EK with signal conditioning instrument

Product description

Oscillator E18	Level		fully insulated
	measured value
			electrode
The oscillator E18 with the patented process-		15 % vol.
ing (phase selective admittance processing)	+
extends the application range of capacitive	1)
level measurement technology.	– 0 % 5 %	10 %	Solid
			humidity (%)
In conjunction with the fully insulated rod			partly insu-
electrode EK 24 the oscillator E18 compen-
			lated elec-
sates even very conductive build-up.	1) Actual value level		trode
Mounted in an individual rod or cable elec-	Fig. 1.3 Humidity change
trode type EK, E18 ensures also the exact
measurement in solids with varying humidity
contents.

The oscillator E18 processes the measuring currents according to their phase position. Measuring current with a defined phase shifting as they occur with build-up or humidity changes are filtered out.

Humidity change

A humidity change in solids causes a change of the dielectric constant figure (er). In parallel the ohmic value of the medium changes. Due to the change also a phase shifting of the measuring currents is caused.

With a capacitive measurement already lowest humidity changes cause measuring errors. Typical products are e.g. sand, aggregate in the cement industry, hop or plastic granules (after drying).

When using the oscillator E18 humidity changes of 15 % vol. do not influence the accuracy of the measurement. Even layering of product with different humidity does not play a role for the measuring accuracy.

When the humidity contents exceeds 15 % vol., fully and partly insulated electrodes react differently (see also "Fig. 1.3 Humidity change“). Whereby the measured value on fully insulated electrodes raises with steady level, the measured value on partly insulated electrodes drops.

Capacitive electrodes EK with signal conditioning instrument

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