Question 1

Can each pressure transmitter measure any medium?

Accepted Answer

No, the materials stated in the data sheet are to be checked by the customer for resistance.

Question 2

Will a pressure transmitter also work without a power supply?

Accepted Answer

No.

Question 3

Will the pressure transmitter still work properly when the supply voltage is slightly below the minimum specified level?

Accepted Answer

Up to a certain pressure, the pressure transmitter will still provide a correct output signal. If the pressure increases beyond this point, however, the output signal will remain at the same value, since the power supply is not sufficient to drive the output fully.

Question 4

Can the connector be altered?

Accepted Answer

The electrical connection cannot be altered.

Question 5

Can a 3-wire transmitter also work in a 2-wire configuration?

Accepted Answer

No.

Question 6

Can you switch between 4 ... 20 mA and 0 ... 10 V?

Accepted Answer

No, the output signal is defined in the order and cannot be changed.

Question 7

What causes zero point drift?

Accepted Answer

Through the ageing of the electrical components, through temperature and load cycling.

Question 8

What solutions are there against pressure spikes?

Accepted Answer

For this, we recommend a process connection with a reduced pressure port of 0.6 mm or 0.3 mm.

Question 9

What are mechatronic measuring instruments?

Accepted Answer

Where electronic components or assemblies are integrated into mechanical measuring instruments. Thus, there is a purely mechanical on-site display giving either an additional electrical output signal or offering a switch function. The advantage of instruments like this is that, should the power supply or the measuring signal be disrupted or interrupted, the measured value can nevertheless still be read reliably on site.

Question 10

What is the Hall effect?

Accepted Answer

If a constant current is running through a semiconductor component, and this component is then placed in a magnetic field, then a voltage (Hall voltage) is generated within this semiconductor component which is proportional to the strength of the magnetic field.

Question 11

What function does the Hall sensor provide in intelliGAUGE/intelliTHERM instruments?

Accepted Answer

The magnetic field that affects the Hall sensor comes from a moving permanent magnet, that is arranged at a fixed distance from the Hall sensor. Thus the angle of rotation of the permanent magnet in relation to the Hall sensor can be measured. In intelliGAUGE/intelliTHERM instruments a permanent magnet is fixed on the pointer, central to the pointer shaft. When the pointer turns, the magnet turns with it. Thus the angle of the field lines, which run between the two poles of the magnet, changes relative to the Hall sensor. Since for each angle of the field lines to the Hall sensor there is a different field strength, the Hall sensor generates a Hall voltage that is proportional to the angle of rotation of the pointer and thus proportional to the pressure.

Question 12

What do the abbreviations PGT and PGS stand for?

Accepted Answer

Model PGT (Pressure Gauge Transmitter) instruments are mechatronic pressure measuring instruments which display the pressure without needing external power, and simultaneously generate an electronic output signal. Model PGS (Pressure Gauge Switch) instruments are mechatronic pressure measuring instruments which display the pressure without needing external power, and simultaneously offer an electronic switching function.

Question 13

What is a magnetic snap-action contact (model 821)?

Accepted Answer

The magnetic snap-action contact is a mechanical physical contact for switching loads of up to 30 W 50 VA. The signal output is achieved either ahead of or behind the movement of the actual value pointer. To close the circuit, the contact pin of the movable contact arm, just before reaching the set point, is attracted by the action of a permanent magnet mounted on the carrier arm. Through the holding force of the magnet, magnetic snap-action contacts are immune to vibration. To open the circuit, the magnet keeps the contact arm attracted until the restoring force of the measuring element exceeds the magnet's strength and the contact springs open.

Question 14

What is a sliding contact (model 811)?

Accepted Answer

The sliding contact is a mechanical physical contact for switching loads of up to 10 W 18 VA.

Question 15

What is an electronic contact (model 830.E)?

Accepted Answer

Electronic contacts are fitted with non-contact slot sensors. They are especially suitable for oil-filled gauges and should be preferred for low voltages and small DC loads, such as for the signal input for a PLC (programmable logic controller).

Question 16

What is an inductive contact (model 831)?

Accepted Answer

Inductive limit switches in pointer gauges are fitted with non-contact electrical distance sensors (proximity sensors) in accordance with EN 50227. The output signal is determined by the presence or absence of a flag, moved by the actual value pointer within the range of the electromagnetic field of the proximity switch. They are mainly used in hazardous areas.

Question 17

What is a reed contact (model 851)?

Accepted Answer

Reed contacts are often used for switching small voltages and currents, since their hermetically-sealed design, in combination with contacts in inert gas, cannot become corroded on the contact surfaces. Their high reliability and low contact resistance make them suitable for a large number of applications.They include, for example, PLC applications, signal conversion in measuring instruments, signal lights, acoustic signal transmitters and many more.

Question 18

What is an isolating amplifier?

Accepted Answer

The isolating amplifier transmits digital signals from the hazardous area. The signal transmitters can be either sensors per DIN 19234 (NAMUR) or mechanical contacts. The input is securely isolated from the output and the power supply in accordance with DIN EN 50020. The output and the power supply are securely isolate from each other in accordance with DIN EN 50178.

Question 19

What is meant by switching function?

Accepted Answer

Under switching function, we mean the opening or closing of an electrical circuit. Normally-closed contacts (NC, denoted by a 2) interrupt a circuit on rising pressure (clockwise); normally-open contacts (NO, denoted by a 1) close a circuit on rising pressure (clockwise).

Question 20

What is a change-over contact?

Accepted Answer

When the set point is exceeded, simultaneously one circuit is opened (NC) and one circuit is closed (NO). Changeover contacts are denoted by the number 3 (SPDT).

Question 21

What does NAMUR stand for?

Accepted Answer

NAMUR is the abbreviation for "Normenausschuss Mess- und Regeltechnik" (Standards committee for measurement and control).

Question 22

What is ATEX?

Accepted Answer

ATEX is a widespread synonym for the explosion protection directives of the European Union and is derived from the French abbreviation of “Atmosphere Explosible”. There are currently two directives in the field of explosion protection, namely the ATEX product directive, 2014/34/EU, and the ATEX workplace directive, 1999/92/EC.

Question 23

Which standard regulates contact gauges?

Accepted Answer

Sliding and magnetic snap-action contacts fitted in pressure gauges and thermometers with housing diameters of 100 and 160 mm are governed by DIN 16085.

Question 24

Can the zero point of pressure gauges from the PGT family be set by the user?

Accepted Answer

The zero point of the vast majority of pressure gauges can be reset by the user on site whenever they like. The procedures are explained in the operating instructions. Note: Changing the zero point shifts the whole range by the amount of the change zero point in a positive or negative pressure/temperature direction. Normally, it is not necessary to reset the zero point.

Question 25

Can the span of a pressure gauge from the PGT family be set by the user?

Accepted Answer

The span cannot be altered by the user. During production we can, however, provide any required span, even non-linear, for the electronics. Inverted, square or square-root signals are also possible.

Question 26

Why does one have filled pressure gauges?

Accepted Answer

The filling fluid serves as damping for the moving parts within the case. As a result, damage caused by vibration and increased wear on the moving parts can be prevented. Video

Question 27

What can I do if the medium temperature with filled-gauges is over 100 °C [212 °F]?

Accepted Answer

You can use a pressure gauge syphon , a diaphragm seal or a capillary line as an additional cooling element in order to lower the medium temperature.

Question 28

Why can some pressure gauges only be used up to an ambient temperature of 60 °C [140 °F]?

Accepted Answer

If the window of the pressure gauge is made from safety glass, then it can only be used up to an ambient temperature of 60 °C [140 °F]. The safety glass is made from two glass discs. These glass discs are stuck together using a foil. If the temperature rises above 60 °C [140 °F], then the foil blisters. Consequently, the scale will no longer be able to be read reliably.

Question 29

Can I use a window over an ambient temperature of 60 °C?

Accepted Answer

Windows cannot be used at ambient temperatures of over 60 °C, because the plastic parts such as the sealing underneath the glass and the overpressure plug are not designed for higher temperatures. For temperatures up to 60 °C a transparent polycarbonate can be used.

Question 30

When must there be a CE mark on the dial?

Accepted Answer

When the measuring instrument falls under the scope of the pressure equipment directive (PED; ≥ 2900 psi / 200 bar), EMC directive (e.g. intelliGAUGE) or the low voltage directive (e.g. 821 or 851 contacts).

Question 31

What are the "little yellow levers" on the pressure gauge casing for?

Accepted Answer

Pressure gauges for pressure ranges under 363 psi (25 bar) generally have a filling plug with small levers. These yellow levers are closed on delivery, and must be opened on fitting, in order to prevent any possible pressure build-up in the case. This pressure in the case leads to inadmissibly high accuracy deviations for the gauge. Video

Question 32

What is the difference between a standard pressure gauge and a safety pattern version?

Accepted Answer

A safety version (code S3 per EN837) has an additional solid baffle wall welded between the dial and the measuring system. In addition, the case has a back wall that can blow out completely. The window is typically made of laminated safety glass. If a pressure builds up in the housing (e.g. from a rupture in the Bourdon tube), this pressure will exhaust completely through the back wall, which is then ejected from the case by the pressure. A release of pressure through the window cannot occur, so there is no risk to personnel through splinters of flying glass. At WIKA these instruments are specially marked on the dial with an "S" in the circle.

Question 33

Why must the differential pressure in model 7 differential pressure gauges with bourdon tubes not be allowed to be less than 1/6 of the full scale value?

Accepted Answer

For model 7 differential pressure gauges, the static pressure is the same as the full scale value over 270 degrees of rotation. With an expected differential pressure of 15 psi (1 bar) at a static pressure of 145 psi (10 bar), the two hands would only be separated from each other at a distance of approximately 27 degrees. As a result of this, to ensure that readability is still acceptable, the differential pressure should not drop below 1/6 of full scale (approx. 45 degrees).

Question 34

What happens when a model 7 differential pressure gauge with separation diaphragms made of elastomers is operated below the ambient temperature specified in the data sheet?

Accepted Answer

Below the permissible ambient temperatures, the accuracy deteriorates significantly, since the diaphragm (which is either made of FPM / FKM or NBR) stiffens at low temperatures.

Question 35

What is the function of a single-valve block?

Accepted Answer

With upstream pressure equalising valves it is possible to achieve uniform pressure loading from the plus and minus side, to avoid single-sided overpressure loading during both start-up and operation, and also to enable zero point checks during operation.

Question 36

What is the function of a three-way valve block?

Accepted Answer

With upstream pressure equalising valves it is possible to achieve uniform pressure loading from the plus and minus side, to avoid single-sided overpressure loading during both start-up and operation, and also to enable zero point checks during operation.

Question 37

What is the function of a three or five-way valve block?

Accepted Answer

These pressure-equalising valves (with integrated shut-off, purge and vent valves) enable the pressure gauge to be vented on one or both sides and the supply line to be purged.

Question 38

Why are the model 736.11 and 736.51 not generally suitable for aggressive media?

Accepted Answer

The low-pressure (minus side) enters the interior of the display case and thus the dial (Al), pointer (Al), window, etc. are wetted. Only the plus side, which is made up of the capsule gauge interior, is manufactured from stainless steel and is thus resistant to aggressive media.

Question 39

What is the difference between the DIN 19213 and EN 61518?

Accepted Answer

Question 40

How does the measuring system for Model 7 differential pressure gauges with diaphragms behave outside the full scale value?

Accepted Answer

The plus or minus-sided overpressure safety, up to the maximum working pressure (PN40, PN100, PN250, PN400), is achieved through the metallic measuring element support surface arrangement.  Pressures within the permissible overload range leave no lasting damage on the measuring system.

Question 41

What is NAMUR?

Accepted Answer

NAMUR is the abbreviation for "Normenausschuss Mess- und Regeltechnik" (Standards committee for measurement and control).

Question 42

Which instruments are suitable for liquids with small measuring ranges?

Accepted Answer

Diaphragm pressure gauges up to 0.23 psi (16 mbar) are suitable for liquids (through self-emptying of the pressure chamber).

Question 43

What is the Accuracy class?

Accepted Answer

The Accuracy class gives the error limits in percent of the measuring span.

Question 44

When should a restrictor be used?

Accepted Answer

For pressure spikes or sudden pressure loading and unloading.

Question 45

Does the height above sea level have any effect on the measuring result of relative pressure measuring instruments?

Accepted Answer

No, this has no effect, since it is always the pressure differential from ambient that is measured.

Question 46

What does CNG mean?

Accepted Answer

CNG is the abbreviation for Compressed Natural Gas, also Natural Gas (main constituent Methane), that is stored and transported under high pressure in gas cylinders.

Question 47

What does LNG mean?

Accepted Answer

LNG is the abbreviation for Liquefied Natural Gas, also Natural Gas (main constituent Methane), that is liquefied through low temperatures and relatively low pressures and stored and transported in cryotanks.

Question 48

What does LPG mean?

Accepted Answer

LPG is the abbreviation for Liquefied Petroleum Gas (main constituents are Butane and Propane), which is derived from crude oil and is liquefied through relatively low pressures. Often LPG is also known as Autogas.

Question 49

When are diaphragm seals used?

Accepted Answer

For the user, diaphragm seals enable the use of pressure measuring instruments of all sorts also able to be used for the harshest of applications. Examples: The medium is corrosive and the pressure measuring element itself (e.g. the interior of a Bourdon tube) cannot be sufficiently protected against it. The medium is highly viscous and fibrous, thus causing measuring problems due to dead spaces and constrictions in the bores of the pressure measuring instrument (pressure channel, Bourdon tube). The medium has a tendency towards crystallisation or polymerisation. The medium has a very high temperature. As a result, the pressure measuring instrument is strongly heated. The heating leads to a high temperature error in the pressure measurement (i.e. in the display of the measured pressure on the measuring instrument). It can also exceed the upper limits for the thermal loading of the instrument components. The pressure measuring point is in an awkward location. For space reasons, the pressure measuring instrument either cannot be installed or can only be read poorly. By installing a diaphragm seal and using a longer capillary, the pressure gauge can be installed in a location where it can be easily viewed. In the manufacture of the process product, and in the production plant, hygienic requirements must be followed. For these reasons, dead-space in the measuring instrument and fittings must be avoided. The medium is toxic or harmful to the environment. It cannot be allowed to escape into the atmosphere or environment through leakage. On the grounds of safety and environmental protection, the appropriate protective measures must therefore be taken.

Question 50

What is a diaphragm seal?

Accepted Answer

Diaphragm seals are mounted to existing connections. Usually the connections consist of T-pieces which are integrated into a pipeline, or of welding sockets which are welded to a pipeline, the process reactor or a tank.

Question 51

What is a diaphragm in-line seal?

Accepted Answer

The diaphragm in-line seal is perfectly suited for use with flowing media. With the seal being completely integrated into the process line, measurements are not affected by any turbulence, corners, dead spaces or other obstructions in the flow direction. The medium flows unhindered and effects the self-cleaning of the measuring chamber. The diaphragm seal consists of a cylindrical cover component which contains a welded-in thin-wall round-pipe diaphragm. This makes the designing of special measuring point connections unnecessary. Different nominal widths allow the in-line diaphragm seals to be adapted to the corresponding pipe cross-section. The pressure range goes up to a maximum of 400 bar for PN 6 ... PN 400 flange connections, with the normal temperature limit being at +752 °F (+400 °C).

Question 52

What is a capsule-type diaphragm seal?

Accepted Answer

This type is especially suitable for heterogeneous media, since it is inserted directly into the medium. It has a particularly small space requirement in comparison to other diaphragm seals. The pressure is captured 'at a point'. The seal consists of an oval tube, closed at one end, as a pressure sensor and a connector part welded to it.  To stabilise it, the sensor is mounted to a fitting.  The adaptation to the measuring point is made using female or male threads.

Question 53

Why is the PTFE version limited to a maximum of 260 °C at ≤ 100 bar?

Accepted Answer

PTFE “flows”. Therefore the maximum pressure and temperature is reduced.

Question 54

How thick is the PTFE coating on the diaphragm?

Accepted Answer

0.25 mm.

Question 55

What is the total layer thickness (primer and coating) of the PFA coating on the diaphragm of diaphragm seals?

Accepted Answer

The total layer thickness of the PFA coating on the diaphragm of diaphragm seals is: Stainless steel with PFA FDA (green): 35 ... 72 µm Stainless steel with PFA anti-static (black): 30 ... 112 µm

Question 56

How can one cross-reference flanges to ISO 7005-1 to EN and ASME?

Accepted Answer

DN 50 ISO PN 20 = DN 2" Class 150 ASME B16.5 DN 50 ISO PN 50 = DN 2" Class 300 ASME B16.5 DN 80 ISO PN 20 = DN 3" Class 150 ASME B16.5 DN 80 ISO PN 50 = DN 3" Class 300 ASME B16.5 DN 50 ISO PN 10-40 = DN 50 PN 10-40 EN 1092-1 DN 80 ISO PN 40 = DN 80 PN 40 EN 1092-1

Question 57

What is the accuracy of a diaphragm seal system?

Accepted Answer

The accuracy depends, first and foremost, on the attached measuring instrument (i.e, an attached pressure gauge with a Class 1.0 gives an accuracy of the seal system of 1 % at reference conditions).  At best, it can be 0.1 %.  There are also temperature effects, which can be calculated with the DSC program (Diaphragm Seal Calculation program).

Question 58

Which diaphragm seals are EHEDG certified?

Accepted Answer

Diaphragm seals: 990.18 , 990.22 , 990.24 , 990.50 , 990.51 , 990.52 , 990.53 In-line diaphragm seals: 981.18 , 981.22 , 981.50 , 981.51 , 981.52 , 981.53

Question 59

How does a resistance thermometer work?

Accepted Answer

The electrical resistance of a resistance thermometer's sensor changes with the temperature. As the resistance of measuring resistors to EN 60751 (2009-05) increases with rising temperature, we refer to it as PTC (Positive Temperature Coefficient). Pt100 or Pt1000 measuring resistors are normally used for industrial applications. The thermometers based around EN 60751 are defined in DIN 43735. Video

Question 60

What does „Intercrystalline corrosion" mean?

Accepted Answer

IC (Intercrystalline Corrosion) is a form of corrosion that can occur in most alloys at the appropriate conditions. It is also known as "grain disintegration" or „chromium depletion" The corrosion takes place along the grain boundaries. In steels alloyed with chromium, the chromium contained in the material combines on heating (often while welding) with the carbon to form chromium carbide.  Thus the chromium is no longer available for corrosion protection (formation of a passive layer) in the heated area. This occurs particularly in high-carbon steels. With corrosion-resistant steels, such as 1.4571 (AISI 316Ti), the binding of carbon with titanium or niobium to niobium or titanium carbide (stabilised steels) or lowering the carbon content, e.g. 1.4404 (AISI 316L) acts against IC. These measures prevent the harmful reduction of chromium content along the grain boundaries.

Question 61

What do the Zones in explosion protection mean?

Accepted Answer

Gases: Zone 0 (Category 1): permanent or long-term danger of explosions Zone 1 (Category 2): hazardous atmosphere occasionally exists Zone 2 (Category 3): explosive atmosphere exists only rarely, and then only for a short time Dusts: Zones 20, 21, 22 with the same meanings

Question 62

What do the designations of Temperature Class mean?

Accepted Answer

The ignition temperature is the lowest temperature at which an inflammable mixture of gases can ignite at a flame, a hot surface or otherwise generated spark. Gases and vapours are divided into Classes in which the temperature of the surface must always be lower than that of the mixture. (T1 > 450 °C, T2 > 300 °C, T3 > 200 °C, T4 > 135 °C, T5 > 100 °C, T6 > 85 °C)

Question 63

What does „Pt100“ mean?

Accepted Answer

Pt stands for Platinum with a nominal resistance of 100 Ohm at 0 °C (EN 60751).

Question 64

What does „negative temperature coefficient thermistor“ mean?

Accepted Answer

Negative temperature coefficient thermistors conduct electricity better at higher temperatures than at lower temperatures. They are also known as NTC resistances (Negative Temperature Coefficient). Typically, NTC is used in the plastics and food and beverage industries.

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